AOSpine Masters Series, Volume 5: Cervical Spine Trauma [1 ed.] 9781626232242

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AOSpine Masters Series Cervical Spine Trauma

AOSpine Masters Series Cervical Spine Trauma

Series Editor:

Luiz Roberto Vialle, MD, PhD

Professor of Orthopedics, School of Medicine Catholic University of Parana State Spine Unit Curitiba, Brazil

Guest Editors: F. Cumhur Oner, MD

Professor Spinal Surgery University Medical Center Utrecht Utrecht, The Netherlands

Alexander R. Vaccaro, MD, PhD

Richard H. Rothman Professor and Chairman Department of Orthopaedic Surgery Professor of Neurosurgery Co-Director, Delaware Valley Spinal Cord Injury Center Co-Chief of Spine Surgery Sidney Kimmel Medical Center at Thomas Jefferson University President, Rothman Institute Philadelphia, Pennsylvania With 109 figures

Thieme New York • Stuttgart • Delhi • Rio de Janeiro

Thieme Medical Publishers, Inc. 333 Seventh Ave. New York, NY 10001 Executive Editor: William Lamsback Managing Editor: Sarah Landis Director, Editorial Services: Mary Jo Casey Editorial Assistant: Haley Paskalides Production Editor: Barbara A. Chernow International Production Director: Andreas Schabert Vice President, Editorial and E-Product Development: Vera Spillner International Marketing Director: Fiona Henderson International Sales Director: Louisa Turrell Director of Sales, North America: Mike Roseman Senior Vice President and Chief Operating Officer: Sarah Vanderbilt President: Brian D. Scanlan Compositor: Carol Pierson, Chernow Editorial Services, Inc. Library of Congress Cataloging-in-Publication Data AOSpine masters series. V. 5, Cervical spine trauma / editors, Luiz Roberto Vialle, F. Cumhur Oner, Alexander R. Vaccaro.    p. ; cm.   Cervical spine trauma   Includes bibliographical references and index.   ISBN 978-1-62623-223-5 (alk. paper) — ISBN 978-1-62623-224-2 (eBook)   I. Vialle, Luiz Roberto. editor.  II. Oner, F. Cumhur, editor.  III. Vaccaro, Alexander R., editor.  IV. AOSpine International (Firm)  V. Title: Cervical spine trauma.   [DNLM:  1. Spinal Injuries—diagnosis.  2. Cervical Vertebrae—injuries.  3. Orthopedic Procedures— methods.  4. Spinal Injuries—therapy. WE 725]  RD594.3  617.4'82044—dc23 2015008433 Copyright ©2015 by Thieme Medical Publishers, Inc. Important note: Medicine is an ever-changing science undergoing continual development. Research and clinical experience are continually expanding our knowledge, in particular our knowledge of proper treatment and drug therapy. Insofar as this book mentions any dosage or application, readers may rest assured that the authors, editors, and publishers have made every effort to ensure that such references are in accordance with the state of knowledge at the time of production of the book. Nevertheless, this does not involve, imply, or express any guarantee or responsibility on the part of the publishers in respect to any dosage instructions and forms of applications stated in the book. Every user is requested to examine carefully the manufacturers’ leaflets accompanying each drug and to check, if necessary in consultation with a physician or specialist, whether the dosage schedules mentioned therein or the contraindications stated by the manufacturers differ from the statements made in the present book. Such examination is particularly important with drugs that are eitherrarely used or have been newly released on the market. Every dosage schedule or every form of application used is entirely at the user’s own risk and responsibility. The authors and publishers request every user to report to the publishers any discrepancies or inaccuracies noticed. If errors in this work are found after publication, errata will be posted at www.thieme.com on the product description page. Some of the product names, patents, and registered designs referred to in this book are in fact registered trademarks or proprietary names even though specific reference to this fact is not always made in the text. Therefore, the appearance of a name without designation as proprietary is not to be construed as a representation by the publisher that it is in the public domain. Printed in China by Everbest Printing Ltd. 5 4 3 2 1 ISBN 978-1-62623-223-5 Also available as an e-book: eISBN 978-1-62623-224-2

AOSpine Masters Series Luiz Roberto Vialle, MD, PhD Series Editor

Volume 1

Metastatic Spinal Tumors

Volume 2

Primary Spinal Tumors

Volume 3

Cervical Degenerative Conditions

Volume 4

Adult Spinal Deformities

Volume 5

Cervical Spine Trauma

Volume 6

Thoracolumbar Spine Trauma

Volume 7

SCI and Regeneration

Volume 8

Back Pain

Volume 9

Pediatric Spinal Deformities

Volume 10

Spinal Infection

Contents

Series Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix Luiz Roberto Vialle Guest Editors’ Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi F. Cumhur Oner and Alexander R. Vaccaro  1 Anatomy of the Cervical Spine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Ronald L.A.W. Bleys  2 Biomechanics of the Cervical Spine: From the Normal State to the Injury State. . . . . . . . . . . 17 Ahmer K. Ghori, Dana Leonard, and Thomas Cha  3 Evaluation of an Injured Cervical Spine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Richard Assaker, Fahed Zairi, and Xavier Demondion  4 Nonoperative Management of Cervical Spine Trauma. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Peter Formby and Melvin D. Helgeson  5 Occipital Condyle Fractures and Occipitocervical Dissociation. . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Philipp Schleicher, Matti Scholz, and Frank Kandziora  6 Atlas Injuries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Matti Scholz, Philipp Schleicher, and Frank Kandziora  7 Odontoid Fractures, Hangman’s Fractures, and C2 Body Fractures . . . . . . . . . . . . . . . . . . . . . . . 73 Wilco C. Peul and Carmen L.A. Vleggeert-Lankamp  8 Compression (AO Type-A Injuries). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 Nuno Neves  9 Subaxial Cervical Spine Injuries: Distraction (AO Type-B Injuries) . . . . . . . . . . . . . . . . . . . . . . . 94 William A. Robinson, Kevin P. McCarthy, Alexander R. Vaccaro, and C. Chambliss Harrod 10 Facet and Lateral Mass Fractures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 Máximo-Alberto Díez-Ulloa



viii Contents 11 Cervical Dislocations (AO Type-C Injuries). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 William Muñoz, Michael J. Vives, and Saad B. Chaudhary 12 Cervicothoracic Junction Injuries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 Ripul Rajen Panchal 13 Cervical Trauma in Combination with Ankylosing Spondylitis or Diffuse Idiopathic Skeletal Hyperostosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 Jorrit-Jan Verlaan and F. Cumhur Oner 14 Rheumatoid Arthritis and Osteoporosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 David T. Anderson 15 Pediatric Cervical Spine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 Ahmet Alanay and Caglar Yilgor 16 The New AOSpine Subaxial Cervical Spine Injury Classification System . . . . . . . . . . . . . . . . . 169 Gregory D. Schroeder, Paul M. Millhouse, Alexander R. Vaccaro, F. Cumhur Oner, and Luiz Roberto Vialle Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

Series Preface

Spine care is advancing at a rapid pace. The challenge for today’s spine care professional is to quickly synthesize the best available evidence and expert opinion in the management of spine pathologies. The AOSpine Masters ­Series provides just that—each volume in the series delivers pathology-focused expert opinion on procedures, diagnosis, clinical wisdom, and pitfalls, and highlights today’s top research papers. To bring the value of its masters level edu­ cational courses and academic congresses to a wider audience, AOSpine has assembled internationally recognized spine pathology leaders to develop volumes in this Masters Series as a

vehicle for sharing their experiences and expertise and providing links to the literature. Each volume focuses on a current compelling and sometimes controversial topic in spine care. The unique and efficient format of the ­Masters Series volumes quickly focuses the attention of the reader on the core information critical to understanding the topic, while encouraging the reader to look further into the recommended literature. Through this approach, AOSpine is advancing spine care worldwide. Luiz Roberto Vialle, MD, PhD

Guest Editors’ Preface

The diagnosis and treatment of traumatic cervical spine injuries is a rapidly evolving field. Advances in imaging and critical care, together with the development of specific instrumentation and surgical techniques, now enable patients to survive many once-fatal injuries. However, the failure to recognize these injuries and treat them properly can have catastrophic consequences. Many of these injuries are associated with neurologic impairment, and advances in our understanding of the primary and secondary mechanism of spinal cord injuries has made the importance of early surgical decompression and stabilization universally accepted. Thus, it is paramount that all spine surgeons be prepared to properly diagnose and treat patients with these injuries rapidly. Although in the past spinal injuries were usually a result of high-energy trauma and were relegated to a few specialized treatment centers, with the aging of the population, many

elderly patients are presenting to community hospital emergency rooms with cervical spine injuries from low-energy falls. This book will help spine surgeons feel comfortable in managing these complex cases. This book offers detailed analyses of the essential aspects of the most common injuries to both the upper and lower (subaxial) cervical spine. World-renowned experts discuss the anatomy, biomechanics, patient evaluation, and critical steps in the decision-making process for the treatment of these complex injuries. The authors of each chapter both discuss the historic literature and present a synthesized analysis of the current literature and their own clinical experience. They also propose treatment algorithms that are based on the best available evidence. F. Cumhur Oner, MD Alexander R. Vaccaro, MD, PhD

Contributors

Ahmet Alanay, MD Professor Department of Orthopedics and Traumatology Faculty of Medicine Acibadem University Istanbul, Turkey David T. Anderson, MD Orthopaedic Spine Surgeon OrthoCarolina Charlotte, North Carolina Richard Assaker, MD, PhD Professor Department of Neurosurgery Centre Hospitalier Regional Universitaire de Lille Clinque de Neurochirurgie Lille, France Ronald L.A.W. Bleys, MD, PhD Professor of Anatomy Department of Anatomy University Medical Center Utrecht Utrecht, The Netherlands Thomas Cha, MD, MBA Orthopaedic Spine Center Boston, Massachusetts

Saad B. Chaudhary, MD, MBA Assistant Professor Department of Orthopaedics Mount Sinai Beth Israel New York, New York Xavier Demondion, MD, PhD Professor Musculoskeletal Department of Radiology Centre Hospitalier Regional Universitaire de Lille Lille, France Máximo-Alberto Díez-Ulloa, MD Associate Professor Doctor in Medicine and Surgery University of Santiago de Compostela Orthopaedics and Traumatology Service Universitary Hospitalary Complex of Santiago de Compostela Santiago de Compostela, Spain Peter M. Formby, MD Resident Department of Orthopaedics Walter Reed National Military Medical Center Bethesda, Maryland



xiv Contributors Ahmer K. Ghori, MD Chief Resident Harvard Orthopaedic Surgery Residency Department of Orthopaedic Surgery Massachusetts General Hospital Boston, Massachusetts

William Muñoz, MD Resident Department of Orthopaedics Rutgers New Jersey Medical School Doctor’s Office Center Newark, New Jersey

C. Chambliss Harrod, MD Attending Spinal Surgeon Bone and Joint Clinic of Baton Rouge Baton Rouge, Louisiana

Nuno Neves, MD Orthopedic Surgeon Spine Group Orthopedic Department Centro Hospitalar São João Faculty of Medicine, University of Porto Porto, Portugal

Melvin D. Helgeson, MD Chief Pediatric and Spine Surgery Service Department of Orthopaedic Surgery Walter Reed National Military Medical Center Orthopaedics Department Bethesda, Maryland Frank Kandziora, MD, PhD Head of Department Center for Spinal Surgery and Neurotraumatology Zentrum für Wirbelsäulenchirurgie und Neurotraumatologie Berufsgenossenschaftliche Unfallklinik Frankfurt am Main, Germany Dana Leonard, BA Clinical Research Coordinator Department of Orthopaedic Surgery Brigham and Women’s Hospital Boston, Massachusetts Kevin P. McCarthy, MD Bone and Joint Clinic Baton Rouge, Louisiana Paul W. Millhouse, MD Rothman Institute Thomas Jefferson University Philadelphia, Pennsylvania

F. Cumhur Oner, MD Professor Spinal Surgery University Medical Center Utrecht Utrecht, The Netherlands Ripul Rajen Panchal, DO Assistant Professor Department of Neurological Surgery University of California Davis Medical Group Sacramento, California Wilco C. Peul, MD, PhD Director Spine Intervention Prognostic Study Group Leiden University Medical Center Medical Center Haaglanden The Hague, The Netherlands William A. Robinson, MD Resident Physician Department of Orthopaedic Surgery The Mayo Clinic Rochester, Minnesota Philipp Schleicher, MD Fellow Center for Spinal Surgery and Neurotraumatology Berufsgenossenschaftliche Unfallklinik Frankfurt am Main, Germany

Contributors Matti Scholz, MD Senior Consultant Department for Trauma and Orthopaedic Surgery Berufsgenossenschaftliche Unfallklinik Frankfurt am Main, Germany Gregory D. Schroeder, MD Rothman Institute Thomas Jefferson University Philadelphia, Pennsylvania Alexander R. Vaccaro, MD, PhD Richard H. Rothman Professor and Chairman Department of Orthopaedic Surgery Professor of Neurosurgery Co-Director, Delaware Valley Spinal Cord Injury Center Co-Chief of Spine Surgery Sidney Kimmel Medical Center at Thomas Jefferson University President, Rothman Institute Philadelphia, Pennsylvania Jorrit-Jan Verlaan, MD, PhD Orthopaedic Surgeon University Medical Center Utrecht, The Netherlands Luiz Roberto Vialle, MD, PhD Professor of Orthopedics, School of Medicine Catholic University of Parana State Spine Unit Curitiba, Brazil

Michael J. Vives, MD Associate Professor Chief Spine Division Department of Orthopedics Rutgers New Jersey Medical School Newark, New Jersey Carmen L.A. Vleggeert-Lankamp, MD Department of Neurosurgery Leiden University Medical Center Leiden, The Netherlands Caglar Yilgor, MD Assistant Professor Department of Orthopedics and Traumatology Faculty of Medicine Acibadem University Istanbul, Turkey Fahed Zairi, MD Assistant Professor Department of Neurosurgery Lille University Hospital Lille, France

xv

1 Anatomy of the Cervical Spine Ronald L.A.W. Bleys

■■ Introduction The cervical spine is the part of the vertebral column that extends from the skull to the thorax. It has seven vertebrae, C1 to C7, which are smaller than the vertebrae of the inferior regions due to the fact that they bear less weight. Although the intervertebral disks are also thinner than the thoracic and lumbar disks, they are relatively thick in comparison to the height of the vertebral bodies. This contributes to the mobility of the cervical spine, which is the most mobile part of the vertebral column permitting flexion and extension, lateral flexion, and rotation. The orientation of the articular facets and the relatively small tissue mass surrounding the cervical vertebrae add further to the mobility. Vertebrae C3 to C6 are typical cervical vertebrae. The atlas (C1) and the axis (C2) are atypical, and C7 is different because of its long spinous process. In anterior and posterior surgical approaches to the cervical spine, the course of many important structures should be taken into account. Muscles are more abundant in the posterior region because the center of gravity of the head is anterior to the cervical spine. The posterior muscles are arranged in several layers. In the uppermost posterior region the deep suboccipital muscles are important for posture. Many nerves and blood vessels are closely related to the cervical spine. The spinal nerves emerge from the intervertebral foramina and

the vertebral artery passes through the foramina in the transverse processes. This chapter discusses the general features of the cervical vertebrae, the associated ligaments, the muscles of the back, and the vascular supply of the cervical spine, and describes the upper cervical spine and the subaxial cervical spine in more detail.

■■ General Features Cervical Vertebrae Vertebrae C3 to C7, like the thoracic and the lumbar vertebrae, consist of a vertebral body, a vertebral arch, and seven processes (Fig. 1.1). The bodies are small but broad. The superior surfaces of the bodies are saddle-shaped, with their lateral margins projecting upward as ­uncinate processes. The anterior margin is depressed a bit. On the inferior surface the anterior margin projects down and partly overlaps the anterior aspect of the intervertebral disk. These particular shapes of the surfaces of the bodies limit lateral and anteroposterior gliding movements. The arches are dorsal to the bodies and each one is divided into two pedicles and two laminae. The vertebral foramen between the body and the arch is big and triangular to accommodate the intumescentia cervicalis. This is the cervical enlargement of the spinal cord, which



2

Chapter 1

a

b

Fig. 1.1a,b  (a) Superior and (b) anterior view of the first, second, fourth, and seventh cervical vertebrae. (From Schuenke M, Schulte E, Schumacher U, eds.

Thieme Atlas of Anatomy. General Anatomy and Musculoskeletal System. New York: Thieme; 2006. © Thieme, 2005. Illustration by Karl Wesker.)

is related to the innervation of the upper limb. Superior and inferior to the pedicles are the superior and inferior vertebral notches, which contribute to the boundaries of the intervertebral foramina through which the spinal nerves pass. The seven processes are the two transverse processes, the spinous process, and four articular processes. A distinctive feature of a cervical transverse process is that it has a foramen—the transverse foramen. This reflects the fact that these processes are composed of a ventral part, which is a remnant of a rib anlage, and a dorsal part, which represents the original transverse process. Correspondingly, the transverse process ends laterally in anterior and posterior tubercles. The vertebral arteries typically run through the transverse foramina of the upper six cervical vertebrae. For this reason the foramina of C7 are smaller. The spinous processes of C3 to C6 are bifid and those of C3 to C5 are short. Race and sex differences have been reported because short bifid spinous processes are especially found in white males.1 Vertebra C7 differs from C3 to C6 because it has a long spinous process that is not bifid. This vertebra is called vertebra prominens because in most people it has the most prominent spinous process, which according to many descriptions can be easily palpated, especially when the neck is in flexion. However, because the spinous processes of C6 and T1 have almost similar dimensions, it may be difficult to distinguish among C6, C7, and T1. Vertebrae C1 and C2 are discussed below (see Occiput and Upper Cervical Spine).

Ligaments of the Vertebral Column Vertebrae are connected by numerous ligaments (Fig. 1.2). They can be divided into long bands, which extend along the greatest part of the spine, and shorts bands, which connect adjacent vertebrae. The long bands comprise the anterior longitudinal, the posterior longitudinal, and the supraspinous ligaments. The anterior longitudinal ligament is a strong broad band that connects the anterolateral surfaces of the vertebral bodies. It extends from the occipital bone to the anterior tubercle of C1 and then continues downward to the front of

Anatomy of the Cervical Spine the sacrum. Its uppermost part is relatively narrow. The ligament is most adherent to the intervertebral disks and the adjacent margins of the vertebral bodies. It limits extension of the spine. The posterior longitudinal ligament runs inside the vertebral canal from C2 to the sacrum and connects the posterior surfaces of the vertebral bodies. At lower levels it is broader over the disks than over the bodies, giving it a denticulated appearance. However, in the cervical and upper thoracic regions, it is of uniform width. Its strongest attachments are to the intervertebral disks. From C2 it extends upward as the tectorial membrane to the skull base. The supraspinous ligament is a fibrous cord that connects the tips of the spinous processes from C7 to the sacrum. In the cervical region it expands as the nuchal ligament. The nuchal ligament is structurally different because it is composed of fibroelastic tissue. It is a triangular bilaminar intermuscular septum that runs from the external occipital protuberance to the posterior border of the foramen magnum and from there to the posterior tubercle of C1 and the bifid spinous processes of the remaining cervical vertebrae (Fig. 1.2). Between the laminae is a layer of loose connective tissue. The layers fuse at the free posterior border of the ligament. The nuchal ligament provides attachment for muscles because the spinous processes of C3 to C5 are short. In other animals the ligament is much thicker and is of importance for suspension of the head. The short bands are the interspinous and intertransverse ligaments and the ligamenta flava. The interspinous ligaments are thin bands that connect adjacent spinous processes. The intertransverse ligaments connect adjacent transverse processes. In the cervical region they are inconspicuous and partially replaced by intertransverse muscles. The ligamenta flava are strong yellowish elastic bands that connect the laminae of adjacent vertebrae and thus contribute to the posterior wall of the vertebral canal. They are thick in the thoracic and lumbar regions. In the ­cervical region they are thin, long, and broad, which accommodates the great extent of mobility of the cervical spine. The ligamenta flava

3



4

Chapter 1

Fig. 1.2  Ligaments of the cervical spine as seen in a midsagittal section, left lateral view. (From Schuenke M, Schulte E, Schumacher U, eds. Thieme

Atlas of Anatomy. General Anatomy and Musculoskeletal System. New York: Thieme; 2006. © Thieme, 2005. Illustration by Karl Wesker.)

limit abrupt flexion of the spine and thus resist separation of the vertebral arches. Because of their elastic nature they assist in extension back to an erect posture after flexion. Specific ligaments related to the occipital bone and the upper two cervical vertebrae are discussed below (see Occiput and Upper Cervical Spine).

and Upper Cervical Spine and Subaxial Cervical Spine). The dorsal muscles (Fig. 1.3) form a greater mass than the prevertebral muscles because most body weight is anterior to the spine. Muscles on the posterior side of the spine are not confined only to the cervical region. They are best understood when the musculature of the back is considered as a whole. These muscles are organized into superficial, intermediate, and deep groups. Only the deep muscles are true intrinsic back muscles that specifically act on the spine and are supplied by dorsal rami of the spinal nerves. The superficial and intermediate muscles are extrinsic back muscles. Superficial extrinsic mus-

Muscles of the Back The muscles of the cervical spine are distinguished in prevertebral muscles and the muscles of the back. Prevertebral muscles include the anterior and lateral vertebral muscles, and they are described below (see sections Occiput



Anatomy of the Cervical Spine

cles act on the pectoral girdle and the shoulder joint. They include trapezius, levator scapulae, latissimus dorsi, and rhomboids. Intermediate extrinsic muscles are the superior and inferior serratus posterior, which may aid in respiration. Of all extrinsic muscles, only the trapezius and levator scapulae are found in the cervical region. The intrinsic back muscles also have a multilayered arrangement and are divided ­ into superficial, intermediate and deep layers (Table 1.1). The superficial layer is found only in the cervical and upper thoracic region and consists of the splenius capitis and splenius cervicis. These flat and thick muscles originate from the midline (spinous processes and nuchal ligament) and extend superolaterally to the transverse processes of C1 to C3 (or C4) (splenius cervicis) and the occipital bone and mastoid process (splenius capitis). When left and right muscles act together, they extend the head and neck. When acting alone, they draw and rotate the head to the ipsilateral side and are there-

fore synergistic with the contralateral sternocleidomastoid. The erector spinae forms the intermediate layer. It is a massive muscle complex lying on either side of the vertebral column. It is divided into three columns, which are, from lateral to medial, the iliocostalis, longissimus, and spinalis. Each column is further regionally divided, based on the levels of their superior attachments (Table 1.1). The origins and insertions of the various parts are not discussed here in detail. In the cervical region, deep to the splenius muscles, parts of all columns are found. The erector spinae is the chief extensor of the vertebral column and the head. Acting unilaterally, it bends the spine laterally. The longissimus capitis turns the head to the ipsilateral side. The deep muscles are the transversospinalis group. They lie deep to the erector spinae and are subdivided into semispinalis, multifidus, and rotatores groups, which are further specified according to the levels of their superior attachments (Table 1.1). These muscles run from transverse processes to spinous processes

Table 1.1  The Intrinsic Muscles of the Back Muscle Group

Name of Muscle

Regional Divisions

Superficial layer

Splenius

Intermediate layer (erector spinae)

Iliocostalis

Cervicis Capitis Lumborum Thoracis Cervicis Thoracis Cervicis Capitis Thoracis Cervicis Capitis Thoracis Cervicis Capitis

Longissimus

Spinalis

Deep layer (transversospinalis)

Semispinalis

Multifidus Rotatores

Short muscles

Interspinales Intertransversarii

Lumborum Thoracis Cervicis

5



6

Chapter 1 of more superior vertebrae, hence the name transversospinalis group, and occupy the space between the spinous and transverse processes. Semispinalis muscles bridge four or more vertebrae, multifidus muscles bridge two to four vertebrae, and rotatores muscles bridge two vertebrae or connect adjacent vertebrae. In the cervical region, the semispinalis is well developed. The semispinalis capitis attaches to the occipital bone and is visible as a longitudinal bulge in the neck next to the midline. The semi­ spinalis muscles extend the spine and the head, and, when acting unilaterally, the semi­spinalis capitis turns the head slightly to the contralateral side. Multifidus muscles are important for segmental stabilization during movements of the spine. Rotatores muscles are generally not so well developed in the cervical region. Deep to the transversospinalis group a fourth group is found that consists of the small interspinales and intertransversarii. These short muscles connect the spinous and the transverse processes of adjacent vertebrae, respectively, and like the multifidus muscles are important as segmental stabilizers. The interspinales and intertransversarii are best developed in the cervical region. Here the intertransversarii consist of anterior and posterior muscles, which attach to the anterior and posterior tubercles of the transverse processes. As a consequence, the ventral rami of the spinal nerves pass between the anterior and posterior intertransversarii. Deep to the semispinalis capitis, in the upper part of the neck, the suboccipital muscles are found. These consist of four muscles, which connect the occipital bone, C1 and C2. They occupy the so-called suboccipital region. These muscles are discussed below (see Occiput and Upper Cervical Spine). In a posterior approach to the cervical spine, from superficial to deep, the following muscles are found (Fig. 1.3; see also Fig. 1.5): • Trapezius • Splenius capitis/splenius cervicis • Semispinalis capitis/semispinalis cervicis and longissimus capitis • Multifidus and rotatores • Interspinales and intertransversarii/suboccipital muscles

When the compartment between the layers of the nuchal ligament is opened, easy access to the vertebrae is obtained.

Vascular Supply of the Cervical Spine Unlike in the thoracic and lumbar regions, segmental arteries have not persisted in the cervical region. The cervical vertebrae are supplied by spinal branches from longitudinal arteries that developed from anastomoses between the segmental arteries. These are the vertebral, deep cervical, and ascending cervical arteries. The vertebral artery arises from the subclavian artery and is discussed in the next section. The deep cervical artery originates from the costocervical trunk and ascends behind the transverse processes, between the semispinalis capitis and semispinalis cervicis. The ascending cervical artery is a branch of the inferior thyroid artery and ascends on the anterior tubercles of the transverse processes. Spinal veins form venous plexuses along the entire vertebral column. These plexuses are both outside and inside the vertebral canal, and because they are more abundant anteriorly and posteriorly, it has become customary to term them anterior and posterior internal vertebral venous plexuses and anterior and posterior external vertebral venous plexuses. The internal vertebral venous plexus occupies the epidural space. It is discussed below (see Occiput and Upper Cervical Spine). The plexuses anastomose freely with each other and drain into segmental veins in the thoracic and lumbar regions and into, among others, the vertebral veins on the cervical level.

■■ Occiput and Upper Cervical

Spine

Occipital Bone, Atlas, and Axis The occipital bone has squamous, basilar, and lateral (condylar) parts. The squamous part is the bony plate superoposterior to the foramen magnum. The most visible external fea-



Anatomy of the Cervical Spine

Fig. 1.3  Muscles on the posterior side of the cervical spine. On the left side all muscles are intact. The trapezius, splenius capitis, and semispinalis capitis cover the deep region of the neck. Removal of these muscles (right) gives access to the sub­ occipital region. Four suboccipital muscles connect

the occipital bone, the atlas, and the axis. (From Schuenke M, Schulte E, Schumacher U, eds. Thieme Atlas of Anatomy. General Anatomy and Musculoskeletal System. New York: Thieme; 2006. © Thieme, 2005. Illustration by Karl Wesker.)

tures are the external occipital protuberance and the external occipital crest, which runs down from the protuberance to the foramen magnum. Many muscles attach to this part of

the occipital bone, including the trapezius, the splenius capitis, and the semispinalis capitis. The basilar part extends superoante­riorly from the ­foramen magnum. Its inferior surface

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Chapter 1 provides attachment to the pharynx and a few muscles. Its superior surface contributes to the clivus in the cranial cavity on which the medulla oblongata and the pons rest. The distal parts of the vertebral arteries and the basilar artery run here, too. The two lateral (condylar) parts lie on both sides of the foramen magnum. The occipital condyles are on their inferior surfaces and articulate with the superior facets of the atlas. They are oval or kidney-­ shaped and their long axes converge anteromedially. Above the condyles are the hypoglossal canals. The condylar fossa, a depression behind each condyle, may contain a condylar canal for the passage of an emissary vein. This condylar emissary vein, if present, connects the sigmoid sinus and veins in the suboccipital triangle. Vertebra C1, the atlas (Fig. 1.1), has neither a body nor a spinous process. The ring-shaped bone consists of two lateral masses connected by a short anterior arch and a longer posterior arch. The place of the body is occupied by the dens of C2. During development, the body of C1 fuses with the body of C2 and becomes the dens. For this reason there is no intervertebral disk between C1 and C2. The lateral masses articulate with the occipital bone and bear the weight of the skull. The transverse processes arise from the lateral masses, and therefore they are more laterally placed than those of the other cervical vertebrae. Moreover, the transverse processes themselves are long. For these reasons, C1 is the widest of the cervical vertebrae, and its transverse processes can even be palpated between the ramus of the mandible and the mastoid process. Their positions make them good levers for muscles that keep the head balanced. Each lateral mass has a kidney-­ shaped superior articular facet, which articulates with an occipital condyle. The inferior articular facet is flat and circular and articulates with C2. The anterior arch has an anterior tubercle on its external aspect to which the anterior longitudinal ligament is attached. Its internal aspect carries a facet for the dens. The posterior arch has a posterior tubercle in the midline. This is a rudimentary spinous process to which the nuchal ligament is attached. The superior surface of the posterior arch has a

groove for the vertebral artery. The suboccipital nerve, which is the dorsal ramus of spinal nerve C1, emerges between the vertebral artery and the posterior arch. The strong vertebra C2, the axis (Fig. 1.1), is characterized by the dens, which projects upward from its body and serves as a pivot around which the atlas rotates. In adults, the mean length of the dens is 15 mm. The anterior surface has a facet for the anterior arch of the atlas, whereas on the posterior surface there is a groove for the transverse ligament of the atlas. The body of the axis contains a rudimentary disk, which indicates the fusion between the centra of C1 and C2. The pedicles and the medial part of the transverse processes carry flat superior articular facets on which the atlas rotates. The transverse process projects inferiorly and laterally, and as a consequence the transverse foramen is directed laterally. This permits the vertebral artery to pursue a lateral course to the transverse foramen of the atlas. The axis has thick laminae to which the ligamenta flava attach, and it has a large bifid spinous process.

Joints and Ligaments Together, the joints of the upper cervical spine are called the craniovertebral joints. They connect the occipital bone, the atlas, and the axis, and provide a wide range of movement. Half of the rotation, which can occur in the cervical spine as a whole, takes place between the atlas and the axis. The joints involved are the atlanto-occipital joints and the atlantoaxial joints. They are all synovial joints. The atlanto-occipital joints are articulations between the occipital condyles and the superior articular facets of the lateral masses of the atlas. The surfaces on the condyles are convex, and those on the atlas are concave. The joint capsules are thin and loose, and the joint axes run in an anteromedial direction. Main movements are flexion and extension (nodding of the head), but a few degrees of lateral flexion and rotation are possible as well. The occipital bone and atlas are also connected by the anterior and posterior atlanto-occipital membranes. The anterior atlanto-occipital membrane is broad

and dense and connects the anterior arch of C1 with the anterior margin of the foramen magnum. Medially it is continuous with the anterior longitudinal ligament, and laterally it blends with the joint capsule. The posterior atlanto-occipital membrane is also broad but thin, and it connects the posterior arch of C1 with the posterior margin of the foramen magnum. It also blends with the joint capsules. Because the vertebral arteries occupy grooves on the posterior arch, this membrane arches over the arteries and permits access to the arteries on their way to the cranial cavity. The articular surfaces and the fibrous structures (joint capsule, membranes, and ligaments) are involved in maintaining stability. There is a role for the dorsal neck muscles as well, especially the suboccipital muscles, which are involved in maintaining posture. The atlantoaxial joints are the three articulations between the atlas and the axis. They are two lateral atlantoaxial joints, between the lateral masses of the atlas and the superior ­articular facets of the axis, and the median atlantoaxial joint. The articular surfaces of the lateral joints are nearly flat, permitting gliding movements. In the median atlantoaxial joint the dens articulates with the anterior arch of the atlas in front and with the transverse ligament of the atlas behind. The groove on the posterior surface of the dens has a cartilage covering for this. This joint is a pivot joint, and it permits rotation. As a consequence, the movement of the three joints together is a rotation, the dens being the axis. This results in a rotation of the head of about 40 degrees. Joint capsules of these three joints are loose. During the rotation the dens is held in position by the strong transverse ligament of the atlas, which runs between both lateral masses and forms the posterior wall of the socket for the dens. Its length is ~ 20 mm. It is attached on tubercles on the medial sides of the lateral masses. Where it articulates with the dens it is covered by cartilage. From its upper and lower margins median longitudinal bands run to the occipital bone and the body of C2. Together with the transverse ligament, these superior and inferior longitudinal bands constitute the cruciate ligament of the atlas.

Anatomy of the Cervical Spine There are more ligaments, which connect the axis and the occipital bone. Three of them attach to the dens. From the sides of the dens thick alar ligaments run to the lateral margins of the foramen magnum. These ligaments limit excessive atlantoaxial rotation. From the apex of the dens the apical ligament of the dens fans out into the anterior margin of the foramen magnum. It lies between the anterior atlanto-­ occipital membrane and the cruciate ligament (superior longitudinal band) and is separated from these structures by fat pads. The tectorial membrane is the cranial continuation of the posterior longitudinal ligament. From the body of the axis it runs upward behind the cruciate ligament and attaches to the occipital bone above the anterior margin of the foramen magnum, which actually is the floor of the posterior cranial fossa. Here it blends with the cranial dura mater. Between the tectorial membrane and the cruciate ligament is a thin layer of loose connective tissue. Taken together, passing from outside the anterior side of the spine into the vertebral canal, between the occipital bone and the anterior arch of the atlas/dens of the axis complex, the following layers are crossed in the midline (Fig. 1.2): • Anterior atlanto-occipital membrane and anterior longitudinal ligament • Fat pad • Apical ligament of dens • Fat pad • Superior longitudinal band of cruciate ligament • Loose connective tissue • Tectorial membrane • Epidural space • Spinal dura mater The ligaments, especially the transverse ligament, are an important factor for maintaining stability in the atlantoaxial joints. Other factors are the joint capsules and the suboccipital muscles. At the level of the atlas the transverse ligament divides the vertebral canal into two parts: the anterior third, which contains the dens, and the posterior two thirds, which contains the spinal cord and surrounding meninges. The cord itself occupies half of the posterior two

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Chapter 1 thirds, leaving much space around it. This is necessary to enable uncomplicated rotation of the head. Because the axis of rotation, the dens, is eccentrically located, the consequence of rotation is that the area of the vertebral canal decreases. Abundant space around the spinal cord prevents compression of the cord. Much of the space around the cord is occupied by the internal vertebral venous plexus. This is a massive venous system in the epidural space, which runs downward from the marginal sinus and has connections with numerous veins around the vertebral column as far as the pelvic cavity. It has been radiologically demonstrated that during atlantoaxial rotation displacement of blood from this venous plexus takes place at the level of the upper cervical spine, thereby preventing compression of the dural sac. When the neutral position of the head is restored, the plexus fills again. The internal vertebral venous plexus seems to act as a volume buffer in this area.2

Suboccipital Region The suboccipital region is a deep muscle compartment in the superior posterior cervical region. It lies deep to the trapezius, sternocleidomastoid, splenius capitis, and semispinalis muscles. It is inferior to the external occipital protuberance and includes the posterior aspects of the atlas and the axis. In a posterior approach, the final muscle, which has to be removed to enter the region, is the semispinalis capitis. Its main contents are the four suboccipital muscles, the vertebral artery, and the dorsal rami of the upper three cervical spinal nerves. The suboccipital muscles are four short muscles that connect the occipital bone, the atlas,

and the axis. They are named the rectus capitis posterior major, rectus capitis posterior minor, obliquus capitis superior, and obliquus capitis inferior (Table 1.2 and Fig. 1.3). The obliquus capitis inferior is the only one without an attachment to the occipital bone. These muscles extend and rotate the head and are of great importance for posture. They have a high density of muscle spindles, which are sensors of proprioception. It has been stated that the rectus muscles and obliquus capitis superior may be more important as postural muscles than as prime movers. The rectus capitis posterior major and the obliquus capitis muscles form the boundaries of the suboccipital triangle (Fig. 1.4). The floor of this triangle is formed by the posterior atlanto-occipital membrane and the posterior arch of the atlas. Here the vertebral artery is found, lying in a groove on the posterior arch and passing underneath the posterior atlanto-­ occipital membrane on its way to the vertebral canal. The suboccipital nerve, which is the dorsal ramus of spinal nerve C1, emerges between the vertebral artery and the posterior arch. It supplies all four suboccipital muscles and also sends a branch to the semispinalis capitis. There is no intervertebral foramen between the atlas and the axis. Spinal nerve C2 emerges between the posterior arch of the atlas and the lamina of the axis, below the obliquus capitis inferior. Its dorsal ramus, larger than all other cervical dorsal rami, divides into a large medial branch and a small lateral branch. The medial branch is called the greater occipital nerve (Fig. 1.4). It ascends dorsal to the obliquus capitis inferior and pierces the semispinalis capitis while supplying it. It then pierces the trapezius and supplies the skin of the scalp as far forward

Table 1.2  The Suboccipital Muscles Muscle

Origin

Insertion

Rectus capitis posterior major Rectus capitis posterior minor

Inferior nuchal line of occipital bone Inferior nuchal line of occipital bone

Obliquus capitis superior

Spinous process of C2 Posterior tubercle of posterior arch of C1 Transverse process of C1

Obliquus capitis inferior

Spinous process of C2

Occipital bone above inferior nuchal lie Transverse process of C1



Anatomy of the Cervical Spine

Fig. 1.4  Dorsal view of the suboccipital region after removal of the superficial muscles. The dorsal branches of the cervical spinal nerves give rise to the suboccipital (C1), greater occipital (C2), and

third occipital (C3) nerves. The vertebral artery occupies a groove on the posterior arch of C1 and pierces the posterior atlanto-occipital membrane.

as the vertex. The smaller lateral branch supplies the semispinalis capitis, splenius capitis, and longissimus capitis. The dorsal ramus of spinal nerve C3 turns backward after emerging from the intervertebral foramen. It runs dorsal to vertebra C3 and divides into medial and lateral branches. The medial branch gives rise to the third occipital nerve, which ascends next to the midline and pierces the trapezius to supply the skin of the lower occipital and suboccipital regions, medial to the greater occipital nerve (Fig. 1.4). All dorsal rami mentioned here have interconnecting branches.

The vertebral artery may be described in four parts. The first two (prevertebral and cervical) parts are discussed below (see Subaxial Cervical Spine). Having passed through the transverse foramen of C2, it turns laterally to reach the transverse foramen of C1. Then, as the atlantic (third) part, it lies medial to the rectus capitis lateralis, runs in a medial direction ­behind the lateral mass of C1 and deep to the obliquus capitis superior, occupies the groove on the superior surface of the posterior arch of C1 covered by the semispinalis capitis, and enters the vertebral canal below the posterior

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Chapter 1 atlanto-occipital membrane (Fig. 1.4). The intracranial (fourth) part pierces the dura and the arachnoidea mater, enters the cranial cavity through the foramen magnum, and unites with its fellow to form the basilar artery. Usually there is some tortuosity in the artery in its course between the transverse foramina of C2 and C1. This may provide slack, which is necessary to rotate the head without compromising the artery.3 Another artery that should be mentioned here is the occipital artery. This large and tortuous artery is a posterior branch of the external carotid artery. It runs on a groove on the medial side of the mastoid process and continues its course posterior to the obliquus capitis superior and semispinalis. It pierces the fascia, which connects the cranial attachments of the sternocleidomastoid and trapezius; this is the investing layer of the cervical fascia. Tortuous branches supply the scalp as far forward as the vertex. The suboccipital region contains a venous plexus, which receives tributaries from, among others, the external vertebral venous plexus and neighboring muscles. The suboccipital venous plexus drains via the left and right posterior jugular veins, which join the external jugular veins. Although they are not in the suboccipital region, two other short muscles should be mentioned here because they also connect the atlas to the occipital bone. The rectus capitis lateralis arises from the transverse process of C1, and the rectus capitis anterior arises from the anterior surface of the lateral mass of C1. The latter muscle flexes the head in the atlanto-occipital joint, and the rectus capitis lateralis flexes the head laterally.

■■ Subaxial Cervical Spine Joints From C2 downward, the vertebrae articulate via facet joints (zygapophysial joints) and intervertebral disks. At the level of C3 to C7, small uncovertebral joints are present as well.

Facet joints are plane synovial joints between the inferior and superior articular processes of adjacent vertebrae. In the cervical region the articular surfaces are oblique in such a way that they run from superoanterior to inferoposterior. Thus, the inferior facet is directed inferoanteriorly and the superior facet is directed superoposteriorly. The cervical facet joints allow free flexion and extension. They also allow lateral flexion and rotation, which are always coupled due to the oblique joint surfaces. The joint capsules are thin and loose, permitting a wide range of movement. The cervical intervertebral disks are thick in comparison to the height of the vertebral bodies. They are thicker anteriorly, which contributes to the cervical lordosis. They consist of a well-developed nucleus pulposus and an anulus fibrosus. The latter is strikingly different from its fellows in other regions. It has been demonstrated that the adult cervical anulus fibrosus is usually incomplete posteriorly. Instead of concentric laminae it forms a crescentic mass anterior to the nucleus, tapering laterally toward the uncinate processes. Posteriorly it consists of only a thin layer of vertically oriented fibers. The deficiency is reinforced by the posterior longitudinal ligament.4 Usually after the age of 10 fissures develop in the lateral parts of the intervertebral disks. These fissures give rise to the so-called uncovertebral joints or clefts (of Luschka) between the uncinate processes of vertebrae C3 to C7 and the corresponding inferolateral surfaces of the vertebral bodies superior to them. These articulations are unique to the cervical spine. The fissures and thus the joints develop in the upper three disks first and later in the remaining two disks. The joint surfaces are covered with cartilage, and laterally the joints are bounded by connective tissue, which is considered a pseudocapsule. The uncovertebral joints develop from rudimentary articulations into mature joints, which contribute to mobility and stability and may become degenerated with age.5

Muscles The muscles posterior to the cervical spine were discussed above (see General Features). Most

of the anterior and lateral vertebral muscles remain to be discussed. The anterior vertebral muscles are the rectus capitis anterior (see Occiput and Upper Cervical Spine, above), the longus capitis, and the longus colli. The longus capitis runs from the basilar part of the occipital bone to the transverse processes of C3 to C6. The several parts of the longus colli run between the bodies and transverse processes of C1 to C6 and C3 to T1. The longus colli and longus capitis are immediately behind the prevertebral layer of the deep cervical fascia. They flex the head and the neck and are supplied by branches of the cervical spinal nerves. The lateral vertebral muscles are the rectus capitis lateralis (see Occiput and Upper Cervical Spine, above), the levator scapulae, and the scalenus anterior, medius, and posterior. The levator scapulae arises from the transverse processes of C1 to C4 and runs to the superior part of the medial border of the scapula. It acts on the scapula. If the shoulder is fixed, it assists in lateral flexion of the cervical spine. The muscle is supplied by the dorsal scapular nerve and additional branches of the cervical plexus. The scalenus muscles have their origins on the transverse processes—the scalenus anterior on C3 to C6, the scalenus medius on C3 to C7, and the scalenus posterior on C4 to C6—and run to the first rib (scalenus anterior and scalenus medius) or the second rib (scalenus posterior). The scalenus muscles may act on the cervical spine (lateral flexion, and if both anterior scalenus muscles work together they flex the spine) or the ribs (elevation during forced inspiration). The scalenus muscles are supplied by short branches of the cervical spinal nerves.

Topographical Relationships A good understanding of the position of the cervical spine and its major topographical relationships can be obtained by studying transverse sections of the neck (Fig. 1.5). The neck has a system of fascias, which, through their disposition, create compartments. The clinical significance of compartments is that they determine and limit the spread of pathology, especially infection, to a certain extent.

Anatomy of the Cervical Spine The superficial cervical fascia is the subcutaneous connective tissue, which connects the dermis to the deep fascia. It contains a variable amount of fat, and anterolaterally it contains the platysma. The deep cervical fascia consists of three layers: investing (or superficial), pretracheal, and prevertebral. It also forms the carotid sheath. The well-visible investing layer surrounds the neck like a collar and splits to enclose the sternocleidomastoid and trapezius. Posteriorly it is connected to the periosteum of spinous process C7 and to the nuchal ligament. The pretracheal layer is thin and present only in the anterior part of the neck. Two parts are distinguished. One part encloses the infrahyoid muscles or strap muscles and is fused with the investing layer anteriorly. The second part forms an envelope for the thyroid gland. The prevertebral layer surrounds the cervical spine including the pre- and postvertebral muscles. Therefore, the term prevertebral is rather unfortunate, and perivertebral would have been more appropriate. However, it has to be mentioned that the fascia becomes very thin laterally and posteriorly, where it is under the cover of the trapezius. Anteriorly it is quite prominent and divides to form two layers, of which the anterior layer has received its own name, the alar fascia. All three layers of the deep fascia connect to the carotid sheath. This is a condensation of the deep fascia around the common and internal carotid arteries, the internal jugular vein, and the vagus nerve. The disposition of the components of the deep cervical fascia creates muscular, visceral, and neurovascular compartments. The muscular compartments are the spaces occupied by the sternocleidomastoid, infrahyoid, trapezius, and pre- and postvertebral muscles. The visceral compartment lies anteriorly in the neck and contains the thyroid and parathyroid glands, the larynx, the pharynx, and the upper parts of the trachea and the esophagus. Posteriorly it is closed by a visceral fascia. Behind the pharynx is the buccopharyngeal fascia, which continues downward into the esophageal adventitia. The neurovascular compartment is the space inside the carotid sheath. Special attention has to be paid to two interfascial spaces that mainly contain loose connective tissue. They are the

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Chapter 1

Fig. 1.5  Transverse section of the neck at the level of vertebra C5. The deep cervical fascia has investing, pretracheal, and prevertebral layers, and also forms the carotid sheath. Their disposition

results in muscular, neurovascular, and visceral compartments. In an anterior approach the cervical spine can be reached between the visceral and neurovascular compartments.

slit-like spaces between the visceral fascia and the alar fascia, and between the alar fascia and the prevertebral layer proper. These spaces allow movement of the viscera relative to the cervical spine during swallowing. The anterior space is termed the retrovisceral space and consists of retropharyngeal and retroesophageal parts. The posterior space has received the name “danger space,” which illustrates the clinical significance of these spaces. Because both spaces continue downward into the mediastinum, they form important routes for the spread of infections from the head and neck region to the mediastinum. From the transverse section it can be understood that an anterior approach of the cervical spine may go between the neurovascular and visceral compartments (Fig. 1.5). When it is

performed carefully, important structures are avoided. Tiny branches of the ansa cervicalis are at risk, however. The ansa cervicalis is a neural loop of the cervical plexus that is embedded in the carotid sheath. Its branches supply the infrahyoid muscles. Another structure to keep in mind, and functionally more important, is the sympathetic trunk. It is embedded in the prevertebral layer of the deep cervical fascia, posteromedial to the carotid sheath and at the level of the transverse processes of the vertebrae. The lower half of the cervical part of the sympathetic trunk may consist of several strands, which makes it more difficult to identify. Superiorly it forms a single bundle. Here it contains the elongated superior cervical ganglion, which lies on the transverse processes of C2 and C3.

The cervical plexus is formed by ventral rami of spinal nerves C1 to C4. It is anteromedial to the levator scapulae and scalenus medius. Its cutaneous branches supply the anterior and lateral parts of the neck. An important motor branch is the phrenic nerve, which runs down on the anterior surface of scalenus anterior. In the lower part of the neck the recurrent laryngeal nerve ascends on its way to the larynx. Traditionally described as lying in the groove between the trachea and esophagus, this is generally the case only just below its entrance into the larynx. Further down it is embedded in the loose connective tissue next to the trachea and the esophagus, more often paratracheally than paraesophageally.6 The vertebral artery comes from the first part of the subclavian artery. Its first part, the prevertebral part, ascends between the longus colli and scalenus anterior. It lies anterior to the transverse process of C7 and ventral rami of cervical nerves C7 and C8. It enters the transverse foramen of C6 and from here is called the vertebral (second) part. It ascends through the transverse foramina of the remaining vertebrae and is surrounded by a plexus of veins, which low in the neck forms the vertebral vein that joins the brachiocephalic vein. The vertebral artery may start its course through the transverse foramina on a different level, even as high as C3. Between the transverse processes the artery lies anterior to the ventral rami of spinal nerves C2 to C6. The third and fourth (atlantal and intracranial) parts were discussed above (see Occiput and Upper Cervical Spine).

■■ Chapter Summary The cervical spine is the most mobile part of the vertebral column, permitting flexion and extension, lateral flexion, and rotation. It consists of seven relatively small vertebrae, of which the presence of a transverse foramen for passage of the vertebral artery is a distinctive feature. The atlas and the axis are atypical vertebrae. The atlanto-occipital joints are important for the movement of nodding the head, whereas

Anatomy of the Cervical Spine the atlantoaxial joints permit a rotation of about 40 degrees. Stability in these craniovertebral joints, with their wide range of movement, comes from joint capsules, membranes, ligaments, and the suboccipital muscles. Especially the strong transverse ligament of the atlas should be mentioned as well as the suboccipital muscles, which are very important for posture and have a high density of muscle spindles. These muscles lie in the suboccipital region, deep to the semispinalis capitis. They have a close topographical relationship with the vertebral artery, the suboccipital nerve that supplies these muscles, and the greater occipital nerve. From C2 downward, the cervical vertebrae articulate via obliquely positioned facet joints and relatively thick intervertebral disks. The adult anulus fibrosus of the disks is usually ­incomplete posteriorly. This deficiency is reinforced by the posterior longitudinal ligament. At the level of C3 to C7 small uncovertebral joints develop in the lateral parts of the intervertebral disks after the age of 10. These joints contribute to mobility and stability. The posterior relationships of the cervical spine include the nuchal ligament and the dorsal muscles. The nuchal ligament is a bilaminar intermuscular septum that provides attachment for muscles. Easy access to the vertebrae is obtained between the layers of the ligament. The dorsal muscles form a greater muscle mass than the prevertebral muscles because most body weight is anterior to the spine. They are divided into superficial, intermediate, and deep groups, of which only the deep muscles are true intrinsic back muscles. They have a multilayered arrangement and are divided into the splenius muscles, erector spinae components, and the transversospinalis group. The latter group includes the semispinalis capitis, which is visible as a longitudinal bulge next to the midline. Important anterior relationships include the viscera of the neck, the structures inside the carotid sheath, the cervical plexus, the sympathetic trunk, and the recurrent laryngeal nerve. An anterior approach to the cervical spine may go between the visceral and neurovascular compartments.

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Chapter 1 Pearls

Pitfalls

◆◆ Recognize that the cervical spine is the most mo-

◆◆ Do not overlook the factors that maintain stabil-

◆◆

◆◆ Do not overlook the precise course of the verte-

◆◆ ◆◆ ◆◆ ◆◆

bile part of the vertebral column. Recognize the distinctive features of the cervical  vertebrae, including those of the atypical vertebrae. Be aware of the multilayered arrangement of the intrinsic back muscles. Recognize the wide range of movement of the craniovertebral joints. Understand the importance of the suboccipital muscles as postural muscles. Understand the disposition of the components of  the deep cervical fascia and the creation of compartments.

ity in the craniovertebral joints.

bral artery and the nerves in the suboccipital region. ◆◆ Do not overlook the course of the neural structures anterior to the cervical spine.

References

Five Must-Read References 1. Duray SM, Morter HB, Smith FJ. Morphological variation in cervical spinous processes: potential applications in the forensic identification of race from the skeleton. J Forensic Sci 1999;44:937–944 PubMed  2. Reesink EM, Wilmink JT, Kingma H, Lataster LM, van Mameren H. The internal vertebral venous plexus prevents compression of the dural sac during atlanto-axial rotation. Neuroradiology 2001;43:851– 858 PubMed  3. Wiseman O, Logan B, Dixon A, Ellis H. Tortuosity in the cervical part of the vertebral artery. Clin Anat 1994;7:26–33

 4. Mercer S, Bogduk N. The ligaments and annulus fibrosus of human adult cervical intervertebral discs. Spine 1999;24:619–626, discussion 627–628 PubMed  5. Hartman J. Anatomy and clinical significance of the uncinate process and uncovertebral joint: a comprehensive review. Clin Anat 2014;27:431–440 PubMed  6. Liebermann-Meffert DM, Walbrun B, Hiebert CA, Siewert JR. Recurrent and superior laryngeal nerves: a new look with implications for the esophageal surgeon. Ann Thorac Surg 1999;67:217–223 PubMed

2 Biomechanics of the Cervical Spine: From the Normal State to the Injury State Ahmer K. Ghori, Dana Leonard, and Thomas Cha

■■ Introduction Cervical spine injuries are commonplace and generally occur in a bimodal distribution: young patients in the setting of high-energy trauma and elderly patients in the setting of low-energy falls. Cervical trauma can be categorized into specific injury patterns resulting from characteristic mechanisms, most commonly involving compression, flexion/extension, or rotational force vectors. To understand the injury state, one needs to first understand the anatomy of the cervical spine, including the numerous, varied structures that stabilize it, and the biomechanics that allow for its physiological range of motion. This chapter describes the relationship between the biomechanics of the cervical spine and cervical trauma, and reviews the recognizable injury patterns that can occur when stabilizing structures in the cervical spine are disrupted by specific force vectors. Although attributing specific force vectors to injury patterns is a simplification of actual trauma, it enables a greater understanding of cervical trauma in the setting of normal biomechanics.

■■ Biomechanics: Functional

Anatomy and Stability

Understanding cervical anatomy is crucial to understanding cervical biomechanics. The cer-

vical spine consists of seven vertebrae aligned on average in 20 to 40 degrees of lordosis. The functional anatomy of the cervical spine can be divided into upper and lower cervical spine, each with its unique features. A complex set of osseous and ligamentous structures maintains the stability of the cervical spine within the range of physiological motion, allowing the spine to support the head at the occipitocer­ vical junction; to flex, extend, and rotate; to articulate with the body at the cervicothoracic junction; and to protect the spinal cord, vertebral artery, and nerves.1

Functional Anatomy: Upper Cervical Spine The upper cervical spine is composed of the C1 vertebra, C2 vertebra, and their respective articulations: the occipitocervical joint and the atlantoaxial joint. A complex set of ligaments stabilizes the upper cervical spine and facilitates physiological motion.

C1 Vertebra The C1 vertebra, also called the atlas, is the only purely ring structure in the cervical spine. It is composed of an anterior and posterior arch linked on either side by relatively large lateral masses. It has concave superior articular facets that articulate with the convex occipital condyles; this convex-on-concave articulation



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Chapter 2 enables flexion-extension at the occipitocervical joint.2 The inferior facets of C1 are convex and articulate with the convex superior facets of C2; this convex-on-convex articulation enables rotation at the C1-C2 joint.

C2 Vertebra The C2 vertebra, also called the axis, is a transitional segment with both unique morphometric features and shared elements with the subaxial cervical spine. Anteriorly it has an odontoid process that articulates with the anterior arch of C1. The superior and inferior facets are offset in the sagittal plane, with the superior facet being more anterior than the inferior facet. This offset gives rise to an elongated pars articularis that is oriented approximately 45 degrees in the sagittal plane. This sagittal offset places disproportionately high stress on the C2 pars, giving rise to the potential for injury and instability, as discussed later in this chapter.

Occipitocervical Joint The occipitocervical (OC) joint is devoid of a disk; therefore, stability is derived from the ball-and-socket joint formed by the convex occipital condyles articulating with the concave C1 superior facets. This joint is the only weight-bearing articulation between the head and the spine and is supported by a thick joint. Motion in the OC joint is predominantly nutational (nodding) and, within the physiological range of 50 degrees of motion, does not result in anterior to posterior translation due to conformity of the atlantal socket and strong stabilizing restraint from the tectorial membrane, which is the cranial continuation of the posterior longitudinal ligament (PLL) The cranial continuation of the anterior longitudinal ligament (ALL) also stabilizes this joint, but to a lesser extent. The alar ligaments, which originate on the odontoid and insert on each occipital condyle, are the primary restraint to axial rotation in the upper cervical spine.3,4

Atlantoaxial Joint Both the inferior facets of C1 and the superior facets of C2 are convex, which enables the pre-

dominantly rotational motion in the atlantoaxial joint; 50 degrees of rotation is normal. As the atlas rotates around the odontoid, the ipsilateral lateral mass slides backward and medially while the contralateral lateral slides forward and medially.5 The primary stabilizer for posterior displacement of the atlas is the odontoid process, whereas anterior displacement is resisted by the transverse atlantal ligament,6 with secondary contributions from the C1–C2 joint capsule, and the apical ligament. The primary stabilizers to axial rotation at C1–C2 include the alar ligaments (attaching the skull to the odontoid process) and joint capsule. Extrinsic stabilizers include the paraspinal muscles, the ligamentum nuchae, and the interspinous ligaments.

Functional Anatomy: Subaxial Spine The C3 through C7 vertebrae have similar morphology and stabilizing ligamentous structures and are discussed together as the typical cervical vertebrae. There are three main anatomic structures that contribute to stabilization of the vertebrae in the subaxial cervical spine: the uncinate process, the facet joints, and the circumferential ligamentous buttress of ALL and PLL. The uncinate process, which is a bony projection on the dorsolateral-superior aspect of each vertebral body, articulates with the inferior aspect of the cranial vertebral body. Conceptually, one can consider them to be organized in a stacked flower-pot fashion. The uncovertebral articulation adds stability to the cervical spine by limiting lateral bending.7 The facet joints in the subaxial cervical spine are oriented 45 degrees below horizontal in the sagittal plane. This orientation enables flexion-­ extension of the subaxial cervical spine, which generates 50% of cervical flexion-extension. The facets also mainly resist axial compression forces, typically absorbing 20 to 30% of compressive loads8 while also providing resistance to hyperflexion and shear forces. The circumferential ligamentous buttress is created by the ALL, PLL, and interspinous ligaments.2 These ligaments stabilize the spine by



Biomechanics of the Cervical Spine

preventing motion beyond the physiological range.

Functional Stability The normal cervical spine is able to withstand physiological loads, maintain a normal posture, and protect neural elements without pain. Specific stabilizing mechanisms in response to three types of forces are discussed here.

Compression The structures that bear compressive forces are the vertebral column and disks. The vertebral end plates tend to fail before the disks when supranormal compressive forces are applied.9,10

Flexion and Extension Flexion forces are neutralized by the paraspinal muscles, supraspinous ligament, interspinous ligament, facet joint/capsule complex, and ligamentum flavum. Cadaveric studies have shown that flexion instability correlates best with injury to the interspinous/supraspinous ligaments, and ligamentum flavum, whereas extension instability correlates best with disruption of the ALL, disruption of the disk’s end plate, and capsular injuries.11,12

Rotation In the upper cervical spine, the alar ligaments are the primary rotatory restraint, with contri-

butions from the OC joint capsule, tectorial membrane, and transverse ligament. In the subaxial spine, the intervertebral disk, facet joints/ capsule, and posterior ligamentous complex all serve as rotatory restraints.

■■ Biomechanics: Defining

Instability

The complex biomechanics of the cervical spine make it difficult to have a unifying system that characterizes instability. White and Panjabi13 described the physiological motion in a normal cervical spine (Table 2.1), and defined stability as the “ability of the spine under physiologic loads to limit patterns of displacement so as not to damage or irritate the spinal cord or nerve roots and, in addition, to prevent incapacitating deformity or pain due to structural changes.” In the occipitocervical junction, instability is suggested when axial rotation on one side is greater than 8 degrees and there is more than 1 mm of translation between the basion and the odontoid with flexion/extension. At the atlantoaxial junction, instability is suggested when there is a combined lateral overhang of C1 on C2 in excess of 7 mm, unilateral rotation of C1-C2 of more than 45 degrees, an atlanto– dens interval (ADI) greater than 3 mm, and space available for the cord (SAC) less than 13 mm.14 In the subaxial cervical spine, instability is suggested with translation in the sagittal plane

Table 2.1  Normal Motion of the Cervical Spine (in Degrees) Segment C0-C1 C1-C2 C2-C3 C3-C4 C4-C5 C6-C7 C7-T1

Flexion/Extension

Lateral Bending

Rotation

25 20 10 15 20 17  9

 5  5 10 11 11  7  4

 5 40  3  7  7  6  2

Source: Adapted from White AA, Panjabi MM. Clinical Biomechanics of the Spine, 2nd ed. Philadelphia: Lippincott; 1990.

19



20

Chapter 2 greater than 3.5 mm or 20% on flexion/extension radiographs, or sagittal plane angulation more than 11 degrees on resting lateral radiographs. Other factors that suggest instability include disruption of anterior or posterior columns, spinal cord or nerve root injury, congenital cervical stenosis (SAC < 13 mm), and abnormal disk space narrowing.2 Determining instability in the case of ligament injury can be particularly challenging. Cadaveric studies have shown that throughout the cervical spine, structural integrity is maintained as the supraspinous/interspinous ligaments are transected, but becomes unstable as the PLL is transected.14 Therefore, it is important to identify posterior ligamentous integrity when evaluating the stability of the traumatic cervical spine. Traditionally, flexion/extension and open-mouth radiographs were used to help identify ligamentous injury, but magnetic resonance imaging (MRI) has now replaced these modalities, as it is far more sensitive and specific. Furthermore, MRI is safer than dynamic imaging in the acute setting.

■■ Biomechanics: The Injured

Cervical Spine

By differentiating the types of force vectors, cervical trauma can be categorized into specific injury patterns that can be understood based on the biomechanics of the cervical spine. Although this organizational approach is a simplification, as most spine trauma is the result of a complex and unpredictable force vectors, it helps explain trauma in the context of normal biomechanics.

Flexion Injuries Flexion injuries are the result of rapid acceleration or deceleration of the spine as the torso stays in place while the head keeps moving. With hyperflexion, the anterior elements fail under compression while the posterior elements experience tensile failure. Depending on the position of the axis of rotation, flexion injuries can result in flexion-compression or

flexion-distraction injury patterns. The spectrum of injury can range from a sprain to gross instability, with neurologic compromise depending on the amount of energy imparted in the trauma. The posterior ligamentous structures progressively fail under tension, starting with the supraspinous ligament, then the interspinous ligament and the ligamentum flavum, and finally the PLL. Plain radiographs can be deceivingly benign, as ligamentous structures are not visualized and one must rely on subtle secondary markers of instability such as interspinous widening, local kyphosis, and disk space widening. Flexion/extension imaging should be avoided in the setting of traumatic flexion injuries as it can exacerbate an already unstable spine. MRI is the imaging modality of choice to characterize the injury pattern, as it is highly sensitive and specific, and helps in guiding treatment. Several types of injuries can be seen with a flexion force, and the main ones are summarized in the following subsections.

Clay-Shoveler’s Fracture This is an avulsion process of the spinous process, typically at C7.15 It results when a flexion moment overcomes the tension band effect of the interspinous ligaments, leading to bony failure at the tip of the spinous process.

Posterior Ligamentous Injury A flexion moment can lead to pure ligament injury on a scale from minor neck sprain to complete disruption of posterior ligamentous structures. In purely ligamentous injury, initial radiographs may show normal alignment. The only suggestion of injury may be subtle in­ terspinous widening, end-plate angulation, or local kyphosis. In some cases the ligamentous injury can progress if the posterior tension band is unable to tolerate physiological loading. Some literature demonstrates a 30 to 50% incidence of delayed instability.16 Therefore, an MRI should be obtained to rule out posterior ligamentous injury if it is suspected from the mechanism of injury, the examination (posterior neck pain), or subtle findings on plain radiographs.17



Simple Wedge Compression Fractures The flexion moment causes anterior vertebral bodies impingement, which can wedge the disk through the end plate.18 This gives rise to a compression fracture with central disk depression. Typically the posterior elements are intact; however, a posterior ligamentous injury cannot be excluded based on static radiographs.

Flexion-Compression (Teardrop Fracture) In this pattern of injury the posterior elements fail under tension and the axis of rotation lies within the vertebral body, giving rise to the anterior-inferior vertebral body fracture. Depending on the amount of force, this injury may be stable or unstable. In lower energy mechanisms, the PLL remains intact, the anterior and posterior spinal columns maintain their alignment, and the only suggestion of pathology may be the bony injury and subtle interspinous widening. With more energy, the posterior inferior vertebral body may sublux into the canal, and the most severe form of this injury occurs when the PLL is torn, leading to significant fragment retropulsion and likely neural injury.2

Flexion-Distraction Injury In this injury pattern, there is a flexion moment and the axis of rotation is anterior to the vertebral body. The spectrum of injury ranges from posterior element sprain to complete posterior element and disk space disruption, resulting in anterior posterior column instability. In early injury stages, bilateral facet subluxation may result from the flexion distraction force.2 With more force, the injury may progress to bilateral “perched” face, as the inferior articular facet is displaced superior and anterior to the superior articular facet. The most severe instance of an injury caused by a flexion-­ distraction force is a bilateral facet dislocation, wherein the inferior articular processes lie anterior to the superior articular process. This injury is often associated with a tensile failure of the disk space and fractures of the lateral mass, pedicle, lamina, or spinous process. In 50

Biomechanics of the Cervical Spine to 60% of cases the vertebral artery is injured as well.19 Excess of 50% anterior translation of the superior vertebra, which can typically be seen on lateral radiographs, may suggest a high likelihood of neurologic injury.2

Flexion-Translation Injury A flexion-translation vector force on the cervical spine leads to bilateral facet injuries. The injury pattern may be pure superior articular process fractures, pure inferior articular process fractures, or a combination of both.20 Unlike facet dislocations, facet fractures are not associated with capsular disruption. The posterior ligamentous complex may be stretched but is not disrupted. However, if the flexion-­ translation force is coupled with tensile force, then the posterior ligamentous complex may be torn and associated tensile fracture, such as laminar or pedicle fractures, can also occur.21 If there is a shear component to the force, it may also disrupt the posterior ligaments and progress to disk disruption as well.2

Flexion-Rotation Injury Flexion moment combined with a rotational torque can lead to either unilateral facet fracture or unilateral facet dislocation. Superior facet fractures are more common than inferior facet fractures.22 With dislocation, the facet capsule is disrupted, but with facet fracture the capsule remains intact. However, the intact capsule may recoil the fractured fragment into the neural foramen, causing neurologic symptoms. Unilateral facet dislocations can be associated with translation of the cranial vertebrae, but this is limited to 25% if the injury is truly unilateral.2

Flexion-Lateral Bending Uncinate process fractures result from a pure flexion-lateral bending force on the cervical spine.23 However, cervical spine motion is coupled such that lateral bending usually causes rotation; thus, pure flexion-lateral bending injuries are exceedingly rare.2

21



22

Chapter 2

Flexion Injuries of the Upper Cervical Spine Severe flexion injury with horizontal sheer or distraction can disrupt the ligamentous structures stabilizing the occipitocervical junction and lead to an anterior occipitocervical dis­ location. This is often a fatal injury, and even when not fatal it is often missed during initial trauma evaluation. Therefore, every cervical spine computed tomography (CT) scan should include the occipitocervical junction, and the treating surgeon must pay close attention to rule out this injury using lateral radiographs and the CT scan.

Extension Injuries Extension injuries typically are the result of rapid acceleration or deceleration when the head stops and the body keeps moving, or a fall in older individuals with frontal head strike. With hyperextension the posterior elements fail under compression, whereas anterior elements experience tensile failure. The injury spectrum may begin with an ALL tear. Additional tensile or sheer force may lead to disruption of the disk space or compressive fractures of the lamina, facets, or spinous process. The terminal end of this injury spectrum is posterior translation of the vertebral body leading to cord compression. In cases of pure ligamentous injury, initial injury plain radiographs may be deceivingly reassuring, as the only marker of injury might be a slightly fish-mouthed anterior disk space. In cases of bilateral facet fractures, there may be a disk space injury, which makes the overall pattern unstable and may only be detectable with a MRI. The treating surgeon must maintain a high level of suspicion for these injuries, particularly in patients with congenital stenosis/degenerative spondylosis or in patients with a fused cervical spine such as those with ankylosing spondylitis or diffuse idiopathic skeletal hyperostosis (DISH). Patients with congenital stenosis are more likely to experience neurologic deficits from direct compression, or incomplete cord injury such as central cord syndrome. In patients with fused cervical spines, hyperextension injury can result in an injury similar to a long bone frac-

ture, resulting in gross instability at the injury level.24 Patients with ankylosing spondylitis are also at higher risk for excessive bleeding from the disk space injury, which can result in progressive neurologic decline.25

Lateral Mass Fracture-Separation Extension-rotation leads to a lateral mass fracture-separation; this is defined as an ipsilateral pedicle and lamina fracture leading to a floating lateral mass. Depending on the energy imparted, the lateral mass may be dislocated, which would lead to instability at the superior and inferior levels. The majority of instability occurs at the level of injury or level inferior to the injury.26

Hyperextension Injuries of Upper Cervical Spine Hyperextension leads to a compressive force on the posterior arch of C1, as it is impinged between the occiput and posterior elements of C2. A pure hyperextension injury would lead to just a posterior arch fracture of C2. If the extension is coupled with axial load, then a bilateral anterior and posterior arch fracture (Jefferson fracture) may be seen.27 This injury places tensile strain on the transverse ligament, and can lead to a midsubstance tear of the transverse ligament or an avulsion fracture off the lateral mass. This can be an unstable injury pattern, and a combined lateral mass overhang of more than 7 mm suggests an unstable biomechanical situation. Tensile force on the anterior C1 may lead to an anterior avulsion fracture of C1, where the ALL and longus colli insert. The hyperextension force may be combined with other forces such as lateral bending, axial load, and rotation. These combined force vectors may result in any combination of C1 anterior arch, posterior arch, lateral lass, or transverse process fractures.

Axis Fractures Axial load coupled with hyperextension leads to a shear stress on the pars interarticularis of C2.2 This can lead to bilateral C2 pars fracture, also known as a hangman’s fracture. After the initial injury, flexion or distraction moments may

lead to any combination of distraction and displacement, which can lead to neurologic injury. Hyperextension injury coupled with severe sheer or distraction can lead to a posterior ­atlanto-occipital dislocation. As discussed earlier, the treating surgeon must pay close attention to rule out this injury in the trauma setting.

Atlantoaxial Subluxation and Dislocation Disruption of the stabilizing ligaments around the C1-C2 joint can lead to several different injury patterns that result in subluxation or dislocation of the atlantoaxial joint. With hyperflexion, the transverse ligament serves as the restraint to anterior displacement of C1.2 If this is torn or if the odontoid fractures below the ligament, then the atlas subluxates an­ teriorly and with enough force an anterior ­atlantoaxial dislocation may be seen. With a hyperextension force, a posteriorly displaced odontoid fracture may result, with a posterior atlantoaxial subluxation or dislocation.2 Rotatory stability of the atlantoaxial joint comes primarily from the alar ligaments, with secondary contribution from the transverse ligament, tectorial membrane, and facet capsules. With enough rotatory torque these structures can fail, leading to rotatory subluxation or dislocation.28

Biomechanics of the Cervical Spine cal spine through the physiological range of motion is important in recognizing the injuries that can result from the application of specific force vectors and the failure of one or more of those stabilizing structures. Depending on the extent of injury, the cervical spine may not be able to support the head or tolerate physiological loads while still protecting the spinal cord. Initial radiographs can be deceptively benign because severe ligamentous injury may not be detected on plain X-rays if the overall alignment is maintained. MRI plays a large role in identifying ligamentous instability and has become an integral part of evaluating cervical trauma. To successfully treat patients, the surgeon must understand the functional anatomy, the role it plays in the biomechanics that maintain the stability of the cervical spine, and how specific force vectors can lead to recognizable injury patterns. Pearls ◆◆ One needs to understand normal cervical anat-

omy and biomechanics, because cervical trauma can be organized into discrete forces that disrupt the normal biomechanics. ◆◆ Upright cervical spine radiographs serve as a useful tool to assess functional (with gravity) stability of osteoligamentous structures. Pitfall ◆◆ Plain radiographs can miss severe ligamentous

■■ Chapter Summary Understanding the anatomic osseoligamentous structures that maintain stability in the cervi-

injury if the overall alignment is maintained. MRI plays a large role in identifying ligamentous instability and has become an integral part of evaluating cervical trauma.

References

Five Must-Read References 1. Voo LM, Pintar FA, Yoganandan N, Liu YK. Static and dynamic bending responses of the human cervical spine. J Biomech Eng 1998;120:693–696 PubMed  2. Savas PE. Biomechanics of the injured cervical spine. In: Vaccaro AR, eds. Fractures of the Cervical, Thoracic, and Lumbar Spine. New York: Marcel Dekker; 2003:23–44 3. Dvorak J, Panjabi MM. Functional anatomy of the alar ligaments. Spine 1987;12:183–189 PubMed

4. Dvorak J, Schneider E, Saldinger P, Rahn B. Bio­ mechanics of the craniocervical region: the alar and transverse ligaments. J Orthop Res 1988;6:452–461 PubMed 5. Bogduk N, Mercer S. Giomechanics of the cervical spine. I: Normal Kinematics. Clin Biomech (Bristol, Avon); 2000;15:633-648. 6. Fielding JW, Cochran Gv, Lawsing JF III, Hohl M. Tears of the transverse ligament of the atlas. A clinical and

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Chapter 2 biomechanical study. J Bone Joint Surg Am 1974;56: 1683–1691 PubMed 7. Clausen JD, Goel VK, Traynelis VC, Scifert J. Uncinate processes and Luschka joints influence the biomechanics of the cervical spine: quantification using a finite element model of the C5-C6 segment. J Orthop Res 1997;15:342–347 PubMed 8. Maiman DJ, Sances A Jr, Myklebust JB, et al. Compression injuries of the cervical spine: a biomechanical analysis. Neurosurgery 1983;13:254–260 PubMed  9. Maiman DJ, Yoganandan N. Biomechanics of cervical spine trauma. Clin Neurosurg 1991;37:543–570 PubMed 10. Brown T, Hanson R, Yorra A. Some mechanical tests on the cervical spine with particular reference to the intervertebral discs. J Bone Joint Surg 1957;39:1135– 1141 PubMed 11. Panjabi MM, White AA III, Johnson RM. Cervical spine mechanics as a function of transection of components. J Biomech 1975;8:327–336 PubMed 12. Panjabi MM, Oxland TR, Parks EH. Quantitative anatomy of cervical spine ligaments. Part II. Middle and lower cervical spine. J Spinal Disord 1991;4:277–285 PubMed 13. White AA, Panjabi MM. Clinical Biomechanics of the Spine, 2nd ed. Philadelphia: Lippincott; 1990 14. White AA III, Panjabi MM. Update on the evaluation of instability of the lower cervical spine. Instr Course Lect 1987;36:513–520 PubMed 15. Cancelmo JJ Jr. Clay shoveler’s fracture. A helpful diagnostic sign. Am J Roentgenol Radium Ther Nucl Med 1972;115:540–543 PubMed 16. Southern EP, Pelker RR, Crisco JJ II, Panjabi MM. Posterior element strength six months postinjury in the canine cervical spine. J Spinal Disord 1993;6:155– 161 PubMed 17. Vaccaro AR, Falatyn SP, Flanders AE, Balderston RA, Northrup BE, Cotler JM. Magnetic resonance evaluation of the intervertebral disc, spinal ligaments, and spinal cord before and after closed traction reduction of cervical spine dislocations. Spine 1999;24:1210– 1217 PubMed

18. Crowell RR, Shea M, Edwards WT, Clothiaux PL, White AA III, Hayes WC. Cervical injuries under flexion and compression loading. J Spinal Disord 1993; 6:175–181 PubMed 19. Willis BK, Greiner F, Orrison WW, Benzel EC. The incidence of vertebral artery injury after midcervical spine fracture or subluxation. Neurosurgery 1994; 34:435–441, discussion 441–442 PubMed 20. Shanmuganathan K, Mirvis SE, Levine AM. Rotational injury of cervical facets: CT analysis of fracture patterns with implications for management and neurologic outcome. AJR Am J Roentgenol 1994;163:1165– 1169 PubMed 21. Yoganandan N, Pintar FA, Maiman DJ, Cusick JF, Sances A Jr, Walsh PR. Human head-neck biomechanics under axial tension. Med Eng Phys 1996;18:289– 294 PubMed 22. Levine AM. Facet injuries in the cervical spine. In: Camins MB, O’Leary PF, eds. Disorders of the Cervical Spine. Baltimore: Williams & Wilkins; 1992:289–302 23. Lee C, Kim KS, Rogers LF. Triangular cervical vertebral body fractures: diagnostic significance. AJR Am J Roentgenol 1982;138:1123–1132 PubMed 24. Kwon BK, Hilibrand AS. Management of Cervical fractures in patients with diffuse idiopathic skeletal hyperostosis. Curr Opin Orthop 2003;14:187–192 25. Kwon BK, Vaccaro AR, Grauer JN, Fisher CG, Dvorak MF. Subaxial cervical spine trauma. J Am Acad Orthop Surg 2006;14:78–89 PubMed 26. Levine AM. Facet fractures and dislocations. In: Levine AM, Eismont FJ, Garfin SR, Zigler JE, eds. Spine Trauma. Philadelphia: WB Saunders; 1998:331–366 27. Jackson RS, Banit DM, Rhyne AL III, Darden BV II. Upper cervical spine injuries. J Am Acad Orthop Surg 2002;10:271–280 PubMed 28. Dvorak J, Panjabi M, Gerber M, Wichmann W. CT-functional diagnostics of the rotatory instability of upper cervical spine. 1. An experimental study on cadavers. Spine 1987;12:197–205 PubMed

3 Evaluation of an Injured Cervical Spine Richard Assaker, Fahed Zairi, and Xavier Demondion

■■ Introduction In adult blunt trauma, cervical spine injuries represent 2 to 6% of cases,1,2 and one third of all spinal injuries.3 Forty-three percent of cervical spine injuries are considered clinically unstable. Approximately 0.2% of these injuries are misdiagnosed and might result in catastrophic neurologic lesions. Evaluation of a trauma patient is critical to “rule out” and “clear” the cervical spine. Rapid discontinuation of cervical immobilization needs to be counterbalanced against the risk of spinal cord injury as consequences of a missed spine injuries. Physicians in general act defensively and ask for a combination of plain radiographs, computed tomography (CT) scans, and magnetic resonance imaging (MRI) for the evaluation of the bony and ligamentous structures of the cervical spine.4,5 On the one hand, a missed cervical spine injury can lead to catastrophic consequences and litigation costs,6,7 but on the other hand many complications may occur if the immobilization of patients by the use of collars continues for more than 72 hours.8 The risk of skin ulcers and sores increases by 66% for each day of additional immobilization.9 To avoid missing cervical spine injuries, clinicians liberally order

advanced imaging studies that, in the majority of the cases, turn out to be normal. This policy increases the health care costs and the unnecessary exposure to ionizing radiations.10,11 A proper evaluation (clinical first) might clear the cervical spine with no need for further investigations such as radiographs or CT scans.12,13 This chapter describes the best current evidence-based cervical spine clearance protocol, and discusses a clinical method to identify patients that does not entail imaging investigations. For patients who do require imaging, this chapter discusses the type of images that are required in alert and obtunded patients.

■■ Clinical Evaluation The goals of the clinical evaluation of a patient who sustained a blunt cervical trauma are to “clear” the cervical spine clinically and to identify patients who require additional radiographic investigations. In an alert patient this first step should be straightforward and easy. In an unconscious patient who is clinically not evaluable, the clearance relies on imaging studies only. Patients with severe head trauma



26

Chapter 3 (low Glasgow Coma Scale [GCS] score) are at high risk of having cervical spine injuries, too. Suspicion of a cervical spine (C-spine) injury must be maintained and the spine immobilized until full clearance is provided by a proper clinical and radiographic workup.

■■ Radiological Assessment Plain Films Three-View Radiographs Standard radiographs are often considered as the initial screening radiographic evaluation in symptomatic or obtunded trauma patient. The three-view protocol is usually the standard exam: anteroposterior, lateral cervical, and odontoid views (Fig. 3.1). In cervical spine trauma, plain films are ­accurate enough to detect 84% of all cervical injuries.14 Limitations are technical due to inadequate exposure of the cervicothoracic junction and the atlantoaxial complex. In an obscured area, oblique views or a CT is recommended before discontinuing cervical immobilization.

Dynamic Views Adding to the three-view radiograph, active flexion extension views in a symptomatic and awake patient with normal plain static films will increase the sensitivity (99%) and specificity (93%). They are usually ordered to exclude suspected diskoligamentous injuries (Fig. 3.2). The value of these views in the acute setting is debatable due to possible false negatives because of muscle spasms. In comatose patients with normal three-view films, passive flexion-extension radiographs are questionable and might be dangerous. Pure

ligamentous injuries are rare (0.4%), and in ­ lmost all cases plain radiographs and CT are a accurate for detecting these injuries. In a series of 14,577 patients with cervical trauma, 2,605 patients were not evaluable and 14 patients had isolated ligamentous injury detected on plain static radiographs or CT.15

Computed Tomography Scan High-quality CT scans surpass radiographs in detecting cervical spine injuries, especially in obtunded patients. The ease of access, the speed of the study, and the sensitivity and specificity of CT makes it the modality of choice in many trauma centers. In addition, CT evaluation helps in defining the pattern, morphology, and possible mechanism of the fractures, and consequently helps to determine the appropriate treatment strategies (Fig. 3.3). In a series of 1,199 patients evaluated by plain films and CT, 41 patients were missed by plain films and detected only by the CT; all 41 needed additional treatment.16 Computed tomography scans outperformed plain radiographs in patients with cervical trauma, with higher predictability and accuracy, and consequently CT scan is recommended as the first screening imaging for obtunded clinically unevaluable patients (high-risk patients).17–20 If high-quality CT imaging is ­available, there is no indication for extra plain radiographs. A II medical evidence study Vanguri et al21 concluded that CT is 100% sensitive in detecting bone and ligamentous injuries in blunt cervical trauma. CT alone is enough to rule out C-spine injuries without the need for additional imaging. In a retrospective study, Gargas et al22 found that MRI is not superior to multislice CT scan with sagittal and coronal reconstructions in the pediatric trauma population.



Evaluation of an Injured Cervical Spine

27

Fig. 3.1a–c  The classic three-view films: (a) odontoid, (b) lateral, and (c) anteroposterior views. Note the obscured area at the cervicothoracic junction.

a

b

c



28

Chapter 3

a

b

Fig. 3.2a,b  C1-C2 instability detected on flexion views.

Magnetic Resonance Imaging In a symptomatic patient with normal radiographs or CT scan, MRI can be used to exclude diskoligamentous injuries.23 Timing is important; it should be performed within 48 hours to detect the abnormal signals of soft tissue injuries.24 The short tau inversion recovery (STIR) sequences are suitable to evaluate the posterior ligaments and therefore confirm the type and pattern of injury. In addition, MRI has the advantages of ­assessing the spinal cord parenchyma in a ­patient with signs of traumatic myelopathy (Fig. 3.4).

In a recent study, Khanna et al24 evaluated MRI in obtunded patients (GCS < 13), without obvious neurologic deficits and normal CT scan findings. They concluded that “the addition of a cervical MRI to the evaluation protocol of obtunded or comatose patients with an otherwise normal neurologic examination and a normal cervical CT did not provide any additional useful information to change the management of these patients.” The limitations of MRI are due to the time needed to transfer the patient to the MRI suite and to obtain the evaluation, and to the dif­ ficulties involved in monitoring comatose patients who are ventilated. In addition, MRI’s



Evaluation of an Injured Cervical Spine

a

c

b

d

Fig. 3.3a–d  High-quality computed tomography (CT) scans detecting a lateral mass fracture of C3 that was missed on plain radiographs.

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Chapter 3

a

b

Fig. 3.4a,b  Magnetic resonance imaging (MRI) showing diskoligamentous injuries and cord contusion.

cost-effectiveness in these cases has not yet been proven.

■■ C-Spine Clearance

In 2001, Stiell et al25 proposed another decision-making protocol, the Canadian C-spine rule (CCR), based on a study of 8,924 awake patients admitted to trauma centers in Canada. The highly sensitive CCR utilizes three criteria (Fig. 3.5):

1. An awake, alert patient without symptoms 2. An awake and symptomatic patient 3. An obtunded clinically unevaluable patient

1. The presence of any high-risk factor that mandates radiography 2. The presence of low-risk factors that allow safe assessment of range of motion 3. The ability to actively rotate the neck 45 degrees to the left and right

In 1998, Hoffman et al10 published the decision-making rules for NEXUS (National Emergency X-Radiography Utilization Study Group) to detect the probability of a C-spine injury following trauma. According the NEXUS protocol, clearance of the C-spine can be obtained in cases with the following findings:

In 2002, a study group from the Joint Section on Disorders of the Spine and Peripheral Nerves of the American Association of Neurological Surgeons (AANS) and the Congress of Neurological Surgeons (CNS) published guidelines and recommendations for each clinical scenario following a blunt trauma26,27:

• • • • •

1. For an awake and asymptomatic patient, radiological evaluation is not recommended, and the immobilization is cleared if the patient meets the following criteria: • Alert, awake • Not intoxicated • No symptoms of neck pain or midline tenderness • No associated injuries that distract from the neck pain

On admission of a patient following a trauma, three clinical scenarios might be encountered:

No cervical pain and tenderness No neurologic deficit Normal alertness No intoxication No associated painful detracting injuries

The most important limitation of the NEXUS protocol is the reproducibility of the criteria “no intoxication” and “no painful associated injuries.”



Evaluation of an Injured Cervical Spine

The Canadian C-Spine Rule For alert (GCS=15) and stable trauma patients where cervical spine injury is a concern.

1. Any High-Risk Factor Which Mandates Radiography? Age ≥ 65 years or

Dangerous mechanism* or

Paresthesias in extremities No

Yes

2. Any Low-Risk Factor Which Allows Safe Assessment of Range of Motion? Simple rearend MVC**

No

or

Sitting position in ED

Radiography

or

Ambulatory at any time or

Delayed onset of neck pain*** or

Absence of midline c-spine tenderness

Unable

Yes

3. Able to Actively Rotate Neck? 45° left and right Able

No Radiography

* Dangerous Mechanism: -

fall from elevation ≥ 3 feet / 5 stairs axial load to head, e.g. diving MVC high speed (>100km/hr), rollover, ejection motorized recreational vehicles bicycle collision

** Simple Rearend MVC Excludes: -

pushed into oncoming traffic hit by bus / large truck rollover hit by high speed vehicle

*** Delayed: - i.e. not immediate onset of neck pain

Fig. 3.5  The Canadian C-spine rule. ED, emergency department; MVC, motor vehicle collision.

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Chapter 3 2. For awake and symptomatic patient, recommendations are to radiologically evaluate the C-spine by three-view radiographs that include anteroposterior (AP) and lateral cervical plain radiograph and an odontoid view. A CT scan is recommended if there is a suspicious image or hidden areas on the plain radiographs. In cases in which the three-view radiographs and the CT (if needed) are normal, it is recommended (level III) to perform either dynamic views or an MRI (within 48 hours). The cervical spine can be cleared if all the above exams are normal (level III). 3. In an obtunded and unevaluable patient, three-­ view radiographs, supplemented if needed by a CT scan, are systematically ordered. It is recommended (level III) that in an obtunded patient with normal radiological evaluation the C-spine is cleared only after: • Normal dynamic flexion-extension views, • Normal MRI (within 48 hours), or • At the discretion of the physician. In 2003, Stiell et al28 compared the sensitivity of the CCR versus the NEXUS and concluded with class I evidence that CCR is more sensitive than NEXUS criteria in the detection of C-spine injuries and resulted in lower rates of radiography. In 2009, the Eastern Association for Surgery of Trauma (EAST) published an updated protocol for clearing the cervical spine after blunt trauma.29 The association concluded (class I evidence) that a CT scan is the modality of choice for the primary imaging of the cervical spine trauma cases, and it is superior (in sensitivity and specificity) to the three-view plain radiographs protocol. In 2012, Rose et al30 concluded in a prospective study that even patients alert with “distracting injuries” might be cleared clinically without the need for additional imaging. Distracting injuries in the context of clearing the C-spine clinically is a myth and thus invalid. The Neck Pain Task Force graded the blunt neck injuries to determine the appropriate management31 (see text box).

Grading of Blunt Neck Injuries (According to the Neck Pain Task Force) ◆◆ Grade I: neck pain with no signs of serious pathol-

ogy and no or little interference with daily activities ◆◆ Grade II: neck pain with no signs of serious pathology, but interference with daily activities ◆◆ Grade III: neck pain with neurologic signs of nerve compression ◆◆ Grade IV: neck pain with signs of major structural pathology

The recommendations issued by the Neck Pain Task Force are illustrated in Fig. 3.6.

■■ Plain Radiographs Versus

CT Scan

The study group of the Joint Section on Disorders of the Spine and Peripheral Nerves concluded, in its 2002 recommendations,32 that the three-view cervical spine series is recommended for the evaluation of the C-spine after trauma (level I recommendation based on class I evidence). It suggests that this radiographic evaluation should be supplemented (class I evidence) by CT as necessary on suspicious or not well-visualized areas (C1-C2, C7-T1). The sensitivity of the three-view series ranged from 60 to 84%. The negative predictive value ranged from 85 to 98%, increasing to 100% when combined with dynamic views.33–36 Further studies demonstrate the superiority of CT compared with plain radiographies in detecting cervical spine injuries.37–50 In 2001, Schenarts et al39 reported a series of 1,356 patients selected prospectively according to the EAST protocol from 2,690 trauma patients and who required radiological assessment. They concluded that the CT is superior to plain films in the assessment of a traumatic cervical spine. In 2003, Griffen et al51 in a class I medical evidence study confirmed the superiority of the CT over three-view films.



Evaluation of an Injured Cervical Spine

Fig. 3.6  Recommendations for assessment and management as proposed by the Neck Pain Task Force. CT, computed tomography; ED, emergency department; ROM, range of motion.

In 2005, Holmes and Akkinepalli37 performed a meta-analysis of studies comparing CT to plain radiographies. The sensitivity of plain radiographs was 54% compared with 98% for CT. They concluded (class III evidence) that the CT is superior to plain radiographs in detecting C-spine traumatic injuries. In 2006, Daffner et al42 published a class III medical evidence (retrospective, loss of subjects) that the CT has a sensitivity of 99.2% compared with plain films’ 44.1%. In over 245 fractures, two injuries were missed by the CT but identified on the plain radiographs. Both of  these fractures were localized at C2 spinous process. The authors advocate, with no strong evidence, supplementing CT with lateral plain X-rays. They highlight the need for proper technical imaging modalities on the region of interest.

In 2007, Mathen et al41 published a class I medical evidence study concluding that the CT is superior to plain radiographs in acute injuries, and that plain films add no additional diagnostic information. Sensitivity and specificity of the CT were 100% and 99.5%, respectively, compared with 45% and 97.4% for the plain radiographs. In 2009, Bailitz et al40 published a prospective class I medical evidence study comparing cervical spine radiographs to CT. The sensitivity of the CT was 100% compared with 36% for spine radiographs. They concluded that CT is superior and should be considered as the modality of choice. In 2010, Hennessy et al,52 in a prospective study, evaluated the performance of imaging modalities in detecting C-spine injuries and

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Chapter 3 concluded that “CT of the C-spine is highly sensitive in detecting the vast majority (99.75%) of clinically significant C-spine injuries. We recommend that CT be used as the sole modality to radiographically clear the C-spine in obtunded trauma patients and do not support the use of flexion-extension radiographs as an ancillary diagnostic method.” In addition to the superiority of the CT over plain radiographs, it has been suggested that CT has the advantages also of being quicker to obtain than plain radiographs (almost half the time)43,44 and being more cost-effective45 in general because of the shorter time for evaluation and the superior sensitivity for detecting injuries with no need for additional images. These advantages overcome the higher shortterm costs of the CT. In summary, the evaluation of a symptomatic patient requires high-quality CT imaging, and there is no need for additional images such as three-view or five-view radiographs.

■■ Magnetic Resonance

Imaging

An MRI scan is superior to any other imaging modalities in detecting diskoligamentous injuries. So logically MRI might be of great help in cases of negative first-line radiological evaluation, especially if the patient could not be assessed clinically and could not undergo dynamic views. An MRI scan, including the STIR sequences, is very helpful in detecting posterior ligamentous injuries, disk herniation, spinal cord contusion, and eventually vertebral artery injuries. It is also highly sensitive in the detection of ligamentous injuries of the craniocervical junction. Many questions might be raised about the need for and value of an MRI scan in trauma patients: • Does the addition of MRI provide more information in detecting C-spine injuries?

• Does MRI impact the treatment strategy in obtunded or neurologically affected patients? In 2002, Ghanta et al53 published a retrospective study of 124 consecutive trauma patients and compared three-view plain films, CT, and MRI of the C-spine. They concluded that 22% of obtunded patients with normal plain films and CT had abnormal MRI findings (ligamentous injuries). Importantly, 6% of these injuries were unstable. In 2006, Stassen et al54 published a retrospective series of 52 patients (class III evidence). Of the 44 patients with negative CT findings, 13 had an abnormal MRI demonstrating ligamentous injuries. They concluded that CT evaluation alone is insufficient and advocate supplemental MRI. In 2008, Muchow et al55 performed a meta-­ analysis and published a class I medical evidence study that established MRI as the recommended imaging miodality to clear the C-spine despite normal plain films and CT imaging. In 2010, Menaker et al,56 in a retrospective class III study, also concluded that 8.3% of obtunded patients and 25.6% of symptomatic patients with normal CT evaluation had an ­abnormal MRI with impact on the treatment strategy. In 2010, Simon et al57 concluded in a study that the addition of MRI to CT increased the detection of C-spine injuries of trauma patients. In 2010, Schoenfeld et al58 reported a meta-­ analysis comparing CT alone to CT with MRI in detecting traumatic C-spine injuries. The series consisted of 1,550 patients with a negative CT evaluation who also had undergone MRI studies. In 12% of the cases MRI showed abnormal findings, mostly ligamentous injuries. In 6% the anomalies discovered on MRI had impact on the treatment choice. The authors concluded that MRI is useful for identifying injuries in obtunded or unevaluable patients with normal CT scan findings. In summary, in an obtunded or unevaluable patient with a normal plain radiographs and/or normal high-quality CT scan, the MRI scan seems to be the imaging modality of choice based on class II and class III medical evidence studies.



■■ Chapter Summary In assessments of C-spine clearance protocols in trauma centers in the United Kindgom59 and the United States,60 it was concluded that a significant number of centers had no clear policy, and recommended better dissemination of the guidelines and protocols through national societies. The updated level I recommendations for clearing a C-spine injuries are the following61: 1. Awake and asymptomatic patient: “The alert, asymptomatic patient without a neurologic deficit who can complete a functional range-of-motion examination and is free from other major distracting injury may safely be released from cervical spine immobilization without radiographic evaluation.” This recommendation is based on class I medical evidence supporting a level I recommendation for discontinuing cervical spine immobilization in such a situation. 2. Awake and symptomatic patient: High-quality CT scan is the modality of choice for awake and symptomatic patient. This is a level I recommendation based on class I medical evidence. If CT is not available, a three-view radiograph is recommended (level I). If CT is normal in a symptomatic patient, class II and class III medical evidence studies recommend three different strategies: • Maintain cervical immobilization until patient is asymptomatic. • Perform dynamic radiographs and/or MRI within 48 hours. • Clear the C-spine at the discretion of the attending physician.

Evaluation of an Injured Cervical Spine 3. Obtunded, unevaluable patient: The level I recommendation in a patient that is not clinically examinable is to obtain a high-quality CT scan. If the CT is not available, a three-view plain radiograph is recommended. In an obtunded patient who had normal CT or normal radiographs, MRI seems to be appropriate evaluation based on class II and class III medical evidence studies. In such a scenario, cervical immobilization can be discontinued if MRI within 48 hours is normal. Pearls ◆◆ Rapid discontinuation, within 72 hours, of cervi-

cal immobilization is recommended.

◆◆ The alert, asymptomatic patient without a neuro-

logic deficit who can complete a functional range-­ of-motion examination and is free from other major distracting injury may safely be released from cervical spine immobilization without a radiological evaluation. ◆◆ In an awake and symptomatic patient, a high-­ quality CT scan may rule out traumatic and unstable C-spine injuries. ◆◆ In an obtunded and unevaluable patient, high-­ quality CT scan is first recommended in addition to MRI if the CT is normal. Pitfalls ◆◆ Missed C-spine injuries might have catastrophic

consequences.

◆◆ Avoid prophylactically extended C-spine immobi-

lization (especially in comatose patients).

◆◆ Avoid excessive and unnecessary imaging studies

for fear of hidden injuries.

References

Five Must-Read References 1. Grossman MD, Reilly PM, Gillett T, Gillett D. National survey of the incidence of cervical spine ­injury and approach to cervical spine clearance in U.S. trauma centers. J Trauma 1999;47:684–690 PubMed

2. Davis JW, Phreaner DL, Hoyt DB, Mackersie RC. The etiology of missed cervical spine injuries. J Trauma 1993;34:342–346 PubMed 3. Goldberg W, Mueller C, Panacek E, Tigges S, Hoffman JR, Mower WR; NEXUS Group. Distribution and pat-

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Chapter 3 terns of blunt traumatic cervical spine injury. Ann Emerg Med 2001;38:17–21 PubMed 4. Harris TJ, Blackmore CC, Mirza SK, Jurkovich GJ. Clearing the cervical spine in obtunded patients. Spine 2008;33:1547–1553 PubMed 5. Richards PJ. Cervical spine clearance: a review. Injury 2005;36:248–269, discussion 270 PubMed 6. Lekovic GP, Harrington TR. Litigation of missed cervical spine injuries in patients presenting with blunt traumatic injury. Neurosurgery 2007;60:516–522, discussion 522–523 PubMed 7. Widder S, Doig C, Burrowes P, Larsen G, Hurlbert RJ, Kortbeek JB. Prospective evaluation of computed tomographic scanning for the spinal clearance of obtunded trauma patients: preliminary results. J Trauma 2004;56:1179–1184 PubMed 8. Ajani AE, Cooper DJ, Scheinkestel CD, Laidlaw J, Tuxen DV. Optimal assessment of cervical spine trauma in critically ill patients: a prospective evaluation. Anaesth Intensive Care 1998;26:487–491 PubMed 9. Ackland HM, Cooper DJ, Malham GM, Kossmann T. Factors predicting cervical collar-related decubitus ulceration in major trauma patients. Spine 2007; 32:423–428 PubMed 10. Hoffman JR, Wolfson AB, Todd K, Mower WR. Selective cervical spine radiography in blunt trauma: methodology of the National Emergency X-Radiography Utilization Study (NEXUS). Ann Emerg Med 1998; 32:461–469 PubMed 11. Committee on the Biological Effects of Ionizing Radiations, Board on Radiation Effects Research, Commission on Life Sciences (BEIR V). Health Effects of Exposure to Low Levels of Ionizing Radiation. Washington, DC: National Academy Press; 1990:281 12. Hoffman JR, Schriger DL, Mower W, Luo JS, Zucker M. Low-risk criteria for cervical-spine radiography in blunt trauma: a prospective study. Ann Emerg Med 1992;21:1454–1460 PubMed 13. Mower WR, Hoffman JR, Schriger DL. The feasibility of selective radiography in patients with trauma-­ induced neck pain. Ann Emerg Med 1990;19(Suppl): 1220–1221 Abstract 14. Streitwieser DR, Knopp R, Wales LR, Williams JL, Tonnemacher K. Accuracy of standard radiographic views in detecting cervical spine fractures. Ann Emerg Med 1983;12:538–542 PubMed 15. Chiu WC, Haan JM, Cushing BM, Kramer ME, Scalea TM. Ligamentous injuries of the cervical spine in unreliable blunt trauma patients: incidence, evaluation, and outcome. J Trauma 2001;50:457–463, discussion 464 PubMed 16. Griffen MM, Frykberg ER, Kerwin AJ, et al. Radiographic clearance of blunt cervical spine injury: plain radiograph or computed tomography scan? J Trauma 2003;55:222–226, discussion 226–227 PubMed 17. Holmes JF, Akkinepalli R. Computed tomography versus plain radiography to screen for cervical spine

injury: a meta-analysis. J Trauma 2005;58:902–905 PubMed 18. Diaz JJ Jr, Gillman C, Morris JA Jr, May AK, Carrillo YM, Guy J. Are five-view plain films of the cervical spine unreliable? A prospective evaluation in blunt trauma patients with altered mental status. J Trauma 2003; 55:658–663, discussion 663–664 PubMed 19. Griffen MM, Frykberg ER, Kerwin AJ, et al. Radiographic clearance of blunt cervical spine injury: plain radiograph or computed tomography scan? J Trauma 2003;55:222–226, discussion 226–227 PubMed 20. Suzuki T, Morimura N, Sugiyama M, Kitahara T, Soma K. How often should computed tomographic scans following cross-table lateral cervical films be performed? J Orthop Surg (Hong Kong) 2004;12: 40–44 PubMed 21. Vanguri P, Young AJ, Weber WF, et al. Computed tomographic scan: it’s not just about the fracture. J Trauma Acute Care Surg 2014;77:604–607 22. Gargas J, Yaszay B, Kruk P, Bastrom T, Shellington D, Khanna S. An analysis of cervical spine magnetic resonance imaging findings after normal computed tomographic imaging findings in pediatric trauma patients: ten-year experience of a level I pediatric trauma center. J Trauma Acute Care Surg 2013;74: 1102–1107 23. Richards PJ. Cervical spine clearance: a review. Injury 2005;36:248–269, discussion 270 PubMed 24. Khanna P, Chau C, Dublin A, Kim K, Wisner D. The value of cervical magnetic resonance imaging in the evaluation of the obtunded or comatose patient with cervical trauma, no other abnormal neurological findings, and a normal cervical computed tomography. J Trauma Acute Care Surg 2012;72:699–702 25. Stiell IG, Wells GA, Vandemheen KL, et al. The Canadian C-spine rule for radiography in alert and stable trauma patients. JAMA 2001;286:1841–1848 PubMed 26. Radiographic assessment of the cervical spine in asymptomatic trauma patients. Neurosurgery 2002; 50(3 suppl):S30–S35 27. Radiographic assessment of the cervical spine in symptomatic trauma patients. Neurosurgery 2002; 50(3 suppl):S36–S43 28. Stiell IG, Clement CM, McKnight RD, et al. The Canadian C-spine rule versus the NEXUS low-risk criteria in patients with trauma. N Engl J Med 2003;349: 2510–2518 PubMed 29. Como JJ, Diaz JJ, Dunham CM, et al. Practice management guidelines for identification of cervical spine injuries following trauma: update from the eastern association for the surgery of trauma practice management guidelines committee. J Trauma 2009;67: 651–659 PubMed 30. Rose MK, Rosal LM, Gonzalez RP, et al. Clinical clearance of the cervical spine in patients with distracting injuries: it is time to dispel the myth. J Trauma Acute Care Surg 2012;73:498–502

31. Guzman J, Haldeman S, Carroll LJ, et al; Bone and Joint Decade 2000–2010 Task Force on Neck Pain and Its Associated Disorders. Clinical practice implications of the Bone and Joint Decade 2000–2010 Task Force on Neck Pain and Its Associated Disorders: from concepts and findings to recommendations. Spine 2008;33(4, Suppl):S199–S213 PubMed 32. Radiographic assessment of the cervical spine in symptomatic trauma patients. Neurosurgery 2002; 50(3, Suppl):S36–S43 PubMed 33. Berne JD, Velmahos GC, El-Tawil Q, et al. Value of complete cervical helical computed tomographic scanning in identifying cervical spine injury in the unevaluable blunt trauma patient with multiple injuries: a prospective study. J Trauma 1999;47:896– 902, discussion 902–903 PubMed 34. Ajani AE, Cooper DJ, Scheinkestel CD, Laidlaw J, Tuxen DV. Optimal assessment of cervical spine trauma in critically ill patients: a prospective evaluation. Anaesth Intensive Care 1998;26:487–491 PubMed 35. Davis JW, Parks SN, Detlefs CL, Williams GG, Williams JL, Smith RW. Clearing the cervical spine in obtunded patients: the use of dynamic fluoroscopy. J Trauma 1995;39:435–438 PubMed 36. MacDonald RL, Schwartz ML, Mirich D, Sharkey PW, Nelson WR. Diagnosis of cervical spine injury in motor vehicle crash victims: how many X-rays are enough? J Trauma 1990;30:392–397 PubMed 37. Holmes JF, Akkinepalli R. Computed tomography versus plain radiography to screen for cervical spine injury: a meta-analysis. J Trauma 2005;58:902–905 PubMed 38. Diaz JJ Jr, Gillman C, Morris JA Jr, May AK, Carrillo YM, Guy J. Are five-view plain films of the cervical spine unreliable? A prospective evaluation in blunt trauma patients with altered mental status. J Trauma 2003; 55:658–663, discussion 663–664 PubMed 39. Schenarts PJ, Diaz J, Kaiser C, Carrillo Y, Eddy V, Morris JA Jr. Prospective comparison of admission computed tomographic scan and plain films of the upper cervical spine in trauma patients with altered mental status. J Trauma 2001;51:663–668, discussion 668–669 PubMed 40. Bailitz J, Starr F, Beecroft M, et al. CT should replace three-view radiographs as the initial screening test in patients at high, moderate, and low risk for blunt cervical spine injury: a prospective comparison. J Trauma 2009;66:1605–1609 PubMed 41. Mathen R, Inaba K, Munera F, et al. Prospective evaluation of multislice computed tomography versus plain radiographic cervical spine clearance in trauma patients. J Trauma 2007;62:1427–1431 PubMed 42. Daffner RH, Sciulli RL, Rodriguez A, Protetch J. Imaging for evaluation of suspected cervical spine trauma: a 2-year analysis. Injury 2006;37:652–658 PubMed 43. Daffner RH. Cervical radiography for trauma patients: a time-effective technique? AJR Am J Roentgenol 2000;175:1309–1311 PubMed

Evaluation of an Injured Cervical Spine 44. Daffner RH. Helical CT of the cervical spine for trauma patients: a time study. AJR Am J Roentgenol 2001; 177:677–679 PubMed 45. Blackmore CC. Evidence-based imaging evaluation of the cervical spine in trauma. Neuroimaging Clin N Am 2003;13:283–291 PubMed 46. Padayachee L, Cooper DJ, Irons S, et al. Cervical spine clearance in unconscious traumatic brain injury patients: dynamic flexion-extension fluoroscopy versus computed tomography with three-dimensional reconstruction. J Trauma 2006;60:341–345 PubMed 47. Spiteri V, Kotnis R, Singh P, et al. Cervical dynamic screening in spinal clearance: now redundant. J Trauma 2006;61:1171–1177, discussion 1177 PubMed 48. Griffiths HJ, Wagner J, Anglen J, Bunn P, Metzler M. The use of forced flexion/extension views in the obtunded trauma patient. Skeletal Radiol 2002;31:587– 591 PubMed 49. Bolinger B, Shartz M, Marion D. Bedside fluoroscopic flexion and extension cervical spine radiographs for clearance of the cervical spine in comatose trauma patients. J Trauma 2004;56:132–136 PubMed 50. Davis JW, Kaups KL, Cunningham MA, et al. Routine evaluation of the cervical spine in head-injured patients with dynamic fluoroscopy: a reappraisal. J Trauma 2001;50:1044–1047 PubMed 51. Griffen MM, Frykberg ER, Kerwin AJ, et al. Radiographic clearance of blunt cervical spine injury: plain radiograph or computed tomography scan? J Trauma 2003;55:222–226, discussion 226–227 PubMed 52. Hennessy D, Widder S, Zygun D, Hurlbert RJ, Burrowes P, Kortbeek JB. Cervical spine clearance in obtunded blunt trauma patients: a prospective study. J Trauma 2010;68:576–582 PubMed 53. Ghanta MK, Smith LM, Polin RS, Marr AB, Spires WV. An analysis of Eastern Association for the Surgery of Trauma practice guidelines for cervical spine evaluation in a series of patients with multiple imaging techniques. Am Surg 2002;68:563–567, discussion 567–568 PubMed 54. Stassen NA, Williams VA, Gestring ML, Cheng JD, Bankey PE. Magnetic resonance imaging in combination with helical computed tomography provides a safe and efficient method of cervical spine clearance in the obtunded trauma patient. J Trauma 2006;60: 171–177 PubMed 55. Muchow RD, Resnick DK, Abdel MP, Munoz A, Anderson PA. Magnetic resonance imaging (MRI) in the clearance of the cervical spine in blunt trauma: a meta-analysis. J Trauma 2008;64:179–189 PubMed 56. Menaker J, Stein DM, Philp AS, Scalea TM. 40-slice multidetector CT: is MRI still necessary for cervical spine clearance after blunt trauma? Am Surg 2010; 76:157–163 PubMed 57. Simon JB, Schoenfeld AJ, Katz JN, et al. Are “normal” multidetector computed tomographic scans sufficient

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Chapter 3 to allow collar removal in the trauma patient? J Trauma 2010;68:103–108 PubMed 58. Schoenfeld AJ, Bono CM, McGuire KJ, Warholic N, Harris MB. Computed tomography alone versus computed tomography and magnetic resonance imaging in the identification of occult injuries to the cervical spine: a meta-analysis. J Trauma 2010;68:109–113, discussion 113–114 PubMed 59. Mercer SJ, Guha A. Assessing the implementation of guidelines for the management of the potentially injured cervical spine in unconscious trauma patients in England. J Trauma 2010;68:1445–1450 PubMed

60. Theologis AA, Dionisio R, Mackersie R, McClellan RT, Pekmezci M. Cervical spine clearance protocols in level 1 trauma centers in the United States. Spine 2014;39:356–361 PubMed 61. Timothy C. Guidelines for the management of acute cervical spine and spinal cord injuries: 2013 update. Radiographic Assessment; American Association of Neurological Surgeons; Congress of Neurological Surgeons. Neurosurgery 2013;72:54–72

4 Nonoperative Management of Cervical Spine Trauma Peter Formby and Melvin D. Helgeson

■■ Introduction Cervical fractures are common injuries encountered in a trauma setting, and fractures to this area can have damaging consequences, including traumatic spinal cord injuries. It is estimated that 150,000 cervical spine injuries occur annually in North America. The subaxial spine accounts for the majority of cervical injuries, making up 65% of fractures and more than 75% of all dislocations.1 Isolated fractures of C1 and C2 account for 5% and 20% of cervical fractures, respectively, whereas fractures of the occipital condyles are estimated to occur in 1% of craniocervical traumas.2,3 A significant number of these injuries can be treated nonoperatively with immobilization.

■■ Initial Assessment Upon the patient’s arrival at the treating facility, a history is taken to determine comorbidities and the mechanism of injury. If possible, a complete radiographic evaluation of the patient should be performed, which should include a cross-table lateral view of the cervical spine with visualization of the occiput-T1 levels. A swimmer’s view may be necessary if the lower cervical spine is not completely visualized. A lateral view of the entire spine should also be obtained, as noncontiguous spinal injuries are

very common. Based on these initial images or on clinical suspicion, the patient may be scheduled for a computed tomography (CT) scan, which has demonstrated a greater sensitivity (100%) than that of lateral radiographs (63%) in detecting fractures of the cervical spine.4 In the patient with no neurologic deficits or radicular pain, magnetic resonance imaging (MRI) may not provide any additional information required for patient management. Although this is a controversial issue, Tomycz and colleagues5 found that MRI was not useful in uncovering unstable cervical spine injuries even in comatose and obtunded patients. However, MRI is routinely obtained in patients with traumatic cervical spine injuries.

■■ Skeletal Traction Closed reduction of the cervical spine has been performed in modern practice since 1929, when Taylor6 first used a halter to reduce a cervical dislocation. Gardner-Wells tongs were first described in 1973, and are the most frequently used device in the modern era for initial closed cervical skeletal traction. Reduction can restore osseous alignment, decompress the spinal cord and nerve roots, and maintain stability. Surgery can occasionally, but rarely, be avoided following successful closed reduction. Following a traumatic cervical spine fracture with spinal



40

Chapter 4 cord or nerve impingement, decompression should be performed as soon a possible to prevent further damage and to enable the maximum possible recovery. The typical method of reduction involves the application of Gardner-­ Wells tongs to the skull. The position of the pins is typically 1 cm above each pinna, below the equator of the skull. A more anterior pin placement results in cervical extension, and a posterior placement results in cervical flexion, which may be necessary depending on the fracture pattern and displacement. Pins should be placed perpendicular to the skull to achieve maximal mechanical advantage and avoid pullout and toggling. Ideally, attempts at closed reduction should be performed in an awake and oriented patient who can participate in a neurologic exam. Before application of weights, a cross-table lateral cervical spine film should be taken and a baseline neurologic exam should be performed. Under expert guidance, increments of 10 lb of distraction force are applied. Consideration should be given to potential nasotracheal intubation if reducing a posterior type II dens fracture, as there is a reported 40% incidence of respiratory deterioration from airway obstruction if the cervical spine is flexed during reduction.7 After each distraction event, a repeat lateral view of the cervical spine is taken and a repeat neurologic evaluation is performed. If there are indications that the disk spaces are distracting, weighted distraction should be decreased as overdistraction may occur, which risks further neurologic injury. Once reduction is achieved, the lowest amount of weight is used to maintain reduction. The safe application of weights up to 140 lb has been documented to achieve reduction in the lower cervical spine.8 Next, the patient should receive an MRI to further evaluate the diskoligamentous integrity of the cervical spine. In the unconscious or obtunded patient, it is generally agreed that an MRI should be obtained on an urgent basis to search for neurologic compression, and no attempt at closed reduction should be performed given the risk of further injury. But there is significant controversy regarding obtaining an MRI prior to reduction of the cervical spine in the alert, awake,

and oriented patient. In one report, an alert 54-year-old man suffered acute quadriplegia following closed traction of a bilateral cervical facet dislocation. There was no pre-reduction MRI, and he had known ossification of the posterior longitudinal ligament. He had full neurologic recovery, however, after open decompression and stabilization.9 Vaccaro and associates10 obtained pre-reduction MRIs on 11 patients prior to awake closed traction reduction and found that two of the 11 had disk herniations prior to reduction and five had disk herniations following closed reduction, though none had neurologic deterioration following the procedure. Grant et al11 reviewed 82 patients with cervical spine fracture-dislocations and found that pre-reduction MRI showing disk herniation or disruption conferred no worse a neurologic outcome following closed reduction on alert patients, and therefore they did not recommend pre-reduction MRI.

■■ Cervical Orthoses Cervical orthoses are a group of externally applied devices that function by restricting ­ motion indirectly and act to stabilize and support the spine. They are used for early motion restriction after acute trauma, in the postoperative period for additional stability/comfort, and as definitive treatment in generally stable patients without neurologic deficits. Orthoses provide the paraspinal muscles with proprioceptive feedback to limit motion and maintain proper anatomic positioning. Most cervical orthoses exert flexion/extension control to varying degrees, but are more limited in their rotatory and coronal lateral bending control. There is an inverse relationship between the amount of discomfort/rigidity of an orthosis and tolerance by a patient, so it important to match the orthosis to the proper injury and patient. In the cervical spine, devices are commonly referred to as either cervical orthoses (COs) or cervical thoracic orthoses (CTOs) depending on the levels to which the device extends. In general, studies regarding the stability afforded



Nonoperative Management of Cervical Spine Trauma

by various orthoses are difficult to interpret as a whole, given the varying means used to measure angular and translational motions, outdated or discontinued orthoses, as well as the measured specimens themselves (i.e., healthy volunteers vs cadavers). Cervical orthoses are the most comfortable orthoses when composed of soft material such as foam, but they provide limited stability to the cervical spine (Fig. 4.1). They mainly function by providing tactile feedback to the patient, limiting drastic and extreme voluntary cervical motion. They are often used in cases of cervical muscle strain or soft tissue sprain, or in the postoperative period for comfort. In a recent study comparing soft and rigid collars in 15 activities of daily living (ADL), soft collars were found to limit mean flexion/extension by 27.1%, lateral bending by 26.1%, and rotation by 29.3%.12 The corresponding reductions in motion with a rigid collar were greater at 53.7%, 34.9%, and 59.2%, though no significant difference in motion between these two devices was noted in 13 of 15 ADLs. These findings indicate that patients likely self-regulate their neck movements based on comfort, and that rigid collars are not always necessary, particularly postoperatively if the construct is stable. Rigid collars are one of the mainstays of early cervical trauma immobilization and often pro-

Fig. 4.1  An example of a soft cervical collar.

vide the means for definitive treatment. Some examples of rigid COs include the Philadelphia collar, the Miami-J, the Aspen cervical orthosis, the PMT® CervMax™ Cervical Orthosis Collar (PMT Corporation, Chanhassen, MN), and the Vista collar (Figs. 4.2 and 4.3). In contrast, CTOs extend down the thorax to varying degrees and generally confer a greater amount of stability to the cervical spine. Some common examples of CTOs include the Lerman Minerva cervical orthosis, the sterno-occipito-mandibular immobilizer (SOMI), the Aspen 2- and 4-post, and the Vista TS and TS4 CTOs. A three-dimensional (3D) motion analysis of five COs (Aspen, Aspen Vista, Philadelphia, Miami-J, and Miami-J Advanced) found that the Aspen best restricted sagittal, axial, and coronal motion.13 The Vista collar was found to be the least restrictive in all motions. Other studies have found the Philadelphia and Miami-J collars to be more restrictive than the Aspen collar.14 In a study comparing the Miami-J and Aspen COs to the Aspen 4-post and Aspen 2-post CTOs, the authors found no significant difference in angular C0-C7 motion between the two COs, though the Miami-J allowed more motion at C5–6.15 The two CTOs limited flexion to a similar degree, but the Aspen 4-post limited angular and translational motion in extension to a greater degree (38% vs 22% and 50% vs 24%, respectively). In a similar study using cadavers with flexion-compression fractures at the lower cervical spine level and extension-­ compression at the upper cervical spine level, Ivancic16 evaluated two COs (Vista collar and Vista multipost collar) and 2 CTOs (Vista TS and Vista TS4). Predictably, successively greater restriction in extension and flexion in the upper and lower cervical spines, respectively, was obtained using the CTOs. The Vista collar and Vista TS4 collar showed the least and greatest restriction, respectively. Schneider et al17 evaluated four COs and three CTOs on healthy adult volunteers in the supine and standing positions. The subjects found the Miami-J and Aspen collars to be the most comfortable, and, in general, all COs were rated more comfortable than CTOs. As expected, the CTOs limited motion at all levels to a greater degree than COs. The Minerva was the most effective at limiting

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Chapter 4

Fig. 4.2  An Aspen rigid cervical orthosis.

Fig. 4.3  A Miami-J rigid cervical orthosis.

intervertebral motion at all levels. Of the cervical orthoses, the Philadelphia was the most effective cervical orthosis at all levels except C6-C7, where the PMT performed better. The Lerman halo was the most effective at limiting overall axial rotation and coronal bending, whereas the Philadelphia was the best CO in these same planes. Indeed, almost all studies indicate that stability increases as the level of orthosis restriction increases.18 When prescribing a cervical orthosis, the benefits of its motion restriction must be weighed against the complications. One major complication is cervical collar–related decubitus ulceration, which has been found to increase 66% for every 1-day increase in collar use.19 In one study comparing craniofacial tissue pressures between four COs, Miami-J collars conferred less occipital and mandibular pressures compared with Philadelphia and Aspen collars.14 Other complications include dysphagia, increased intracranial pressure, and decreased mouth opening with semirigid orthoses, which could potentially limit definitive airway placement in an unstable patient. A drawback of

many cervical braces such as the Minerva brace is the motion seen in the upper cervical spine occiput–C4 level with mastication. To limit this phenomenon, it is recommended to patients that they temporarily remove the mandibular component while chewing.

■■ Halo Immobilization The halo fixator is a versatile instrument for managing cervical spine fractures. This device can be used for temporary closed reduction and stability prior to surgery, as the definitive treatment for many cervical spine fractures, and as a supplement for additional stability after cervical fusions. The halo fixation vest is generally espoused as one of the most rigid external stabilizing devices of the cervical spine, limiting cervical spine motion to between 30% and 90%. One of the reported weaknesses of the halo fixation vest is its inability to adequately immobilize the occiput–C1 interface, with one report showing 8 degrees of angula-



Nonoperative Management of Cervical Spine Trauma

tion at this level.20 Another in-vivo study found halo fixation limited maximum motion to 70% of normal motion, though the least restraint was above the C2 level.21 However, it has been shown to be safe and effective in treating fractures and dislocations in the upper cervical spine C1-C2. The conventional halo vest itself consists of a complete or U-shaped metal ring, four pins, a vest with anterior and posterior components, four upright struts, and four fixation rods. To apply the device, the patient is placed in the supine position with stacked towels placed behind the torso, neck, and head. The head and neck are manually stabilized in neutral position by at least one assistant. The appropriately sized ring should ideally allow < 1 cm of clearance from all aspects of the head, just below the equator of the skull, and no portion of the ring should contact the patient’s skin. The anterior pins should be placed in the safe zone, ~ 0.5 to 1 cm above the lateral one third of the eyebrows. A more medial placement can injure the adjacent supraorbital and supratrochlear nerves, and more lateral placement can pierce the masseter muscle and potentially penetrate the thin temporalis fossa. Pins should be placed perpendicular to the skull to maximize the pin–bone interface, and patients should be instructed to close their eyes to avoid tenting the orbicularis oculi muscles. The posterior pins should be placed ~ 180 degrees from their corresponding anterior pins. There are no major concerns when placing the posterior pins due to the thickness of the posterolateral skull in this region (9.47 ± 1.12 mm). A cadaveric study found that the maximum safe torque anterolaterally and posterolaterally was 8 inch-lb and 18 inch-lb, respectively.22 A separate study showed a decreased complication trend with no increased pin loosening or infection when 6-inch-lb torque was used instead of 8-inch-lb.23 No skin incision is necessary and the pins are alternately tightened until 8 inch-lb of torque are obtained. The posterior aspect of the vest in then placed by logrolling the patient while the head is manually held in neutral position. The patient is again placed supine and the anterior aspect of the vest is clamped in place and

the upright struts are connected to the vest and ring. A hand should be able to fit snugly between the vest and chest to demonstrate safe excursion for breathing and to prevent skin necrosis. A supine and upright lateral of the cervical spine is then obtained to ensure adequate stabilization without fracture displacement. The pins are retightened at 24 to 48 hours and again at 1 week to prevent loosening. In a review of halo vest immobilization, Vieweg and Schultheiss24 recommended the utility of halo vest immobilization for the treatment of patients with isolated Jefferson fractures, hangman’s fractures, and odontoid type II and type III fractures, with a low dislocation rate. However, there was an unsatisfactory healing rate when it was used to treat combined injuries with an odontoid type II fracture. Tashjian et al25 found that there was a significantly higher morbidity and mortality rate (42% vs 20% mortality rate) when treating type II and III dens fractures in elderly patients (> 65 years of age) with halo fixation compared with rigid cervical orthoses or operative fixation. In an in-vivo study comparing flexion and extension radiographs in 20 patients immobilized with either a modified 12-pin halo vest fixation or a Philadelphia collar, there was a significant advantage of the halo vest in limiting subaxial sagittal plane motion, though there was no difference found between flexion/extension at the C1-C2 levels. Normal atlantoaxial motion was restricted by 88.5% with the Philadelphia collar compared with 70.8% with the halo vest fixation.26 An in-vitro study of intact and simulated type II dens fractures found that halo vest immobilization was superior to soft collar, Miami-J collar, and Minerva brace in all planes of motion at the C1–C3 levels.27 In a review of patients with type II and type III dens fractures treated with either a halo vest or rigid cervical collar, Polin et al28 found excellent healing in type III fractures regardless of immobilization means and no significant difference in osseous union despite collar patients being older (68 vs 44 years) in type II fractures. A radiographic study of 10 patients with various cervical spine fractures initially treated in a halo fixation vest for 6 to 8 weeks and then transitioned to a

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Chapter 4 Minerva brace found a mean vertebral motion average from the occiput to C7 was lower in the Minerva than in the halo (2.3 vs 3.7 degrees) and that eight of 10 patients preferred the Minerva brace. Additionally the “snaking” phenomenon, in which there are paradoxical alternate rotations throughout the cervical spine, was seen in both orthoses, but to a larger degree in the halo device.29

Complications Numerous complications have been associated with halo vest fixation, including fracture nonunion, pin loosening, superficial infection, pressure sores, nerve injury, dysphagia, pin discomfort, scar, intracranial penetration, epidural abscess, and allergic reactions to the pins. One of the most widely reported problems with halo vest fixation is the unacceptable complications associated with its use in elderly patients. Majercik et al30 reported a 40% mortality rate in 109 patients > 65 years of age compared with 2% in 289 younger patients despite a higher injury severity score in the younger cohort. The most common complication is pin loosening (36–60%). In a biomechanical and in-vivo study, the compressive force of the pins was found to decrease by 83% in cadavers and 88% in vivo over a 3-month wear period.31,32 Loose pins should be retightened to 8 inch-lb if possible; otherwise, replacement to an adjacent site is indicated. Studies have also reported that the snaking phenomenon can potentially lead to delayed union or nonunion. Biomechanical studies have shown that physiological motion is largely maintained with a properly fitting vest, however. Superficial infections at pin sites are managed with local pin care and oral antibiotics. More severe infections require pin removal, repositioning, incision and drainage, and possible parenteral antibiotics. Kim et al33 recommended obtaining supine and upright lateral films while the patient is in the halo vest after placement and then at 2 weeks, 6 weeks, and 3 months to aid in identifying a change in fracture displacement ≥ 5 mm to identify patients at risk for treatment failure. Dysphagia is typically in-

duced by cervical extension, and may necessitate adjustments to the upright struts.

■■ General Treatment

Principles

Cervical Sprains Cervical sprains are frequently due to hyper­ extension whiplash-type injuries sustained in motor vehicle collisions. Often the soft tissue support structure of the cervical spine, including the muscular, ligamentous, and capsular structures, is stretched or partially torn in the traumatic event. When the head is turned to the right or left, the contralateral sternocleidomastoid has been shown to have the greatest contraction, which potentially exposes this muscle to damage.34 The treatment for whiplash-­ type injuries is generally a soft cervical collar for proprioceptive limitation of extreme neck movement during the healing process. One study found no difference, however, in clinical recovery when comparing 3 weeks of soft collar immobilization to early mobilization following soft tissue neck injuries. In fact, the immobilized group had a statistically longer return to work after injury (34 days vs 17 days).35

Upper Cervical Spine Nonoperative management of the upper cervical spine (occiput–C2 levels) is commonplace. Following closed reduction, many fractures at these levels can be managed by rigid immobilization unless grossly unstable or with an associated neurologic injury requiring decompression. The classification and surgical indications for each fracture pattern are discussed in subsequent chapters. The majority of occipital condyle fractures can be treated nonoperatively with rigid or semirigid immobilization unless there are concomitant fractures or gross ligamentous instability. Maddox et al36 retrospectively reviewed the nonoperative management of Anderson and Montesano types I to III and found no associa-



Nonoperative Management of Cervical Spine Trauma

tion between neck disability index scores and fracture type, displacement of fracture, sex, bilaterality, or presence of head injury. Similarly, most fractures of the atlas (7% of all cervical spine fractures) can be treated with rigid collar or halo immobilization based largely on whether or not the transverse ligament in intact. There is significant controversy regarding the method of immobilization, though either method has documented success. The dens fracture is the most common fracture of the axis, occurring in a bimodal distribution in the young and elderly populations via high- and low-impact trauma, respectively. Anderson and D’Alonzo type I to III fractures have all been managed nonoperatively in either rigid cervical orthoses or halo vest immobilization depending on the associated injuries, transverse ligament integrity, the Hadley type IIA classification, and the direction and degree of displacement (> 6 mm) of the dens. It is generally agreed that in the elderly population, halo immobilization is associated with increased morbidity and mortality, though there have been good outcomes with halo immobilization in patients over 65 years of age.37 The literature offers conflicting findings regarding the increased mortality rates in elderly patients with nonoperative management compared with operative stabilization. In a recent study by Molinari et al,38 elderly patients with ≥ 50% displacement of the dens were treated with posterior fusion and those with < 50% displacement were treated with rigid cervical collars. The authors found a higher fusion rate in operative patients, but lower neck disability scores, less pain, fewer complications, and a lower mortality rate (12% vs 20%) in the nonoperative group. Hangman’s fractures are also commonly treated nonoperatively. In a retrospective review of 27 type II and four type IIA hangman’s fractures, Vaccaro et al39 found that nonoperative treatment with halo immobilization led to union in 21 of the type II and all of the type IIA fractures, though patients with initial angulation ≥ 12 mm required reapplication of traction before union. Li et al40 found that nonoperative management was acceptable for most fracture

patterns, though fixation should be considered for severely displaced Levine-Edwards type IIa and III fractures.

Subaxial Spine Trauma Like the upper cervical spine, nonoperative treatment of the subaxial (C3-C7) spine is commonplace unless there is gross instability or neurologic injury requiring decompression. Facet fractures are one example of a fracture for which the treating physician may consider surgical intervention, as patients treated nonoperatively seem to experience greater pain and disability than those managed operatively. Unilateral facet fractures make up 6 to 10% of all cervical spine fractures, with one report indicating that the C7 facet is the most commonly injured level (68%). Halliday et al41 suggested that there may be utility in obtaining an MRI to evaluate the facet region, the interspinous ligament, the anterior longitudinal ligament, and the posterior longitudinal ligament. Injury to three of these four ligament complexes conferred a higher risk for instability and the potential need for surgery. A separate study indicated that fracture instability and possible nonoperative failure may be determined if the facet fracture involves > 40% of the absolute height of the intact lateral mass or an absolute height > 1 cm.42

Gunshot Wounds Gunshot-related fractures of the cervical spine are uncommonly encountered and are often treated nonoperatively, as these are usually stable injuries. These injuries can be complicated by emergent bleeding and airway obstruction that may preclude typical spine immobilization. In a review of 10 patients with atlantoaxial gunshot wounds, all but two injuries involved the vertebral artery. Only one patient required operative fusion of the spine, one received halo immobilization, one required fragment removal, and one required embolization following a fistula.43 All ultimately had a mechanically stable spine. In a separate review of 81 patients with gunshot wounds to the head

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Chapter 4 or neck, 19 patients were identified as having cervical spine fractures.44 Of the alert and awake patients, only three were identified as having a cervical spine fracture, and none of these were unstable. The authors’ conclusions were that spinal precautions should not interfere with lifesaving procedures, particularly in the alert and oriented patient.

creasing patient discomfort and complications as stability increases. Pearls ◆◆ The majority of cervical spine injuries occur in the

subaxial cervical spine.

◆◆ Rigid immobilization is required after injury to

ensure that no additional damage occurs.

◆◆ The majority of cervical spine injuries are man-

■■ Chapter Summary Cervical spine fractures are common injuries seen in the trauma setting, and proper recognition and treatment of injuries to this region are integral to prevent further damage. Immobilization followed by radiographic and often CT/ MRI scans are the mainstay of initial treatment. Cervical traction with either Gardner-Wells tongs or a halo device are modalities used to reduce fracture dislocations and to relieve cord compression. The majority of cervical spine trauma is managed nonoperatively with cervical immobilization. The rigidity and vertebral levels spanned by the orthosis is largely up to the treating physician, who must consider in-

aged nonoperatively.

◆◆ There remains significant controversy regarding

performing an MRI prior to reduction of the cervical spine in the alert, awake, and oriented patient. ◆◆ Closed reduction should be performed under expert guidance in an awake and oriented patient who can participate in a neurologic exam. ◆◆ In general, stability increases as the level of cervical orthosis restriction increases. Pitfalls ◆◆ Ensure proper plain X-ray imaging prior to any

closed reduction attempt.

◆◆ Decubitus ulceration is a major but preventable

complication of cervical immobilization.

◆◆ Use caution when considering application of halo

vest immobilization for elderly patients.

References

Five Must-Read References 1. Vaccaro AR, Hulbert RJ, Patel AA, et al; Spine Trauma Study Group. The subaxial cervical spine injury classification system: a novel approach to recognize the importance of morphology, neurology, and integrity of the disco-ligamentous complex. Spine 2007;32: 2365–2374 PubMed 2. Noble ER, Smoker WR. The forgotten condyle: the appearance, morphology, and classification of occipital condyle fractures. AJNR Am J Neuroradiol 1996; 17:507–513 PubMed 3. Sayadipour A, Anderson D, Mlyavykh S, Perlmutter O, Vaccaro A. Subaxial cervical spine injuries. In: Benzel EC (ed). Spine Surgery: Techniques, Complication Avoidance and Management, vol 3. Philadelphia: Elsevier; 2012:611–624.  4. Platzer P, Jaindl M, Thalhammer G, et al. Clearing the cervical spine in critically injured patients: a comprehensive C-spine protocol to avoid unnecessary delays in diagnosis. Eur Spine J 2006;15:1801–1810 PubMed

5. Tomycz ND, Chew BG, Chang YF, et al. MRI is un­ necessary to clear the cervical spine in obtunded/ comatose trauma patients: the four-year experience of a level I trauma center. J Trauma 2008;64:1258– 1263 PubMed 6. Taylor AS. Fracture dislocation of the cervical spine. Ann Surg 1929;90:321–340 PubMed 7. Harrop JS, Vaccaro A, Przybylski GJ. Acute respiratory compromise associated with flexed cervical traction after C2 fractures. Spine 2001;26:E50–E54 PubMed 8. Cotler JM, Herbison GJ, Nasuti JF, Ditunno JF Jr, An H, Wolff BE. Closed reduction of traumatic cervical spine dislocation using traction weights up to 140 pounds. Spine 1993;18:386–390 PubMed 9. Wimberley DW, Vaccaro AR, Goyal N, et al. Acute quadriplegia following closed traction reduction of a cervical facet dislocation in the setting of ossification of the posterior longitudinal ligament: case report. Spine 2005;30:E433–E438 PubMed



Nonoperative Management of Cervical Spine Trauma

10. Vaccaro AR, Falatyn SP, Flanders AE, Balderston RA, Northrup BE, Cotler JM. Magnetic resonance evaluation of the intervertebral disc, spinal ligaments, and spinal cord before and after closed traction reduction of cervical spine dislocations. Spine 1999;24:1210– 1217 PubMed 11. Grant GA, Mirza SK, Chapman JR, et al. Risk of early closed reduction in cervical spine subluxation injuries. J Neurosurg 1999;90(1, Suppl):13–18 PubMed 12. Miller CP, Bible JE, Jegede KA, Whang PG, Grauer JN. Soft and rigid collars provide similar restriction in cervical range of motion during fifteen activities of daily living. Spine 2010;35:1271–1278 PubMed 13. Evans NR, Hooper G, Edwards R, et al. A 3D motion analysis study comparing the effectiveness of cervical spine orthoses at restricting spinal motion through physiological ranges. Eur Spine J 2013;22(Suppl 1): S10–S15 PubMed 14. Tescher AN, Rindflesch AB, Youdas JW, et al. Rangeof-motion restriction and craniofacial tissue-interface pressure from four cervical collars. J Trauma 2007; 63:1120–1126 PubMed 15. Gavin TM, Carandang G, Havey R, Flanagan P, Ghanayem A, Patwardhan AG. Biomechanical analysis of cervical orthoses in flexion and extension: a comparison of cervical collars and cervical thoracic orthoses. J Rehabil Res Dev 2003;40:527–537 PubMed 16. Ivancic PC. Do cervical collars and cervicothoracic orthoses effectively stabilize the injured cervical spine? A biomechanical investigation. Spine 2013; 38:E767–E774 PubMed 17. Schneider AM, Hipp JA, Nguyen L, Reitman CA. Reduction in head and intervertebral motion provided by 7 contemporary cervical orthoses in 45 individuals. Spine 2007;32:E1–E6 PubMed 18. Sandler AJ, Dvorak J, Humke T, Grob D, Daniels W. The effectiveness of various cervical orthoses. An in vivo comparison of the mechanical stability provided by several widely used models. Spine 1996;21: 1624–1629 PubMed 19. Ackland HM, Cooper DJ, Malham GM, Kossmann T. Factors predicting cervical collar-related decubitus ulceration in major trauma patients. Spine 2007; 32:423–428 PubMed 20. Anderson PA, Budorick TE, Easton KB, Henley MB, Salciccioli GG. Failure of halo vest to prevent in vivo motion in patients with injured cervical spines. Spine 1991;16(10, Suppl):S501–S505 PubMed 21. Lind B, Sihlbom H, Nordwall A. Forces and motions across the neck in patients treated with halo-vest. Spine 1988;13:162–167 PubMed 22. Ebraheim NA, Liu J, Patil V, et al. Evaluation of skull thickness and insertion torque at the halo pin insertion areas in the elderly: a cadaveric study. Spine J 2007;7:689–693 PubMed 23. Rizzolo SJ, Piazza MR, Cotler JM, Hume EL, Cautilli G, O’Neill DK. The effect of torque pressure on halo pin

complication rates. A randomized prospective study. Spine 1993;18:2163–2166 PubMed 24. Vieweg U, Schultheiss R. A review of halo vest treatment of upper cervical spine injuries. Arch Orthop Trauma Surg 2001;121:50–55 PubMed 25. Tashjian RZ, Majercik S, Biffl WL, Palumbo MA, Cioffi WG. Halo-vest immobilization increases early morbidity and mortality in elderly odontoid fractures. J Trauma 2006;60:199–203 PubMed 26. Koller H, Zenner J, Hitzl W, et al. In vivo analysis of atlantoaxial motion in individuals immobilized with the halo thoracic vest or Philadelphia collar. Spine 2009;34:670–679 PubMed 27. Richter D, Latta LL, Milne EL, et al. The stabilizing effects of different orthoses in the intact and unstable upper cervical spine: a cadaver study. J Trauma 2001; 50:848–854 PubMed 28. Polin RS, Szabo T, Bogaev CA, Replogle RE, Jane JA. Nonoperative management of types II and III odontoid fractures: the Philadelphia collar versus the halo vest. Neurosurgery 1996;38:450–456, discussion 456– 457 PubMed 29. Benzel EC, Hadden TA, Saulsbery CM. A comparison of the Minerva and halo jackets for stabilization of the cervical spine. J Neurosurg 1989;70:411–414 PubMed 30. Majercik S, Tashjian RZ, Biffl WL, Harrington DT, Cioffi WG. Halo vest immobilization in the elderly: a death sentence? J Trauma 2005;59:350–356, discussion 356–358 PubMed 31. Fleming BC, Huston DR, Krag MH, Sugihara S. Pin force measurement in a halo-vest orthosis, in vivo. J Biomech 1998;31:647–651 PubMed 32. Fleming BC, Krag MH, Huston DR, Sugihara S. Pin loosening in a halo-vest orthosis: a biomechanical study. Spine 2000;25:1325–1331 PubMed 33. Kim DH, Vaccaro AR, Affonso J, Jenis L, Hilibrand AS, Albert TJ. Early predictive value of supine and upright X-ray films of odontoid fractures treated with halo-­ vest immobilization. Spine J 2008;8:612–618 PubMed 34. Kumar S, Ferrari R, Narayan Y. Looking away from whiplash: effect of head rotation in rear impacts. Spine 2005;30:760–768 PubMed 35. Crawford JR, Khan RJ, Varley GW. Early management and outcome following soft tissue injuries of the neck-a randomised controlled trial. Injury 2004;35: 891–895 PubMed 36. Maddox JJ, Rodriguez-Feo JA III, Maddox GE, Gullung G, McGwin G, Theiss SM. Nonoperative treatment of occipital condyle fractures: an outcomes review of 32 fractures. Spine 2012;37:E964–E968 PubMed 37. Koech F, Ackland HM, Varma DK, Williamson OD, Malham GM. Nonoperative management of type II odontoid fractures in the elderly. Spine 2008;33: 2881–2886 PubMed 38. Molinari WJ III, Molinari RW, Khera OA, Gruhn WL. Functional outcomes, morbidity, mortality, and fracture healing in 58 consecutive patients with geriatric

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Chapter 4 odontoid fracture treated with cervical collar or posterior fusion. Global Spine J 2013;3:21–32 PubMed 39. Vaccaro AR, Madigan L, Bauerle WB, Blescia A, Cotler JM. Early halo immobilization of displaced traumatic spondylolisthesis of the axis. Spine 2002;27:2229– 2233 PubMed 40. Li XF, Dai LY, Lu H, Chen XD. A systematic review of the management of hangman’s fractures. Eur Spine J 2006;15:257–269 PubMed 41. Halliday AL, Henderson BR, Hart BL, Benzel EC. The management of unilateral lateral mass/facet fractures of the subaxial cervical spine: the use of magnetic resonance imaging to predict instability. Spine 1997; 22:2614–2621 PubMed

42. Spector LR, Kim DH, Affonso J, Albert TJ, Hilibrand AS, Vaccaro AR. Use of computed tomography to predict failure of nonoperative treatment of unilateral facet fractures of the cervical spine. Spine 2006;31: 2827–2835 PubMed 43. Syre P III, Rodriguez-Cruz L, Desai R, et al. Civilian gunshot wounds to the atlantoaxial spine: a report of 10 cases treated using a multidisciplinary approach. J Neurosurg Spine 2013;19:759–766 PubMed 44. Medzon R, Rothenhaus T, Bono CM, Grindlinger G, Rathlev NK. Stability of cervical spine fractures after gunshot wounds to the head and neck. Spine 2005; 30:2274–2279 PubMed

5 Occipital Condyle Fractures and Occipitocervical Dissociation Philipp Schleicher, Matti Scholz, and Frank Kandziora

■■ Introduction Injuries of the craniovertebral junction comprise occipital condyle fractures (OCFs) and atlanto-occipital dissociation (AOD). The latter entity is also frequently termed occipitocervical dissociation, craniocervical dissociation, and craniocervical dislocation in the literature. The relevance of both OCF and AOD has increased in recent decades for several reasons. Improved prehospital trauma care has increased the survival rate of patients with AOD, so that they are now treated in the emergency department; in the past this injury was nearly 100% fatal. Furthermore, the wide implementation of computed tomography (CT) scanning as the primary imaging modality in trauma patients has improved the detection rate of AOD as well as that of OCF, which also has a much higher incidence rate than during the X-ray era. Especially for AOD, due to its inherent risk for severe neurologic damage or fatal outcome, immediate diagnosis and adequate treatment are crucial. Despite the increasing relevance of OCF and AOD, the evidence class of the existing data still does not exceed class IV (case series), because the incidence of these injuries, although increasing, is still very low.

Nevertheless, with an increasing number of cases published in the literature, it is pos­ sible to extract some recommendations for the diagnosis and treatment of these types of injuries.

■■ Epidemiological Features and Pathomechanisms The exact epidemiological occurrence of AOD is unknown, because the literature encompasses only case reports and case series. As of 2014, we found a total of 534 reported cases of AOD in the Medline database, with about a third of cases (n = 182) having survived at least several days after the injury. The largest case series included 69 patients (with seven survivors, yielding a 10% survival rate). The largest survival series reported on 33 patients AOD, 23 of whom survived (70% survival rate). Recent prospective studies revealed a very low incidence of AOD in a Western trauma population. Müller et al found only five AODs in 2,162 trauma patients receiving a cervical spine CT scan, for an incidence of 0.23%.1 Of these five patients, three died within 1 week after injury. In contrast, ­AOD can be found in up to 18% of trauma fatalities.2 Thus, these data



50

Chapter 5 indicate that AOD is a rare but severe injury, with a short-term mortality of about 60%. Occipital condyle fractures have been reported in at least 393 cases as of 2014. The largest case series consisted of 107 patients. The reported incidence varies greatly, depending on the underlying population of these case series. Maserati et al found ~ 200 OCFs in a population of ~ 25,000 trauma patients who were admitted to their level I trauma center, yielding an incidence of ~ 0.8%.3 A similar OCF incidence (1.1%) was found in 700 trauma patients treated in a level I trauma center intensive care unit (ICU) was reported by Krüger et al.4 The mortality of OCFs is difficult to determine, because there are very few reports on fatal outcome in the literature. In one of the largest case series by Maserati et al, the mortality was 12%. A major cause of death was a concomitant traumatic brain injury (TBI).3 Additionally, the incidence of OCF in trauma fatalities is very similar to that in surviving trauma patients (1–4%). This implies that OCF is not in itself a fatal injury, but rather that the occasional death of a patient with OCF might mainly be due to concomitant injuries such as TBI. In the majority of cases, a motor vehicle ­accident (MVA) is the injury mechanism. This ­explains why the typical OCF patient is a young man (average age in the early 30s); the male/ female ratio is 2:1. In contrast, the typical ­AOD patient is much younger; 20% of all cases are reported in children. This is often explained by the shallower occipitoatlantal joint surfaces, higher head moment, and laxer ligaments in children.

■■ Anatomic Features and

Biomechanics

The clinician must be cognizant of several anatomic features of the craniocervical junction. To assess the neurologic symptoms, it is important to know the exact location of the exiting cranial nerves around the occipital condyles. To determine the instability of a fracture, thor-

ough knowledge of the craniocervical ligaments and their bony attachments is helpful.

Joints and Ligaments at the Craniocervical Junction The occipitoatlantal joint complex consists mainly of two convex-shaped occipital condyles at the anterior rim of the foramen magnum and the corresponding concave-shaped upper joint surfaces of the atlas. The joint’s surface topology, which was described as “somewhat cuplike” by White and Panjabi,5 makes it act as a roller joint, with 25 degrees of flexion/ extension and 5 degrees of axial rotation and lateral bending. This joint is called a “yes joint” because it is used when the head is nodding “yes.” The ligamentous stability of the craniovertebral junction is provided mostly by the internal ligaments around the spinal canal. From anterior to posterior, the following structures are involved: • The apical odontoid ligament connects the tip of the odontoid with the anterior rim of the foramen magnum. • The paired alar ligaments connect the tip of the odontoid with either the anteromedial border of the occipital condyle or the anteromedial portion of the atlantal lateral mass. The account for 30% of the rotational stability of the C0-C1 joint and may cause an avulsion fracture of the occipital condyle. • The longitudinal part of the cruciate ligament connects the posterior vertebral body of the axis vertebra to the foramen magnum. • The tectorial membrane runs from the anterior foramen magnum downward and continues to the strong posterior longitudinal ligament. Its main function is the limitation of hyperextension. • The outer ligament system consists of the external anterior and posterior atlanto-occipital membrane, the joint capsules of the C0-C1 joint, and the nuchal ligament.



Occipital Condyle Fractures and Occipitocervical Dissociation

The Lower Cranial Nerves and Their Exits In and around the occipital condyles, there are two bony canals that serve as an exit route for various structures, mostly nerves. In these narrow canals, the nerves and vessels are in danger of being damaged by direct trauma or indirect compression due to swelling, bleeding, or scar tissue developing even months after an injury. Directly within the hypoglossal canal, the hypoglossal nerve exits the skull base and runs to the tongue. It is the only structure running through this canal. Slightly lateral of the occipital condyle, the jugular foramen is passed by the glossopharyngeal, vagal, and accessory nerves as well as the internal jugular vein and posterior meningeal artery. Behind the occipital condyles, an emissary vein connects the sigmoid sinus and a vertebral venous plexus through the posterior condylar canal.

■■ Diagnosis Clinical Presentation The clinical presentation of AOD and OCF shows great variability in symptom type and in the timing of symptom occurrence. In rare cases, these entities are diagnosed after an asymptomatic interval of several months!6–8 Due to the severity of the injury, patients who survive an AOD are often unconscious and show signs of brain or spinal cord injury (SCI). In OCF, transient or persistent loss of consciousness is reported in 80% of cases. Sudden cardiac arrest in a patient with blunt head trauma, especially during transfer and manipulation, should raise the suspicion for brainstem compression due to craniocervical instability. In OCF, involvement of the lower cranial nerves occurs in 30% of cases. Therefore, given the above findings, it is important for clinicians to know the function of

the relevant nerves, because lower cranial nerve palsy might be the major symptom leading to the diagnosis. In about a third of patients, the cranial nerve palsies might develop after several months as a sequela of craniocervical trauma. Delayed neurologic impairment may result from fragment migration or the compressive effect of developing fibrous tissue around the narrow nerve canals. If the patient is conscious, the careful examiner should also look for one of the following signs and symptoms: • Tenderness in the posterior craniocervical transition is reported in nearly every patient with OCF, and it seems to be a sensitive symptom. In Theodore et al’s9 report on 64 patients, only four did not report upper cervical tenderness, and all four were either intoxicated or had severe facial or extremity injury. • Dysphagia is an often-reported symptom in delayed diagnosis. It is caused either by glossopharyngeus, vagal, or hypoglossus nerve palsy or, in very rare cases, by the development of a retropharyngeal pseudomeningocele.10–12 • Hoarseness and numbness in the anterior part of the ear as well as in the external auditory canal (R. auricularis) are further signs of a vagal nerve lesion. • Torticollis or weakness in lifting the shoulder or abduction of the arm is seen when the accessory nerve is damaged, because it innervates the sternocleidomastoid and the trapezius muscle. • A deviation of the tongue indicates a lesion of the ipsilateral hypoglossal nerve.

Imaging Blunt head trauma has a significant association with cervical spine injuries, including the upper cervical spine. With the improved preclinical treatment algorithms, the survival rate of trauma victims with AOD is increasing. But these patients might die in the emergency department if a diagnosis

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Chapter 5 of AOD is missed or delayed. Thus, it is essential to use a set of diagnostic measures of very high sensitivity. Several methods to correctly recognize this severe injury have been developed; they are of varied practicability. Their sensitivity and specificity have been evaluated in large studies. X-ray imaging is a less reliable method because of its poorer visualization of specific bony landmarks. Additionally, these landmarks are quite distant from the origin of the occipitoatlantal joint. Therefore, only grossly displaced lesions will be recognized by on X-ray. Nowadays, with the widespread availability of CT scanners in the trauma setting, CT-based methods are preferable. The available methods are as follows: • The Wholey basion–dens interval (sensitivity 61%, specificity 71%; Fig. 5.1) served as a standard measure for many years because of its easy application. A line is drawn from the tip of the basion to the tip of the odontoid process. A value of more than 10 mm in adults and 12 mm in infants is considered abnormal. A value of more than 16 mm

Fig. 5.1  Wholey’s basion (B)–dens (D) interval. (From Gire JD, Roberto RF, Bobinski M, Klineberg EO, Durbin-Johnson B. The utility and accuracy of computed tomography in the diagnosis of occipitocervical dissociation. Spine J 2013;13:510–519. Reproduced with permission.)

is associated with a significantly increased mortality.13 • The Harris basion-axis interval (sensitivity 28.5%, specificity 84.5%) describes the distance from the basion to a tangent drawn through the posterior wall of C2. Normal range is –4 to 12 mm in adults and 0 to 12 mm in children.14 • The Powers ratio (sensitivity 32%, specificity 78%) is the ratio of the distance from the basion to the C1 posterior arch divided by the distance from the opisthion to the anterior C1 arch. A ratio greater than 1 is considered pathological. This method yields false-negative results when there are strictly longitudinal or posterior dislocations.15 • Lee’s X-line method (sensitivity 54%, specificity 38%) is similar to the Powers ratio, with a line drawn from the basion to the spinolaminar line of C2 and another line drawn from the opisthion to the posterior inferior edge of the C2 vertebral body. The lines should touch the tip of the dens or the highest edge of the C1 spinolaminar line, respectively. Otherwise, an AOD is likely.16 • For Sun’s interspinous ratio (sensitivity 28.5%, specificity 77%), the interspinous distance between C1-2 and C2-3 is measured. If the ratio is greater than 2.5, AOD can be assumed.17 • The Dublin method measures the distance between the mandible and the anterior arch of the atlas and the odontoid, respectively, which should not exceed 2 and 10 mm. This method is strongly dependent on proper positioning and an intact mandible, and it has proven to be imprecise.18 • Using CT scans, Pang et al19 developed the condyle–C1 interval (CCI), which is based on 16 measured parameters in different planes, which makes it difficult to use in everyday practice. It was simplified by Gire et al20 to the revised CCI (sensitivity 100%, specificity 92%; Fig. 5.2), in which the joint surface distance in the midsagittal plane at the point of greatest separation between the occipital condyle and the C1 lateral mass is measured. A value greater than 2.5 mm is considered pathological. A derivative of this measurement is the condylar sum, which is



Occipital Condyle Fractures and Occipitocervical Dissociation the most critical step in the diagnostic process, and it should be done if the results of the CT leave the clinician in doubt about the diagnosis (Figs. 5.1 and 5.2).

Classification Due to the rarity of the lesion, there are not many classification systems for AOD. One of the oldest is the classification published by Traynelis et al21 in 1986 (Fig. 5.3). They classified the injury according to the vector of translation as follows: type I, anterior; type II, axial; and type III, posterior. The distribution of these types is reported as follows: type I, 40%; type II, 40%; and type III, 5%. The remaining 15% are not classifiable. Although Fig. 5.2  Revised condyle–C1 interval (CCI). OC, often applied, this classification is criticized beoccipital condyle. (From Gire JD, Roberto RF, cause in true AOD, the severe instability makes Bobinski M, Klineberg EO, Durbin-Johnson B. The a dislocation in every direction likely, and the utility and accuracy of computed tomography in the dislocation seen on X-ray is no more than a diagnosis of occipitocervical dissociation. Spine J snapshot in time; the situation may immedi2013;13:510–519. Reproduced with permission.) ately change. Furthermore, this classification has no implications in determining the approthe sum of the left and right revised CCI and priate therapy, as all of these injuries have an urgent need for surgical stabilization. should not exceed 5 mm. Horn et al22 proposed a different approach, • For OCF, the sensitivity of conventional which takes into account different grades of X-rays is low. Recent studies found a sensiabnormal findings in CT and MRI, and helps tivity of between 0 and 3%. Occasionally, a determine the appropriate therapy. The auretropharyngeal hematoma can be a sign on thors differentiate two grades AOD. Grade I the lateral view, but this is very unspecific. lesions have normal findings on CT and only Thus, conventional X-ray is not helpful in moderately abnormal findings on MRI. These imaging these types of injuries. injuries are regarded as stable and can be One major criticism of both X-ray and CT treated conservatively in a hard cervical collar. scans is that a spontaneous reduction of the Grade II lesions have abnormal findings on CT severely unstable AOD may present false-­ and grossly abnormal findings on MRI. These negative finding, leading to the catastrophic lesions should be quickly stabilized surgically. consequences of a missed diagnosis. Therefore, There are other classification systems for some authors recommend magnetic resonance OCFs. One of the earliest was introduced by imaging (MRI) for all cases that are doubtful on Saternus in 1987,23 summarizing his experience CT. On MRI, the theoretically proposed criteria with autopsy studies of traffic fatalities. He difare integrity of the cruciate ligament and the ferentiated six types of condylar fracture: occipitocervical (OC) joint capsule, and fluid enrichment on the pericondylar area as a sign • Axial compression for intracapsular hematoma (see Fig. 5.5c, • Axial traction below). However, none of these criteria has • Rotation with axial strain proven to be an indicator of a true instability. • Oblique-compression Therefore, with the wide availability of CT, • Oblique-traction the decision of whether to request an MRI is • Transverse thrust

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a

b

c

Fig. 5.3a–c  Traynelis classification for atlanto-­ occipital dislocation. (a) anterior translation. (b) posterior translation. (c) longitudinal translation. The red arrows indicate the direction of translation.

(From Kandziora F, Schnake K, Hoffmann R. [Injuries to the upper cervical spine. Part 2: osseous injuries]. Unfallchirurg 2010;113:1023–1039, quiz 1040. Reproduced with permission.)

Anderson and Montesano (Fig. 5.4) in­ troduced their classification system in 1988, based on only six patients.24 It is easy to apply and it helps determine the appropriate treatment, so it has gained widespread use. The ­authors differentiate three different types of OCF:

Jeanneret has added a fourth type, a ring-shaped avulsion of the entire foramen magnum.25 The second most often used classification is that of Tuli et al8 published in 1997, based on a retrospective review of 93 of their own cases. They differentiate nondisplaced (type I), displaced but stable (type IIA), and displaced and unstable (type IIB). Patients are determined to be unstable if they have one of the following criteria:

• Type I: impressions fracture • Type II: skull base fracture that extends into the occipital condyle • Type III: avulsion fracture of the alar ligament, likely to be displaced (Fig. 5.5a,b).

a

b

Fig. 5.4a–c  Anderson and Montesano classification for occipital condyle fractures. (a) Type I injuries are compression fractures of the occipital condyle. (b) Type II injuries are skull base fractrues extending into the occipital condyle. (c) Type II injuries are

1. > 8 degrees of axial rotation of the occiput– C1 joint to one side

c

avulsion injuries at the attachment of the alar ligaments. (From Kandziora F, Schnake K, Hoffmann R. [Injuries to the upper cervical spine. Part 2: osseous injuries]. Unfallchirurg 2010;113:1023–1039, quiz 1040. Reproduced with permission.)



Occipital Condyle Fractures and Occipitocervical Dissociation

a

b

c

Fig. 5.5a–e  Case example of a young man who was injured in a high-speed motor vehicle accident (MVA). (a) Computed tomography (CT) scan shows a subluxation of the right OC joint (red arrow) and an avulsion fracture of the left occipital condyle (Anderson and Montesano type III). (b) A rotatory displacement of the occiput against the atlas can be

seen. Note the left occipital condyle fracture (Anderson and Montesano type III). (c) Magnetic resonance imaging (MRI) demonstrates fluid enhancement of the OC joint capsule and widening of the joint space, which constitutes an atlanto-­ occipital dislocation according to the CCI rule. (continued on page 56)

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Chapter 5

d

e

Fig. 5.5a–e (continued )  (d) CT holographic image following treatment with an occipitocervical fusion. The C2 screws are placed as Magerl screws, adding high stability to the C1-C2 joint as well as facilitating

better fusion. (e) Twelve-month follow-up CT scans. Note the reduced and nearly fused OC joint and the bony bridge along the occipital plate.

2. > 1 mm of occiput–C1 translation 3. > 7 mm of overhang of C1 on C2 4. > 45 degrees of axial rotation of C1–C2 to one side 5. > 4 mm of C1–C2 translation 6. < 13 mm between the posterior body of C2 and the posterior ring of C1 7. Avulsed transverse ligament 8. Evidence of ligamentous disruption on MRI

None of the above classification systems have undergone validity testing (Figs. 5.3 and 5.4).

■■ Treatment Treatment options for the craniocervical junction include conservative therapy with immo-



Occipital Condyle Fractures and Occipitocervical Dissociation

bilization in a hard cervical collar or in a halo jacket, and operative therapy with occipitocervical fusion via a posterior midline approach (Fig. 5.5d,e). Another option is direct trans­ articular screw osteosynthesis of C0-C1. Due to very unstable nature of AOD with the risk of severe neurologic deficits, operative stabilization is the treatment of choice in most cases. Reviews have found a neurologic deterioration in 27% of patients who were treated with external stabilization alone. In contrast, there was only one case found with neurologic deterioration after surgical intervention. To prevent a fatal dislocation on the way to the operating room, some authors recommend applying a halo device as soon as possible, although this cannot completely prevent the craniovertebral junction from displacing.6–10,26 Therefore, most authors recommend a definitive open procedure as soon as possible. When reducing an AOD, some authors have observed a worsening of neurologic function if axial traction was applied. Van de Pol et al26 found that 10% of patients experienced neurologic worsening under traction, so if traction is necessary for reduction, they apply it with great caution.

Conservative Treatment Conservative treatment for OCF is suitable for Anderson and Montesano types I and II and Tuli types I and IIA. A rigid cervical collar (e.g., Philadelphia collar) should be worn for at least 6 weeks. For AOD, there is only one situation that is suitable for conservative treatment in a cervical collar: a Horn grade I lesion10–12,22 in which there are subtle changes seen on MRI without any abnormality seen on CT. All other lesions require open stabilization. If this is impossible, then immobilization in a halo device should be performed. For definitive treatment in a halo, one should consider the complication rate associated with this procedure, which is a high as 30% in some studies, and includes pin loosening and infection.

Surgical Options In case of severe instability, which is the case in nearly all AODs and in Anderson and Montesano type III and Tuli IIB OCFs, stabilization and fusion of the OC joint complex is indicated. This is especially valid for AOD, because Bellabarba et al27 have found that neurologic damage may occur in up to 29% of patients between the time of injury and stabilization. The standard procedure in this situation is an occipitocervical fusion, using a screw/rod system connected to an occipital plate. The ­instrumentation may include the C2 vertebra, because the rupture of the cruciate ligament, which attaches to the C2 vertebra, might cause atlantoaxial instability as well. In severe posttraumatic pain or gross displacement with compression of cranial nerves, an OC joint resection followed by a fusion procedure is also possible. In hypoglossal nerve palsy due to a compressing fragment, decompression of the hypoglossal canal might be indicated either as a sole procedure or as part of a fusion procedure. However, the success rates of this procedure are low.

Technical Recommendations The standard occipitocervical fusion from C0 to C2 or even lower leads to 50% loss of motion of the axial rotation and of a high proportion of flexion/extension in the cervical spine, which has a significant effect on patient comfort in activities of daily living. Therefore, this pos­ sibility should be specifically included in the informed consent. Perioperatively, the patient should be positioned with a slightly flexed position in the OC joint, so the patient will be able to look at the floor several meters in front of him for better comfort. An upward directed view should be avoided, which has been reported to be extremely uncomfortable. To avoid excessive motion loss, some alternative options are possible: • In cases of bony avulsions, which usually show a good healing capability, a temporary stabilization is performed, followed by early implant removal 3 to 9 months after the

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Chapter 5

•

•

•

•

initial operation. Prior to implant removal, a solid healing of the fragment should be demonstrated on CT. If the atlantoaxial motion segment is found to be stable, an occipitoatlantal fusion either by direct transarticular screw placement14,28,29 or by a C1–lateral mass screw and occipital plate construct15,30 is possible, preserving at least the rotational motion of the C1-C2 joint complex. For direct transarticular screw placement, the screw trajectory is ~ 45 degrees upward, strictly parallel to the sagittal plane. The entry point is the midpoint in the atlantal lateral mass at the junction with the posterior arch. The recommended screw dimensions are 4 mm in diameter and 30 mm in length. Extreme care should be taken to assess the hypoglossal canal anatomy prior to surgery, because this structure is at high risk during this procedure. The construct might be reinforced by a posterior iliac crest bone graft similar to a Brooks fusion for promoting bony fusion.16,29 The screw trajectories for C1 or C2 screws in a screw-and-rod construct shall be based on the common techniques for screw placement in these vertebrae (e.g., Goel/Harms technique, translaminar screws, pars screw placement). When placing the occipital plate, care should be taken to place the plate directly in the midline between the superior and inferior nuchal line, because here the occipital bone shows the greatest thickness and there is no risk of injuring the venous sinuses. The screws should be placed bicortically. Major cerebrospinal fluid (CSF) leakage through the drill holes is avoided by placing the screw quickly.

Due to the severity of AOD, the outcome reports mainly focus on survival and neurologic outcome. (Survival rates were cited earlier; see Epidemiological Features and Pathomechanisms, above.) Horn et al22 report in their series of 33 patients an outcome of 10 deaths (30%), four tetraplegic patients (12%), two paraplegic patients (6%), two hemiparetic patients (6%), and 14 patients without any neurologic deficit (42%). Bellabarba et al27 reported their outcomes based on the American Spinal Injury Association (ASIA) impairment scale, with similar results in 17 patients: 47% ASIA E, 39% ASIA D, 12% ASIA C, and 12% ASIA A. Results concerning postop­erative pain or social rehabilitation are not provided. Maserati et al3 found posttreatment neck pain in only 2% of their 97 patients with OCF. A delayed instability requiring surgical stabilization was found in only 1% of their patients. Maddox et al31 evaluated the Neck Disability Index score of 32 patients after conservative treatment of OCFs. He found mild disability or none in 14 patients (44%). Severe disability was found in four patients (12.5%). Interestingly, Anderson and Montesano grade I and II injuries showed worse results than Anderson and Montesano III injuries. Hanson et al32 found “good recovery,” defined as being independent of nursing care after 1 month, in 32 of 35 patients (91%) who sustained OCF without a concomitant TBI. In the same series, 30 of 85 surviving patients (35%) had a “poor outcome” after 1 month, still requiring continuous nursing support, tube feeding, or tracheostomy. These results are predominantly due to the TBI. Data on posttraumatic pain were not reported.

■■ Chapter Summary ■■ Prognosis and Outcome As mentioned above, AOD and OCF are injuries of very different severity and therefore they have different outcomes.

The evidence for the diagnosis and treatment of AOD and OCF is low and does not exceed level IV (case series) because of the low incidence of these lesions, which are found in 1% of all trauma victims.



Occipital Condyle Fractures and Occipitocervical Dissociation

Both types of injuries are usually suffered by patients in high-speed MVAs. The typical patient with an OCF is a 30-year-old man, whereas the typical patient with an AOD is a child. An AOD is a potentially fatal injury, with an estimated mortality of 50 to 60%. The rate of neurologic damage including TBI and SCI is high; these injuries are the major determinants of long-term outcome. In contrast, an OCF is a more benign injury with a lower mortality and more favorable outcome. When not accompanied by severe TBI or cranial nerve deficit, posttraumatic pain is the major, albeit infrequent, problem. Delayed diagnosis of both entities is a common occurrence. The typical symptoms that lead to the diagnosis are lower cranial nerve palsies or dysphagia and persistent neck pain. The diagnosis can be made based on CT scan findings in nearly 100% of the cases. In cases of uncertain findings, the addition of an MRI can be useful. Conventional X-ray is insufficient for both entities. Atlanto-occipital dislocation is treated with immediate stabilization in a halo device, followed by a definitive open occipitocervical stabilization as soon as possible. Most OCFs can be treated conservatively in a hard cervical collar, but the lack of treatment will lead to an unfavorable outcome of this usually benign lesion.

Pearls ◆◆ The incidence of OCF and AOD is increasing. ◆◆ Both injuries are likely to be missed due to their

rarity and poor visualization on conventional X-rays. ◆◆ Atlanto-occipital dislocation is an injury of high mortality; thus, immediate diagnosis and treatment is crucial for a good outcome. ◆◆ An OCF can be treated in a hard cervical collar in the majority of cases. ◆◆ Standard treatment for unstable lesions is an occipitocervical fusion from C0 to C2 or lower. Pitfalls ◆◆ Do not rely on conventional X-rays for patients

◆◆

◆◆

◆◆

◆◆

◆◆

injured in high-speed MVAs. CT is the gold standard for diagnosis of AOD or OCF. Any doubt should trigger an MRI, because bony structures may be randomly reduced to a physiological position during the initial CT scan. Although conservative treatment is reasonable for most OCFs, no treatment at all will lead to an unfavorable outcome. For operative treatment, positioning should be performed with extreme care not to further harm the spinal cord and brainstem. In occipitocervical fusion, positioning should create a slightly flexed position of the OC joint for increased patient comfort. During follow-up in conservative treatment of OCFs, look for delayed development of cranial nerve lesions.

References

Five Must-Read References 1. Mueller FJ, Kinner B, Rosskopf M, Neumann C, Nerlich M, Fuechtmeier B. Incidence and outcome of atlanto-occipital dissociation at a level 1 trauma centre: a prospective study of five cases within 5 years. Eur Spine J 2012;22:65–71 2. Lador R, Ben-Galim PJ, Weiner BK, Hipp JA. The association of occipitocervical dissociation and death as a result of blunt trauma. Spine J 2010;10:1128–1132   3. Maserati MB, Stephens B, Zohny Z, et al. Occipital condyle fractures: clinical decision rule and surgical management. J Neurosurg Spine 2009;11:388–395 PubMed 4. Krüger A, Kühne C, Oberkircher L, Ruchholtz S, Frangen T, Junge A. Fractures of the occipital condyle clinical spectrum and course in eight patients. J Craniovertebr Junction Spine 2013;4:50

5. White AA, Panjabi MM. Clinical Biomechanics of the Spine. Philadelphia: Lippincott Williams & Wilkins; 1990 6. Demisch S, Lindner A, Beck R, Zierz S. The forgotten condyle: delayed hypoglossal nerve palsy caused by fracture of the occipital condyle. Clin Neurol Neurosurg 1998;100:44–45 PubMed 7. Schliack H, Schaefer P. [Hypoglossal and accessory nerve paralysis in a fracture of the occipital condyle]. Nervenarzt 1965;36:362–364 PubMed   8. Tuli S, Tator CH, Fehlings MG, Mackay M. Occipital condyle fractures. Neurosurgery 1997;41:368–376, discussion 376–377 PubMed 9. Theodore N, Aarabi B, Dhall SS, et al. Occipital condyle fractures. Neurosurgery 2013;72(Suppl 2):106– 113 PubMed

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Chapter 5 10. Naso WB, Cure J, Cuddy BG. Retropharyngeal pseudomeningocele after atlanto-occipital dislocation: report of two cases. Neurosurgery 1997;40:1288– 1290, discussion 1290–1291 PubMed 11. Reed CM, Campbell SE, Beall DP, Bui JS, Stefko RM. Atlanto-occipital dislocation with traumatic pseudomeningocele formation and post-traumatic syringomyelia. Spine 2005;30:E128–E133 PubMed 12. Choi EH, Jun AY, Choi EH, Shin KY, Cho AR. Traumatic atlanto-occipital dislocation presenting with Dysphagia as the chief complaint: a case report. Ann Rehabil Med 2013;37:438–442 PubMed 13. Wholey MH, Bruwer AJ, Baker HL Jr. The lateral roentgenogram of the neck; with comments on the atlanto-odontoid-basion relationship. Radiology 1958;71:350–356 PubMed 14. Harris JHJ Jr, Carson GC, Wagner LK, Kerr N. Radiologic diagnosis of traumatic occipitovertebral dissociation: 2. Comparison of three methods of detecting occipitovertebral relationships on lateral radiographs of supine subjects. AJR Am J Roentgenol 1994;162: 887–892 PubMed 15. Powers B, Miller MD, Kramer RS, Martinez S, Gehweiler JAJ Jr. Traumatic anterior atlanto-occipital dislocation. Neurosurgery 1979;4:12–17 PubMed 16. Lee C, Woodring JH, Goldstein SJ, Daniel TL, Young AB, Tibbs PA. Evaluation of traumatic atlantooccipital dislocations. AJNR Am J Neuroradiol 1987;8:19–26 PubMed 17. Sun PP, Poffenbarger GJ, Durham S, Zimmerman RA. Spectrum of occipitoatlantoaxial injury in young children. J Neurosurg 2000;93(1, Suppl):28–39 PubMed 18. Dublin AB, Marks WM, Weinstock D, Newton TH. Traumatic dislocation of the atlanto-occipital articulation (AOA) with short-term survival. With a radiographic method of measuring the AOA. J Neurosurg 1980;52:541–546 PubMed 19. Pang D, Nemzek WR, Zovickian J. Atlanto-occipital dislocation—part 2: The clinical use of (occipital) condyle-C1 interval, comparison with other diagnostic methods, and the manifestation, management, and outcome of atlanto-occipital dislocation in children. Neurosurgery 2007;61:995–1015, discussion 1015 PubMed 20. Gire JD, Roberto RF, Bobinski M, Klineberg EO, Durbin-Johnson B. The utility and accuracy of computed tomography in the diagnosis of occipitocervical dissociation. Spine J 2013;13:510–519 PubMed

21. Traynelis VC, Marano GD, Dunker RO, Kaufman HH. Traumatic atlanto-occipital dislocation. Case report. J Neurosurg 1986;65:863–870 PubMed 22. Horn EM, Feiz-Erfan I, Lekovic GP, Dickman CA, Sonntag VKH, Theodore N. Survivors of occipitoatlantal dislocation injuries: imaging and clinical correlates. J Neurosurg Spine 2007;6:113–120 PubMed 23. Saternus KS. Bruchformen des Condylus occipitalis. Z Rechtsmed. 1987;99:95–108 24. Anderson PA, Montesano PX. Morphology and treatment of occipital condyle fractures. Spine 1988;13: 731–736. 25. Jeanneret B (1994) Obere Halswirbelsäule. In: Witt AN, Rettig H, Schlegel KF (Hrsg). Spezielle Orthopädie Wirbelsäule-Thorax-Becken. Stuttgart: Thieme, S 3.1– 3.37 26. van de Pol GJ, Hanlo PW, Oner FC, Castelein RM. Redislocation in a halo vest of an atlanto-occipital dislocation in a child: recommendations for treatment. Spine 2005;30:E424–E428 PubMed 27. Bellabarba C, Mirza SK, West GA, et al. Diagnosis and treatment of craniocervical dislocation in a series of 17 consecutive survivors during an 8-year period. J Neurosurg Spine 2006;4:429–440 PubMed 28. Grob D. Transarticular screw fixation for atlanto-occipital dislocation. Spine 2001;26:703–707 PubMed 29. Feiz-Erfan I, Gonzalez LF, Dickman CA. Atlantooccipital transarticular screw fixation for the treatment of traumatic occipitoatlantal dislocation. Technical note. J Neurosurg Spine 2005;2:381–385 PubMed 30. Anderson AJ, Towns GM, Chiverton N. Traumatic occipitocervical disruption: a new technique for stabilisation. Case report and literature review. J Bone Joint Surg Br 2006;88:1464–1468 PubMed 31. Maddox JJ, Rodriguez-Feo JA III, Maddox GE, Gullung G, McGwin G, Theiss SM. Nonoperative treatment of occipital condyle fractures: an outcomes review of 32 fractures. Spine 2012;37:E964–E968 PubMed 32. Hanson JA, Deliganis AV, Baxter AB, et al. Radiologic and clinical spectrum of occipital condyle fractures: retrospective review of 107 consecutive fractures in 95 patients. AJR Am J Roentgenol 2002;178:1261– 1268 PubMed

6 Atlas Injuries Matti Scholz, Philipp Schleicher, and Frank Kandziora

■■ Introduction After fractures of the odontoid process, atlas fractures represent the second most common type of bony lesion in the upper cervical spine, predominantly caused by axial compression forces. Fractures of the atlas account for 2 to 13% of cervical spine injuries and 1 to 3% of spine fractures. These fractures occur more frequently with increasing age. If the fracture is isolated, it can be treated conservatively. But it is important to determine if there are additional fractures of the cervical spine, such as an odontoid fracture, which may be present in 50% of patients with atlas fractures. In these cases it is the concomitant fracture that determines the treatment strategy.1An isolated traumatic lesion of the transverse ligament is a rare entity, but it may cause a persistent atlantoaxial instability requiring atlantoaxial fusion. A fracture of the first cervical vertebra was first described by Sir Astley Cooper, in an autopsy report in 1823. A century later, Sir Geoffrey Jefferson developed an initial classification system of atlas fractures by evaluating 42 cases in the literature and four of his own cases. Jefferson was the first to describe a four-part burst fracture after vertical compression of the atlas, which became known as the Jefferson fracture. Barker et al2 in 1976 were the first to

describe a bony avulsion of the transverse atlantal ligament (TAL) as an uncommon fracture entity entailing a fracture of the medial wall of the lateral mass of C1. As the fracture mechanism was unknown, the authors postulated that “the bone fragment is produced by a combination of TAL stretching and pressure on the lateral mass due to contraction of the neck muscles.” Twenty years later, Dickman et al3 evaluated lesions of the TAL and assessed their relevance in determining whether to treat the patient with surgical stabilization of the potentially unstable atlas fracture. Several reviews have addressed the diagnosis and treatment of atlas fractures.4,5 However, due to a lack of randomized studies, only class IV evidence is available to establish treatment recommendations for this rare fracture entity.

■■ Clinical Presentation Patients suffering from a traumatic fracture of the atlas present with complaints about pain in the upper cervical spine, headache, and difficulty with cervical spine rotation. A neurologic deficit linked to an atlas fracture is rare.6 However, a traumatic lesion to the lower four cranial nerves (IX to XII), known as the Collet-­



62

Chapter 6 Sicard syndrome, was described by Domenicucci et al.7 Furthermore, due to a potential unilateral or bilateral vertebral artery lesion or posttraumatic thrombosis, symptoms associated with a hypoperfusion of the basilar supply territory can include nausea, vomiting, tinnitus, impaired vision, or drop attacks.

■■ Classification There are several classification systems for atlas fractures. The first classification was based on the findings of Jefferson in 1920. He categorized atlas fractures into three types: type I, a bilateral fracture of the anterior or posterior ring; type 2, a combined anterior and posterior ring (four-part) burst fracture; and type 3, a fracture of the lateral mass. A more recently established classification system is that of Gehweiler et al,8 who categorized these fractures into five types (Fig. 6.1): Type 1: a rare isolated fracture of the anterior arch of the atlas predominantly with two fracture lines. Hyperextension forces and strain of the longus colli muscle creates a typical bilateral fracture at the anterior atlas ring close to the area of longus colli muscle origin. Type 2: an isolated, predominantly bilateral, fracture of the posterior atlas ring caused by hyperextension forces, resulting in a compression of the posterior arch of the atlas

between the occiput and the posterior arch of the axis. Type 3: a combined injury of the anterior and posterior arch of the atlas, the so-called Jefferson fracture. This type is further subdivided into stable and unstable injuries. Type 3a: a stable injury in which the TAL is intact. Type 3b: an unstable injury in which there is a severe lateral displacement of a lateral mass, suggesting a lesion of the transverse ligament.9 Type 4: a fracture caused by axial compression forces and involving a predominantly unilateral mass. Type 5: an extremely rare isolated fracture of the C1 transverse process, generally caused by a direct trauma, such as a punch. If the patient presents with an unstable atlas injury (Gehweiler’s type 3b), it is important to determine the type of transverse ligament lesion using the Dickman3classification (Fig. 6.2). Dickman distinguishes between an intraligamentous rupture and a bony avulsion of the ligament. The intraligamentous rupture (type 1) can be further categorized as a central lesion (type 1a) oras a lesion close to the lateral mass (type 1b). The bony avulsion of the transverse ligament from a lateral mass (type 2) can be further categorized as an isolated bony avulsion (type 2a) or as a bony avulsion due to a fracture of the lateral mass (type 2b). These fractures are Gehweiler’s type 4. The degree of dislocation of the bony fragment is important in determining the surgical treatment.

Fig. 6.1  Gehweiler classification of atlas fractures.8



Atlas Injuries Fig. 6.2  Dickman classification of transverse ligament lesions.3

■■ Imaging and Criteria for

Instability

On conventional cervical spine radiograms, non­ displaced atlas fractures are often overlooked. In case of an atlas burst fracture with severe dislocation, the open-mouth anteroposterior (AP) or odontoid view can show a uni- or bilateral overhang of a C1 lateral mass (Fig. 6.2) over a C2 superior articular process. In the case of a C1 overhang, the distance between the lateral border of C1 and the lateral border of C2 should be measured. If the dislocation is bi­lateral, both sides should be measured and summed. Accordingly to the “rule of Spence,” instability is diagnosed if the overhang of C1 is more than 6.9 to 8.1 mm. An additional criterion for instability is the widening of the anterior atlantodental interval to more than 3 mm. Both measures suggest a failure of the transverse ligament, which is the strongest stabilizing structure for the atlantoaxial joint. To evaluate the integrity of the atlas ring in detail and to classify an atlas fracture, computed tomography (CT) is recommended. Axial CT slices should be carefully reviewed to determine the presence of a bony avulsion of the transverse ligament as a criterion for a potential instability. If a dislocation of the C1 lateral mass is seen and CT was unable to detect a bony avulsion of the transverse ligament, then

magnetic resonance imaging (MRI) is recommended to evaluate the integrity of the transverse ligament10and to distinguish between stable burst fractures (Gehweiler type 3a) and unstable burst fractures (Gehweiler type 3b). Fractures of the upper cervical spine can compromise vascular structures. However, the vertebral artery is most at risk, especially in Gehweiler type 5 lesions. In these rare cases, CT angiography or MRI angiography should be performed to exclude lesions of the vertebral artery within the foramen of the transverse process of C1.11

■■ Therapy Algorithm

(Fig. 6.3)

Gehweiler Type 1, 2, and 5 Fractures Atlas fractures of types 1, 2, and 5 are stable. These fractures can be treated with cervical spine immobilization with a soft cervical collar for 6 weeks.

Gehweiler Type 4 Fractures Most type 4 fractures are minimally displaced and can be treated conservatively in a soft cer-

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Fig. 6.3  The authors’ preferred treatment algorithm for management of atlas fractures.

vical collar. In the rare case of a primary or secondary significant dislocation of the fractured lateral mass, resulting in incongruence of the atlanto-occipital and atlantoaxial joint, a reduction under traction and retention for 6 to 12 weeks in a halofixator is recommended. Axial traction in most cases leads to an adequate lateral mass realignment by ligamentotaxis, and adequate bony healing can be achieved. However, after the initial reduction and after 6 and 12 weeks under halotraction, evaluation with a CT scan is necessary to confirm an adequate joint realignment and bony healing. In case of inadequate initial reduction under halotraction, resulting in a symptomatic nonunion, surgery is indicated to relieve the patient of persistent pain caused by posttraumatic arthritis of the destructed joints. Due to the potential challenges in achieving a good screw fixation within the fractured lateral mass of C1, which also affects the atlantoaxial and a ­ tlanto-occipital joint, an occipitocervical fusion is the treatment of choice in most cases. However, osteoarthritis in displaced type 4 fractures is a slow process. Therefore, the treatment algorithm should be modified in elderly patients. To avoid complications of halotraction in elderly patients,12 treatment in a stiff collar instead of a halofixa-

tor, even in cases of displaced type 4 atlas fractures, can be considered.

Gehweiler Type 3 Fractures In stable atlas type 3a fractures, conservative therapy in a Philadelphia collar is possible. However, these patients should be carefully reviewed regarding further dislocation, nonunion, and signs for atlantoaxial instability. For unstable type 3b fractures with minimally displaced bony avulsion of the transverse ligament, direct osteosynthesis of the atlas or halotraction for 6 to 12 weeks is recommended. However, more surgeons now prefer the surgical management of type 3b lesion, because halo traction entails potential patient discomfort, a higher complication rate, and a higher nonunion rate. An isolated atlas osteosynthesis is not recommended in elderly patients, due to their reduced capability for bony healing,or in type 3b fractures with severe dislocated bony avulsion of the transverse ligament (Dickman type 2). Although temporary fixation of the atlantoaxial complex is a possible alternative in young patients, a definitive atlantoaxial fusion is the treatment of choice for elderly patients suffering from unstable atlas type 3b fractures.



Atlas Injuries

For displaced type 3b atlas fractures and intraligamentous rupture (Dickman type 1), an atlantoaxial fusion is recommended due tothe unlikelihood of ligamentous healing and the potential for posttraumatic translational atlantoaxial instability. Depending on the patient’s anatomy and the feasibility of intraoperative reduction, a posterior atlantoaxial fusion using the Magerl/Gallie or Goel/Harms technique is a viable treatment option.

■■ Conservative Management

of Unstable Atlas Fractures

Most patients with stable atlas fractures do well with conservative treatment. There are only small case series available that address the successful conservative management of unstable atlas burst fractures. However, some authors of recent reviews advocate 6 to 12 weeks of halo-fixator traction to manage these unstable atlas fractures, predominantly Dickman type 2 lesions. The advantage of halotraction is the external stabilization it provides without the need for surgery, which entails potential complications.13 Another advantage is the avoidance of atlantoaxial fusion, which was predominantly performed before the introduction of isolated atlas osteosynthesis. However, halo­traction is an invasive form of conservative fracture management, and thus it is not without risks. Complications of halotraction are documented by Strohm et al,14 who evaluated halo-­fixator treatment in 41 patients with upper cervical spine fractures. They reported several complications: screw loosening (15%), pin-screw infection (10%), skin necrosis (5%), fracture redislocation (20%), and intracranial screw penetration after a fall in one patient (2.5%). Furthermore, the patients were asked to rate the comfort of the halotraction; 58% rated it as intolerable, 32% used a rating in the middle of the continuum, and only 10% rated it as tolerable. Due to the discomfort and potential complication of halo-vest treatment and the availability of modern operative techniques, we prefer the surgical management of unstable

atlas fractures, except for displaced Gehweiler type 4 fractures. In these cases, especially in young patients, the morbidity of atlanto-oc­ cipital fixation/fusion is avoided by adequate reduction and halo-vest treatment.

■■ Operative Management Isolated Osteosynthesis of the Atlas Indications The primary indication for an isolated osteosynthesis is an unstable burst fracture of the atlas (Gehweiler type 3b) with bony avulsion of the transverse ligament (Dickman type 2). An illustrative case is shown in Fig. 6.4. The bony dislocation should be mild if a good fragment reposition and later bony healing of the ligament avulsion are to be achieved, to prevent the complication of posttraumatic insufficiency of the transverse ligament with chronic pain due to translational atlantoaxial instability. For the same reason, an unstable atlas fracture with an intraligamentous transverse ligament lesion should not be treated with an osteosynthesis of the atlas. In cases of Gehweiler type 3b and Dickman type 1 lesions, it is impossible to achieve ligamentous healing because bony structures will consolidate. This might lead secondarily to translational atlantoaxial instability, which has to be treated as well by an atlantoaxial fusion.

Biomechanics Koller et al15 performed in vitro biomechanical testing to analyze the mechanical property of a C1 osteosynthesis with incompetency of the transverse atlantal ligament. Five specimens (C0–C2) with an intact C1-ring and an intact transverse ligament were tested regarding their atlantoaxial subluxation and load displacement. After a bony osteotomy (simulating a Jefferson fracture), a unilateral left capsulotomy, a cut of the transverse ligament, and a C1 osteosynthesis, the specimens were tested again. The

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a

b

c

d

e

Fig. 6.4a–e  Case example of a 59-years old patient with an unstable atlas fracture, Gehweiler type 3b, and bony avulsion of the transverse atlantal ligament, Dickman type 2. (a) Open-mouth lateral X-ray with overhang of the right lateral mass. (b) Postoperative lateral and open-mouth radio-

grams. (c) Computed tomography (CT) shows moderate ligament bone avulsion. (d) Three months postoperative CT with adequate C1 ring restoration. (e) Six months postoperative CT shows bony healing of C1 ring and osseous integration of ligament bone avulsion.

authors found sufficient biomechanical C1–C2 stability under physiological loads after a C1 osteosynthesis and concluded that “C1 osteosynthesis might be a valid alternative for the treatment of displaced Jefferson burst fractures in comparison to fusion of C1-2.” Bicortical lateral mass screws are highly recommended because their pullout strength is significantly higher than that of monocortical C1 lateral mass screws.16 Ma et al17 compared the pullout resistance of C1 pedicle screws and C1 lateral mass screws biomechanically in vitro. They found equal pullout resistance with monocortical C1 pedicle screws and bicortical C1 lateral mass screws, but they recommended monocortical screw placement in case of C1 pedicle screw usage because of potential lower morbidity.

Surgical Procedure

.

a

b

An osteosynthesis of the atlas can be performed by an anterior-transoral, an isolated posterior, or a combined posterior/anterior-­ transoral approach (Fig. 6.5). For each approach, only small-series case reports are available (Table 6.1). After a standard posterior midline approach to the upper cervical spine, C1 lateral mass screws are placed in order to perform a posterior atlas osteosynthesis. The dorsal root ganglion of C2 and venous plexus are carefully mobilized and caudally retracted to identify the midpoint of the inferior lateral mass at the junction with the posterior arch, which is an ideal entry point for lateral mass screws. The drilling trajectory is determined by the

c

Fig. 6.5a–c  Different treatment strategies for isolated atlas osteosynthesis. (a) Transoral anterior fixation. (b) Posterior fixation. (c) Combined posterior and anterior fixation.



Atlas Injuries

Table 6.1  Case Reports Describing the Different Approaches to Atlas Osteosynthesis Author Ma W et

Approach/ Implant al.28

Patients/ Follow-Up

Transoral screws + plate

20 patients/ 6 months

Sun SH et al.29

Transoral screws + plate

Hu Y et al.30

Transoral screws + plate

Ruf M et al.31

Transoral polyaxial screws + rod

8 patients/ 6–24 months 1 patient/ 6 months 6 patients/ 6.5 years

Abeloos L et al.32

Posterior polyaxial screws + rod Posterior polyaxial screws + plate

1 patient/ 7 months 22 patients/ 2–32 months

Posterior polyaxial screws + rod Posterior polyaxial screws + rod

12 patients/ 22 months 3 patients/ 14 months

Combined polyaxial screw + rod + transoral wiring

8 patients/ 38 months

He B et al.33 Hu Y et al.26 Bransford R et al.34

Böhm H et al.22

anatomy of the lateral mass and the fracture lines, whichmust be carefully analyzed prior to surgery.18 Atlas repositioning is the key point of the osteosynthesis, and it is achieved either by using dedicated reposition tools or manually by bilateral external neck compression. The reduction is then fixed with the screw-and-rod connection. The anterior transoral atlas osteosynthesis is performed by a standard transoral approach. Transorally inserted screws should be placed in the “safe zone.” Detailed anatomic studies of these ideal entry points are available in the literature.19 The combined posterior-anterior C1 fixation uses a posterior screw fixation with longer bicortical C1 lateral mass screws and additional transoral wiring between the screw tips to close the gap within the anterior arch of C1. This combined procedure enables a perfect C1-

Outcome Bony fusion in all 20 patients after 6 months, no instability, no complications Bony fusion in all 8 patients, no postoperative complications Bony fusion,no instability C1/2, physiological C1/2 rotation No approach-related complications, one screw-and-rod dislocation with re-dislocation of lateral mass and worst clinical outcome (Dennis pain score 4) Bony fusion, normal physiological C1/2 rotation Bony fusion in all 22 patients, no complications, normal physiological range of motion

One died after 14 days (associated injuries); bony fusion in the other 2 patients, normal physiological rotation One delayed union after anterior revision, no approach-related complications; all 8 patients had bony fusion at final follow-up

ring reduction. However, due to the increased risk of using two approaches, this procedure should not be the treatment of first choice. Only one case report is available describing this combined approach (Table 6.1).

Potential Complications Retracting the venous plexus and C2 root ganglion often causes venous bleeding. Significant venous bleeding is rare, and it can be treated with local soft compression or insertion of thrombin-soaked Gelfoam. If the bleeding does not stop, the insertion of a commercially available gelatin-thrombin preparation might help. Injuries of the vertebral artery are rare, but might occur because of the drilling and screw insertion with lateral trajectory or due to the use of repositioning tools for an indirect C1ring compression. A lesion of the posterior C2

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Chapter 6 root ganglion is possible due to retraction pressure, and bipolar coagulation should be used in cases of venous bleeding. However, these lesions are predominantly benign and do not entail clinical impairment. The main complication is an incomplete reduction with later nonunion and slowly developing atlantoaxial instability or atlantoaxial/atlanto-occipital arthritis. Wound infections are infrequent but they can be life threatening, especially after transoral procedures.

analyze the achieved reduction. If an adequate repositioning of the anterior ring is impossible using the posterior approach, an additional anterior transoral approach is an option to achieve a full reconstruction of the C1 ring.22 Therefore, if an isolated posterior osteosynthesis is planned, the possibility of having to use an additional transoral approach should be part of the informed consent.

Posterior Atlantoaxial Fusion

Tips and Tricks

Indications

We prefer the isolated posterior approach due to its lower morbidity compared with the transoral and combined approach. Bleeding of the C2 venous plexus can be reduced by consequent exposure close to the C1 arch. If diffuse bleeding occurs, avoid bipolar coagulation. It is better to apply gentle compression with Gelfoam and to start with preparation of the opposite side. An alternative is transpedicular screw insertion. However, an adequate pedicle diameter and careful preparation with protection of vertebral artery are mandatory, if surgeons consider using this technique.20,21 To perform a safe and adequate repositioning of the C1ring, detailed anatomic knowledge about the fracture morphology and about the exact location of the vertebral artery is of prime importance. Due to the necessity of adequate reduction and especially the realignment of the transverse ligament bony fragment, good intraoperative visualization is of great importance. Intraoperative CT or three-dimensional (3D) fluoroscopy is highly recommended to

A posterior atlanto-axial fusion is indicated in cases of unstable atlas burst fractures with ­intraligamentous lesion of the transverse ligament (Dickman type 1). Another indication is the onset of translational atlantoaxial in­ stability after conservative management of Dickman type 2 lesions or failed isolated atlas osteosynthesis.23

a

The Harms and Magerl Surgical Techniques To perform a posterior C1–C2 fusion, two established surgical techniques are available. One option is the Magerl transarticular C1–C2 screw fixation with an additional posterior support using an iliac crest bone graft and wiring as performed by Gallie. The other option is the Harms posterior screw and rod fixation (Fig. 6.6). The technical details of these procedures are beyond the scope of this chapter. The major advantages and disadvantages of these procedures are listed in Table 6.2.

b

Fig. 6.6a,b  Posterior atlantoaxial fusion. (a) Magerl/Gallie technique. (b) Goel-Harms technique.



Atlas Injuries

Table 6.2  Advantages, Disadvantages, and Typical Complications of Magerl/Gallie Procedure Versus Harms Procedure for C1/2 Fixation Transarticular fixation according to Magerl/Gallie

Screw and rod fixation according to Harms

Advantages

•  3 point fixation with adequate biomechanical stability •  Implants are cheap

Disadvantages

•  Requires reposition before screw channel preparation •  3 point fixation is impossible in case of bilateral posterior arch fracture •  Technically demanding •  Lesion of the atlantoaxial joint unfavourable for implant removal in case of temporarily fixation •  Bone graft harvesting mandatory •  Screw trajectory sometimes impossible due to individual anatomy (high riding vertebral artery, obese patients with short neck.) •  Lesion of Vertebral artery (5%) by wrong drilling trajectory an/or high riding artery •  Inadequate screw purchase in C1 lateral mass in case of inadequate reposition

•  Reposition after screw placement possible •  No harm to the C1/2 joint and therefore ideal for temporarily fixation of C1-2 •  Modifications in case of anatomical need possible (e.g. short isthmus screw, lamina screw) •  Implants are expensive •  Technically demanding •  Pedicle screw insertion sometimes impossible (high riding vertebral artery)

Typical complications

Tips and Tricks Magerl Procedure After drilling the first screw hole, the drill should remain in situ. Otherwise, drilling of the second hole may cause a rotation between the atlas and the axis. Then it might be impossible to realign C1 and C2 while inserting the first screw. In cases of lateral or rotational lateral mass displacement, the Magerl screw might miss the C1 lateral mass. Therefore, adequate C1 repositioning has to be verified by AP and lateral intraoperative imaging prior to transarticular drilling. Even with a unilateral “high-riding” vertebral artery, a Magerl screw can be used. However, in these cases the screw has to be placed very steeply. The screw must leave the axis pedicle before entering the isthmus area, and

•  Lesion of Vertebral artery by wrong drilling trajectory •  Venous bleeding C2 plexus •  Lesion C2 root ganglion

should reenter the posterior area of the atlas lateral mass. When using this technique, care must be taken not to use screws that are too long, to avoid a violation of the atlanto-occipital joint. A Gallie wire can be replaced by nonabsorbable thread, which is easier to handle than stiff wires. In cases of bilateral posterior arch fracture, it is impossible to achieve an adequate posterior Gallie fixation. In these cases, a spinal fusion can be achieved by direct placement of autologous bone in the posterior dorsal part of the lateral atlantoaxial joints. However, without adequate three-point fixation, the Magerl fixation is less stable than a Harms construct. Therefore, we prefer the Harms technique for treatment of unstable four-part Jefferson fractures (Gehweiler type 3b) and intraligamentous disruption of the TAL (Dickman type 1).

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Harms Technique The specific choice of screw length facilitates intraoperative repositioning. If atlas repositioning in the posterior direction is necessary, the screw heads in C1 should be more ventral than those in C2. The repositioning is performed by a screw-and-rod connection in C2 first. The rod is then located posterior to the C1 screw head, which can be easily elevated by pulling the screw head using the repositioning tool. In cases of a bilateral posterior arch fracture, it is impossible to fixate an iliac crest between the posterior arch and the C2 spinous process for posterior fusion. In these cases, a spinal ­fusion can be achieved by direct introduction of autologous bone in the posterior dorsal part of the lateral atlantoaxial joints. If the patient’s anatomy prevents using a transpedicular screw in C2, short isthmus screws or lamina screws are an alternative for screw fixation in C2.

of neck pain, as shown on the Visual Analogue Scale (initial scores of 7.52 ± 3.2; postoperative scores of 1.80 ± 2.12), and a postoperative cervical range of motion in the normal physiological range was also reported. The atlantoaxial rotation, as measured by functional CT, was 62 degrees on average (range, 36–75 degrees). These findings were similar to the clinical results of several other authors (Table 6.1). Patients with atlantoaxial fusion also do well, but head rotation is reduced due to C1/2 fusion. Elliott et al27 compared the outcome of trans­ articular screws (Magerl procedure) and screw-­ and-rod constructs (Goel/Harms procedure) for C1/2 fusion. A higher incidence of vertebral artery injury (4% vs 2.0%), a higher rate of screw malposition (7.1% vs 2.4%), and a slightly lower fusion rate were evident with the use of translaminar screws.

■■ Chapter Summary ■■ Outcome As previously stated, most patients with stable atlas fractures do well with conservative treatment. But conservative treatment of Jefferson fractures does not mean that patients will return to their preinjury physical condition. Dvorak et al24reported a poorer long-term outcome (as assessed by Short Form 36 and by a painscore) for patients with displaced Jefferson fractures greater than 7 mm (Gehweiler type 3b) compared with minor displaced Jefferson fractures (Gehweiler type 3a). Lewkonia et al25 performed a literature review addressing the outcome of conservative management in cases of C1 burst fractures. They found that 8 to 20% of patients complain about stiffness in the neck, 14 to 80% of patients experience mild pain, and a 34% of patients report limitations in their activities. There are only case reports with a maximum of 22 patients available in the literature, describing the outcome after surgical management of unstable atlas fractures. Hu et al26 treated 12 patients with isolated posterior C1 osteosynthesis. Patients reported good relief

Atlas fractures are the result of compression or hyperextension forces. These fractures are often combined with fractures of the axis and especially the odontoid process. The Gehweiler classification of atlas injuries requires CT imaging. To distinguish between stable and unstable atlas injury, it is necessary to evaluate the integrity of the transverse atlantal ligament on MRI and to use the Dickman classification of the potential lesion. Most atlas fractures are stable and can be successfully managed by immobilization in a soft or hard collar. Unstable atlas fractures may be managed conservatively by halofixation, but more surgeons now prefer surgical treatment due to the potential discomfort of halo traction. Atlas fractures with ligamentous disruption of the transverse atlantal ligament or severe dislocation of bony ligament avulsion should be treated by C1/2 fusion. Unstable atlas fractures with moderate dislocation of bony ligament avulsion may be treated by atlas osteosynthesis. There is little evidence supporting the different treatment strategies of atlas fractures. Few studies are available comparing conser-



Atlas Injuries

vative and operative management of unstable atlas fractures or comparing the different operative treatment strategies.

Pitfalls ◆◆ In cases of an atlas fracture, patients should be

carefully examined for concomitant fractures.

Pearls ◆◆ Modern imaging facilitates the diagnosis of

transverse atlantal ligament lesions.

◆◆ By combining the Gehweiler and Dickman classi-

fication systems, the stability of an atlas fracture can be predicted. ◆◆ Modern osteosynthesis techniques for unstable atlas fractures enable a safe atlas fusion with preservation of C1/2 motion. ◆◆ For atlantoaxial fusion,the standard Goel-Harms and Magerl techniques provide fixation for the C1-C2 segment.

◆◆ Before considering conservative therapy for a

Gehweiler type 3 lesion, care should be taken to determine if a transverse ligament lesion is also present. ◆◆ It is impossible to perform a Magerl/Gallie fusion in cases of inadequate pre- and intraoperative reduction. ◆◆ Do not overlook a high-riding vertebral artery if a Harms procedure or C2 pedicle screw is planned. ◆◆ Patients in halotraction should be regularly examined for pin and halo-vest complications.

References

Five Must-Read References 1. Li-Jun L, Ying-Chao H, Ming-Jie Y, Jie P, Jun T, DongSheng Z. Biomechanical analysis of the longitudinal ligament of upper cervical spine in maintaining atlantoaxial stability. Spinal Cord 2014;52:342–347 PubMed 2. Barker EGJ Jr, Krumpelman J, Long JM. Isolated fracture of the medial portion of the lateral mass of the atlas: a previously undescribed entity. AJR Am J Roentgenol 1976;126:1053–1058 PubMed 3. Dickman CA, Greene KA, Sonntag VK. Injuries involving the transverse atlantal ligament: classification and treatment guidelines based upon experience with 39 injuries. Neurosurgery 1996;38:44–50 PubMed  4. Joaquim AF, Ghizoni E, Tedeschi H, et al. Upper cervical injuries—a rational approach to guide surgical management. J Spinal Cord Med 2014;37:139–151 PubMed  5. Syre P, Petrov D, Malhotra NR. Management of upper cervical spine injuries: a review. J Neurosurg Sci 2013;57:219–240 PubMed 6. Dettling SD, Morscher MA, Masin JS, Adamczyk MJ. Cranial nerve IX and X impairment after a sports-­ related Jefferson (C1) fracture in a 16-year-old male: a case report. J Pediatr Orthop 2013;33:e23–e27 PubMed 7. Domenicucci M, Mancarella C, Dugoni ED, Ciappetta  P, Paolo M. Post-traumatic Collet-Sicard syndrome: personal observation and review of the pertinent literature with clinical, radiologic and anatomic considerations. Eur Spine J 2014 Aug 24. [Epub ahead of print] PubMed 8. Gehweiler JA, Osborne RL, Becker RF. The Radiology of Vertebral Trauma. Philadelphia: WB Saunders; 1980

9. Kandziora F, Schnake K, Hoffmann R. [Injuries to the upper cervical spine. Part 2: osseous injuries]. Unfallchirurg 2010;113:1023–1039, quiz 1040 PubMed 10. Dickman CAC, Mamourian A, Sonntag VKV, Drayer BPB. Magnetic resonance imaging of the transverse atlantal ligament for the evaluation of atlantoaxial instability. J Neurosurg 1991;75:221–227 PubMed 11. Hagedorn JCII, Emery SE, France JC, Daffner SD. Does CT angiography matter for patients with cervical spine injuries? J Bone Joint Surg Am 2014;96: 951–955 PubMed 12. Daentzer D, Flörkemeier T. Conservative treatment of upper cervical spine injuries with the halo vest: an appropriate option for all patients independent of their age? J Neurosurg Spine 2009;10:543–550 PubMed 13. Longo UG, Denaro L, Campi S, Maffulli N, Denaro V. Upper cervical spine injuries: indications and limits of the conservative management in Halo vest. A systematic review of efficacy and safety. Injury 2010; 41:1127–1135 PubMed 14. Strohm PC, Müller ChA, Köstler W, Reising K, Südkamp NP. [Halo-fixator vest—indications and complications]. Zentralbl Chir 2007;132:54–59 PubMed 15. Koller H, Resch H, Tauber M, et al. A biomechanical rationale for C1-ring osteosynthesis as treatment for displaced Jefferson burst fractures with incompetency of the transverse atlantal ligament. Eur Spine J 2010;19:1288–1298 PubMed 16. Eck JC, Walker MP, Currier BL, Chen Q, Yaszemski MJ, An K-N. Biomechanical comparison of unicortical versus bicortical C1 lateral mass screw fixation. J Spinal Disord Tech 2007;20:505–508 PubMed

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Chapter 6 17. Ma X-Y, Yin QS, Wu Z-H, et al. C1 pedicle screws versus C1 lateral mass screws: comparisons of pullout strengths and biomechanical stabilities. Spine 2009; 34:371–377 PubMed 18. Sonntag VKH. Lateral mass screw fixation of the atlas: importance of anatomy of C1 for lateral mass screw placement. World Neurosurg 2010;74:270– 271 PubMed 19. Kandziora F, Schulze-Stahl N, Khodadadyan-Klostermann C, Schröder R, Mittlmeier T. Screw placement in transoral atlantoaxial plate systems: an anatomical study. J Neurosurg 2001;95(1, Suppl):80–87 PubMed 20. Tan M, Dong L, Wang W, et al. Clinical application of the “pedicle exposure technique” for atlantoaxial instability patients with a narrow C1 posterior arch. J Spinal Disord Tech 2015;28:25–30 PubMed 21. Qian L-X, Hao D-J, He B-R, Jiang Y-H. Morphology of the atlas pedicle revisited: a morphometric CT-based study on 120 patients. Eur Spine J 2013;22:1142– 1146 PubMed 22. Böhm H, Kayser R, El Saghir H, Heyde CE. [Direct osteosynthesis of instable Gehweiler type III atlas fractures. Presentation of a dorsoventral osteosynthesis

of instable atlas fractures while maintaining function]. Unfallchirurg 2006;109:754–760 PubMed 23. Jacobson ME, Khan SN, An HS. C1-C2 posterior fixation: indications, technique, and results. Orthop Clin North Am 2012;43:11–18, vii PubMed 24. Dvorak MF, Johnson MG, Boyd M, Johnson G, Kwon BK, Fisher CG. Long-term health-related quality of life outcomes following Jefferson-type burst fractures of the atlas. J Neurosurg Spine 2005;2:411–417 PubMed 25. Lewkonia P, Dipaola C, Schouten R, Noonan V, Dvorak M, Fisher C. An evidence-based medicine process to determine outcomes after cervical spine trauma: what surgeons should be telling their patients. Spine 2012;37:E1140–E1147 PubMed 26. Hu Y, Xu R-M, Albert TJ, et al. Function-preserving reduction and fixation of unstable Jefferson fractures using a C1 posterior limited construct. J Spinal Disord Tech 2014;27:E219–E225 PubMed 27. Elliott RE, Tanweer O, Boah A, et al. Outcome comparison of atlantoaxial fusion with transarticular screws and screw-rod constructs: meta-analysis and review of literature. J Spinal Disord Tech 2014;27: 11–28 PubMed

7 Odontoid Fractures, Hangman’s Fractures, and C2 Body Fractures Wilco C. Peul and Carmen L.A. Vleggeert-Lankamp

■■ Odontoid Fractures Odontoid fractures account for 9 to 18% of all cervical spine fractures and are most frequently caused by either hyperextension or hyperflexion. In the elderly, odontoid fractures are the most common cervical spine fractures.1 Moreover, as the population ages, these fractures will be seen more often in clinical practice. Fractures of the odontoid process occur in different forms requiring different treatments. Anderson and D’Alonzo2 proposed the use of the following classification system for odontoid fractures, which is still commonly used today: type I, fracture of the tip of the odontoid process; type II, fracture of the neck of the odontoid process; and type III, a fracture that runs through the body of C2. Type I odontoid fractures need no surgical stabilization. A rigid collar is sufficient to enable the ligaments to heal. Type II and type III fractures can be treated either conservatively or surgically. A type III fracture is generally treated by external immobilization if the fracture surface is large enough to allow spontaneous healing. If dislocation is likely to take place, a surgical intervention is often proposed. Deciding on surgical or conservative treatment for patients with fractures of the odontoid process is based on the following factors: fracture pattern, patient age, neurologic deficits, and the patient’s medical condition.3 Surgical

intervention is in most cases performed by anterior odontoid screw fixation (one or two screws) or posterior atlantoaxial arthrodesis. Conservative management of type II and III fractures involves rigid (e.g., halo vest, Minerva cast) or nonrigid (e.g., cervical collar, cervicothoracic orthosis) immobilization. The optimal treatment of odontoid fractures in elderly patients is still a subject of controversy, as this age group typically has a higher risk of developing complications when treated surgically, such as nonunion, than when treated conservatively.4–7 Consequently, many factors must be taken into account to find the right balance between fracture healing and treatment complications.

Anterior Screw Fixation Direct anterior screw fixation provides immediate stabilization of the spine and preserves upper cervical spine mobility. However, not all types of odontoid fractures are suitable for this approach. To adequately report on the fracture line in a type II dens fracture, Grauer et al8 adjusted the Anderson and d’Alonzo classification (Fig. 7.1). Type II and type III odontoid fractures are less suitable for anterior screw fixation if the fracture line is oriented obliquely from anterior-­ inferior to posterior-superior (type IIC). However, if the fracture line is oriented otherwise



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Chapter 7

Fig. 7.1  Anderson and d’Alonzo classification as adapted by Grauer et al.8 (Reproduced with permission.)

(type IIA or type IIB), the patient is appropriate for an anterior screw fixation. A pooled meta-analysis of nonunion, reoperation, infection, and approach-related complications after anterior odontoid screw fixation was recently published.9 A total of 63 studies were included. The authors found a pooled nonunion rate of 10% and a reoperation rate of 5% (including malposition of screws). Complications included infection in 0.2%, dysphagia in 10%, and hoarseness in 1.2%. A multivariate meta-analysis demonstrated a higher rate of nonunion in patients over 70 years of age. Apfelbaum et al10 demonstrated an overall bone fusion rate of 88% in type II dens fractures treated with an anterior dens screw, but a significantly lower rate of bone fusion (25%) in patients with late fractures (> 6 months after injury). It can be concluded that direct anterior screw fixation is an effective and safe method for treating recent odontoid fractures in patients younger than 70 years of age. Unfortunately, none of the studies correlated nonunion with the well-being of the patient.

Surgical Versus Nonsurgical Treatment of Type II Fractures A recent systematic review of papers published between 1975 and 2011 summarized the outcome of surgical and conservative interventions for type II and III odontoid fractures in the ­elderly, focusing primarily on clinical outcome and secondarily on fracture union and stability rates.1 A total of 17 studies were identified that met the inclusion criteria. They were all retrospective studies. (Not included was a more recent prospective multicenter study that provided data on this same topic.5) Only two of the 17 studies compared the clinical outcomes of surgery with those of conservative treatment. One was a retrospective study of 27 patients over 70 years of age, which found less morbidity in the surgery group (statistically significant; p = 0.037), but no statistically significant difference in nonunion at the fracture site (p = 0.64) except for type II fractures (p = 0.0063).11 The other study (n = 17) found a slightly better clinical outcome in surgically compared with



Odontoid Fractures, Hangman’s Fractures, and C2 Body Fractures

conservatively treated patients (average Smiley-­ Webster [SW] score 1.25 and 1.92, respectively; 1 is excellent, 4 is poor). Statistical analysis of these results could not be performed due to the limited number of patients involved.12 In five studies evaluating the clinical outcome using the SW score, both surgically and conservatively treated patients had an intermediate outcome. The average SW score was 1.71 for surgically treated patients and 2.02 for conservatively treated patients. Of 16 studies reporting extractable union rates, four compared surgery with conservative treatment. Union was achieved in 85% (29/34) of the surgically treated patients and in 44% (16/36) of the conservatively treated patients. The results were mainly based on X-ray findings. In the individual studies, no statistical analysis could be performed due to the small number of patients. In a comparison of all patients included in the 16 studies, union was achieved in 81% (218/269) of surgically treated patients and 44% (56/128) of conservatively treated patients. Again, in the individual studies no statistical analysis could be performed. All 17 studies reported extractable stability rates, showing fracture stability in most patients regardless of their treatment (dynamic X-ray). In a comparison of all patients included in the 17 studies, stability was achieved in 95% (245/258) of surgically treated patients and in  87% (94/108) of conservatively treated patients. In five studies comparing surgically to conservatively treated patients, stability was achieved in 97% (35/36) and 77% (36/47) of cases, respectively.

Prospective Study There was one recent prospective multicenter study comparing outcomes and complications of nonsurgical and surgical treatment of type II odontoid fractures in patients 65 years of age or older.5 A total of 159 patients with a type II dens fracture were enrolled; 101 patients were treated surgically, and 58 patients were treated nonsurgically, as determined by the treatment preferences of the treating physicians and the patients. The two groups were similar with regard to baseline characteristics. The most com-

mon surgical treatment was posterior C1-C2 arthrodesis (79%), whereas the most common nonsurgical treatment was immobilization with the use of a hard collar (81%). The overall mortality rate was 18% over the 12-month follow-up period; it was slightly higher in the nonsurgical group. This is a likely outcome because the patients who are in poor clinical condition are not subjected to a surgical intervention a priori. At 12 months, the Neck Disability Index (NDI) score had decreased by 14.7 points (out of 50) in the nonsurgical cohort, which was significantly more than the NDI decrease of 5.7 points in the surgical group. The surgical group had a significantly lower rate of nonunion (5% versus 21% in the nonsurgical group; p = 0.0033). Fracture stability was not evaluated. There was no difference in the overall rate of complications.

Discussion The review data were insufficient to determine the difference on clinical outcome between surgical and conservative interventions in the elderly with isolated odontoid fractures. Overall, it seems that the reported differences lack clinical relevance. The prospective study claims that surgical treatment can be beneficial for the patient’s general well-being (measured by NDI). But it is not unlikely that the better NDI state of the surgically treated patients is due to their condition, which is generally better at baseline than is the condition of the patients who are treated conservatively. Overall, it can be concluded that it is safe to surgically treat elderly patients with type II odontoid fractures who are healthy enough for general anesthesia. Surgically treated patients appear to show higher osseous union rates compared with conservatively treated patients, but this does not lead to higher stability rates in the surgically treated patients. Moreover, the union and stability rates were never correlated with the patients’ general well-being and their reports of neck pain. The outcomes that are reported are highly dependent on the clinician’s choice of the initial treatment. Prospective studies focusing primarily on the correlation between clinical outcome and fracture union/stability

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Chapter 7 are necessary to determine the optimal treatment in the elderly. Moreover, the safety of surgical interventions for odontoid fractures in patients over 80 years old should be evaluated separately.

■■ Biomechanical Studies Anterior Screw Fixation There is still controversy regarding whether one- or two-screw fixation is more appropriate. In a cadaver study, seven axes were treated with one-screw and seven with two-screw fixation. Shear and torsional stiffness were measured using a nondestructive low-load test in six directions before and after transverse osteotomy at the base of the odontoid. Mean stiffness in all directions after screw fixation was similar in both groups. The stiffness after oneand two-screw fixation was not restored to normal; the mean shear stiffness restored ratio was less than 50%, and the mean torsional stiffness restored ratio was less than 6% in both groups. Bone marrow density did not correlate with mean stiffness after screw fixation in both groups.13 It is concluded that one screw is sufficient to perform an anterior odontoid fixation.

Posterior Screw Fixation There are several procedures to fixate the C1-C2 complex. In cadaver studies, the pullout strength of the most commonly described screw techniques are compared: C1 lateral mass to C2 pedicle screw fixation, C1 lateral mass to C2 isthmus screw fixation, C1 to C2 transarticular screw fixation, C1 lateral mass to C2 transarticular screw fixation, and crossed laminar (intralaminar) screw fixation. In general, surgeons choose the technique they are most familiar with, but sometimes the strongest construct is required. Biomechanical studies demonstrate that pedicle screw fixation is in general more resistant to pullout than are other screws. A pedicle screw is not always the safest choice. An in vitro study using human cadaveric spine compared the biomechanical stability of ped-

icle screws with that of various established posterior atlantoaxial fixations used to manage atlantoaxial instability. Seven human cadaveric cervical spines with the occiput attached (C0-C3) had the neutral zone (NZ) and range of motion (ROM) evaluated in three modes of loading.14 The following techniques were compared: C1 lateral mass and C2 short pedicle screw fixation (14- to 16-mm screw), C1 lateral mass and C2 long pedicle screw fixation, C1 lateral mass and C2 intralaminar screw fixation, Sonntag’s modified Gallie fixation, and C1-C2 transarticular screw fixation with posterior wiring. The C1-C2 transarticular group allowed the most lateral bending, and Sonntag’s modified Gallie fixation was significantly weaker and allowed more movement than the other groups. The following conclusion were drawn: the C1-C2 transarticular procedure with wiring provided the highest stability; the modified Gallie method alone was not adequate for atlantoaxial arthrodesis, because it does not provide sufficient stability in lateral bending and rotation modes; and the C2 pedicle screw and C2 intralaminar techniques were biomechanically less stable than the transarticular screw fixation with wiring. Thus, it can be concluded that in general a transarticular screw fixation of C1-C2 with wiring is the most stable construct, directly followed by a C1 lateral mass–C2 pedicle screw fixation, to which the use of a short pedicle screw is considered a good alternative.

■■ C2 Anatomy in Children Computed tomography (CT) plays a central role in the diagnosis of cervical spine fractures. In children, radiolucent synchondroses between ossification centers can resemble fractures. However, when the C2 fractures, it is most likely to fracture at the junctions that were former synchondroses. Recognition of cervical spine fractures in children requires familiarity with normal developmental anatomy and common variants as they appear on CT scans. In a study by Piatt and Grissom,15 841 CT scans of the atlas and axis of children were



Odontoid Fractures, Hangman’s Fractures, and C2 Body Fractures

Fig. 7.2  Bar graph showing the incorporation of the apical ossification center into the dentate process. By “incorporation” we mean the disappearance of

the apical center as a distinct process or nodule. Numbers of Percent of observations at each age are presented.15

­ xamined. Synchondroses were graded as rae diolucent, not totally radiolucent but still visible, or no longer visible. Their locations and symmetries were noted. The presence or absence of the tubercles of the transverse ligament was noted as well. It was observed that the three common ossification centers of the atlas arose in the paired neural arches and the anterior arch, but in as many as 20% of cases the anterior arch de­ veloped from paired symmetrical ossification centers. The five common ossification centers of the axis arose in the paired neural arches, in the basal center, in the dentate center (from which most of the dentate process develops), and in the very apex of the dentate process. The appearance of each synchondrosis was noted at sequential ages (Fig. 7.2). The tubercles for the transverse ligament generally did not appear until the ossification of the synchondroses of the atlas was far advanced. Anomalies of the atlas included anterior and posterior spina bifida, absence of sectors of the posterior arch, and anomalous ossification centers and synchondroses. Anomalies of the axis were much less common. It was concluded that there is substantial variation in the time course and pattern of development of the atlas, and anomalies are common. Some fractures of the atlas may escape

recognition without manifest sequelae. Variation in the time course of the development of the axis is notable as well, but anomalies seem much less common.15

■■ Hangman’s Fracture Hangman’s fracture, or traumatic cervical spondylolisthesis, is the result of hyperextension trauma in combination with axial loading, rebound flexion, rebound extension, or distraction. The fractures are assessed by the Levine and Edwards classification, which is an adaptation of Effendi et al’s16 classification (Fig. 7.3): • Type 1: nondisplaced fracture with no angulation between C2 and C3 and a fracture dislocation of less than 3 mm • Type 2: fracture with significant angulation (> 11 degrees) and displacement (> 3.5 mm) • Type 2A: fracture with minimum displacement and significant angulation (> 11 degrees) • Type 3: fracture with severe angulation and displacement associated with unilateral or bilateral C2–3 facet dislocation Hangman’s fractures can be managed either conservatively, with immobilization, or surgi-

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Chapter 7

a

b

Fig. 7.3a,b  Hangman’s fractures can be classified by the Levine and Edwards classification25 (a), which is an adaptation of the Effendi classification16 (b). Type 1: nondisplaced fractures with no angulation between C2 and C3 and a fracture dislocation of less than 3 mm. Type 2: fracture with significant angu-

lation (> 11 degrees) and displacement (> 3.5 mm). Type 2A: fracture with minimum displacement and significant angulation (> 11 degrees). Type 3: fractures with severe angulation and displacement associated with unilateral or bilateral C2–3 facet dislocation.

cally. Most hangman’s fractures can be treated with cervical immobilization. External immobilization with a collar is regularly applied for the treatment of patients with type I fractures. Some authors also recommend initial external immobilization, usually with a halo vest, for types 2 and 2A. Type 3 and long-term nonfusion patients are usually treated with surgery. The most common surgical approach is a C1-C3 posterior fixation, but an anterior C2-C3 approach is also popular.16 With the introduction of navigation systems for the spine, the navigated screw placement in the C2 pedicle has made the C1-C2 pedicle fixation a safe procedure to surgically treat a hangman’s fracture.17 The fixation with pars screws (through the isthmus, crossing the fracture line) has been reported previously; it

is more appropriate to perform it with the current navigation systems.

Surgical Versus Conservative Treatment of Hangman’s Fracture There are few studies on the conservative versus surgical treatment of patients with a hangman’s fracture. Li et al18 performed a systematic review of the literature from 1966 to 2004 and found 32 reports on the management of hangman’s fractures. Regarding a primary therapy for hangman’s fractures, 20 papers (62.5%) advocated conservative treatment, and 11 of the remaining 12 papers suggested that conser­ vative treatment was suitable for some stable fractures. Most hangman’s fractures can be managed successfully with traction and external



Odontoid Fractures, Hangman’s Fractures, and C2 Body Fractures

immobilization, and surgical stabilization is recommended in unstable cases when there is the possibility of later instability, such as type IIa and III fractures with significant dislocation. Another systematic review of the literature from 1980 to 2010 covered only conservative treatment. It, too, found that traction is a good tool for realignment.19 In that review, four retrospective studies were identified that assessed the outcome of hangman’s fractures. These studies include a mix of patients with and without neurologic injury managed primarily with early traction and a rigid external orthosis. Neck pain and bothersome stiffness are not reported at long-term follow-up, although no objective pain scores were collected.

Biomechanical Study Unicortical or bicortical posterior screws can be placed. The use of bicortical screws entails a higher risk of damaging the spinal nerve or the vertebral artery, because the screw trajectory has to be prepared with a drill instead of a probe. Therefore, there would clearly be interest in determining whether there is a difference in the pullout strength of the screws. A biomechanical study using 11 human cadaveric cervical spines was conducted to determine whether the cervical stability achieved with lateral mass fixation using unicortical 14-mmlong screws is comparable with that obtained with lateral mass fixation using bicortical screws. Cervical spinal sections between C3 and C5 were tested in flexion-extension, torsion, and lateral bending modes, both with and without laminectomy, with uni- and bicortical 14-mm screws. Analysis demonstrated that bicortical constructs were, on average, stiffer than unicortical constructs in most bending modes after a wide laminectomy was performed. No significant differences were found, however, between bicortical constructs and unicortical constructs without laminectomy. 20 These results were not confirmed by another publication, where the same results in both uni- and bicortical lateral mass screw pullout strength was reported, even in combination with a laminectomy.21

■■ C2 Body Fractures The C2 body is the region that lies below the odontoid process (dens) and between the pars interarticularis of each side. Fractures of the C2 body are uncommon. Benzel’s group22 proposed a classification scheme that identified three types of C2 body fractures: (1) vertical, coronally oriented (type 1); (2) vertical, sagittally oriented (type 2); and (3) transverse, axially oriented (type 3). The vertical, coronally oriented type 1 C2 body fracture has been ­described by others as either an atypical traumatic spondylolisthesis of the axis or an unusual type of hangman’s fracture. The type 3 C2 body fracture is identical to the Anderson and D’Alonzo type III odontoid fracture. Fujimura and colleagues23 proposed the following classification scheme: Type I is an avulsion fracture due to hyperextension (teardrop fracture). Type II is a transverse fracture running horizontally through the C2 vertebral body caudal to the superior end of the atlantoaxial joint. The fracture line is caudal to that in the type III dens fracture. Type III is a burst fracture, or comminuted fracture of the C2 body with multiple fragments dislocated anteroposteriorly, often with retropulsion into the spinal canal. Traumatic spondylolisthesis is present in all cases. Type IV is a sagittal or parasagittal fracture extending from a point lateral to the dens vertically or diagonally to the inferior surface of C2.

Classification A treatment algorithm is desirable, especially for rare diseases. To that end, classifications of the observed injury can be helpful. It is therefore relevant to study whether the classifi­ cations proposed by Benzel and by Fujimura correlate with the outcome in surgical and nonsurgical treatment. German et al22 evaluated 18 patients who were classified, based on the Benzel classification, as having a vertical C2 body fracture. Sixteen coronally oriented type 1 vertical C2 body fractures and five sagittally oriented type 2 vertical C2 body fractures were identified. All patients were managed nonop-

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Chapter 7 eratively (with external orthoses) and showed evidence of fusion (union of fracture fragments) at the time of the last follow-up. The authors conclude that vertical C2 body fractures are amenable to nonoperative treatment from both a neurologic and an osteological viewpoint. They also report that vertical C2 body fractures are not rare injuries, as they accounted for 10% of the upper cervical spine fractures identified over the study period. No reports were identified on the treatment of Benzel type III horizontal C2 body fractures. Therefore, the Benzel classification is not helpful in determining what treatment should be applied. As a rule of thumb, we can only suggest that the vertical body fractures can be treated conservatively. Fujimara23 also proclaims nonoperative treatment of axis body fractures as the primary therapy. Fujimara claims to apply a cervical cast if no dislocation of the atlanto-axial joint or C2/3 is recognized. If however a dis­ location of the atlanto-axial joint or C2/3 is present, skull traction or traction with the ­halo-ring should be performed. Subsequently, upon achieving reduced position, a cervical cast or halo-vest should be put on and kept in a place for 8–16 weeks. Fujimara suggests a surgical intervention if it would be difficult to obtain or maintain the reduced position due to some associated injuries. Again, no correlation was made between the type of injury and the selected method of treatment. Both the Fujimara and the Benzel classifications are not helpful in deciding whether to perform a surgical intervention. The same logical rule of thumb that applies to all cervical trauma cases is valid: if the dislocation is severe, surgical intervention is advisable. Zhang et al24 provide indications for when a surgical strategy should be applied. They report on a retrospective analysis of 28 cases presenting with axis body fractures. They suggest the following indications for surgical treatment: (1) fractures associated with instability of adjacent joints; (2) irreducible displaced superior articular facet fracture; and (3) fractures resulting in spinal cord compression. The surgical procedures they applied were posterior C1-C2

pedicle screw application. Complications of malposition of screws and neurologic deficit did not occur in these 28 cases. Satisfactory reduction and bony union were demonstrated on postoperative radiographics. The authors conclude that conservative treatment is still advocated as the primary management for most axis body fractures, but that surgical intervention is necessary for patients with obvious adjacent joint instability or irreducible displaced superior articular facet fracture. No classification, neither Benzel’s nor Fujimara’s, is used to illustrate their conclusion.

■■ Chapter Summary In this chapter, the anterior and posterior surgical treatment of C2 odontoid fractures is described, and attention was paid to the balance between surgical and conservative treatment of C2 odontoid fractures. Furthermore, C2 anatomy in children is described and the variance in anatomy and development speed is stressed. The Hangman’s fracture treatment of the different types of fracture is discussed. Finally, C2 body fractures are discussed and it was concluded that in general conservative treatment is adequate, and that classification of this type of fracture is not helpful in making decisions on treatment.

Pearls ◆◆ In anterior screw fixation, a 10% nonunion rate is

reported in the literature; nonunion is significantly higher when patients are over 70 years of age. ◆◆ For type II/III odontoid fractures, surgically treated patients appear to show higher osseous union rates compared with conservatively treated patients, but this does not lead to higher stability rates in the surgically treated patients (retrospective data, subjected to attrition bias). ◆◆ Most hangman’s fractures can be managed successfully with traction and external immobilization, and surgical stabilization is recommended in unstable cases when there is the possibility of later instability, such as type IIa and III fractures with significant dislocation.



Odontoid Fractures, Hangman’s Fractures, and C2 Body Fractures Pitfalls

◆◆ Bicortical lateral mass screws do not have more

◆◆ C2 fractures in children are difficult to distinguish

◆◆ Vertical C2 body fractures are not rare injuries;

from synchondroses; the C2 fractures in children are likely to occur at the line of the former synchondrosis.

pullout strength than unicortical screws.

they account for 10% of upper cervical spine fractures. They generally heal well with conservative treatment with a stiff collar.

References

Five Must-Read References  1. Huybregts JG, Jacobs WC, Vleggeert-Lankamp CL. The optimal treatment of type II and III odontoid fractures in the elderly: a systematic review. Eur Spine J 2013;22:1–13 PubMed 2. Anderson LD, D’Alonzo RT. Fractures of the odontoid process of the axis. J Bone Joint Surg Am 1974;56: 1663–1674 PubMed 3. Hsu WK, Anderson PA. Odontoid fractures: update on management. J Am Acad Orthop Surg 2010;18: 383–394 PubMed 4. Huybregts JG, Jacobs WC, Peul WC, Vleggeert-­Lankamp CL. Rationale and design of the INNOVATE Trial: an international cooperative study on surgical versus conservative treatment for odontoid fractures in the elderly. BMC Musculoskelet Disord 2014;15:7 PubMed  5. Fehlings MG, Arun R, Vaccaro AR, Arnold PM, Chapman JR, Kopjar B. Predictors of treatment outcomes in geriatric patients with odontoid fractures: AOSpine North America multi-centre prospective GOF study. Spine 2013;38:881–886 PubMed 6. Robinson Y, Robinson AL, Olerud C. Systematic review on surgical and nonsurgical treatment of type II odontoid fractures in the elderly. Biomed Res Int 2014;2014:231948 PubMed  7. Smith JS, Kepler CK, Kopjar B, et al. Effect of type II odontoid fracture nonunion on outcome among elderly patients treated without surgery: based on the AOSpine North America geriatric odontoid fracture study. Spine 2013;38:2240–2246 PubMed 8. Grauer JN, Shafi B, Hilibrand AS, et al. Proposal of a modified, treatment-oriented classification of odontoid fractures. Spine J 2005;5:123–129 PubMed 9. Tian NF, Hu XQ, Wu LJ, et al. Pooled analysis of nonunion, re-operation, infection, and approach related complications after anterior odontoid screw fixation. PLoS ONE 2014;9:e103065 PubMed 10. Apfelbaum RI, Lonser RR, Veres R, Casey A. Direct anterior screw fixation for recent and remote odontoid fractures. J Neurosurg 2000;93(2, Suppl):227– 236 PubMed 11. Kaminski A, Gstrein A, Muhr G, Müller EJ. [Trans­ articular C1-C2 screw fixation: results of unstable odontoid fractures and pseudarthrosis in the elderly]. Unfallchirurg 2008;111:167–172 PubMed

12. Molinari RW, Khera OA, Gruhn WL, McAssey RW. Rigid cervical collar treatment for geriatric type II odontoid fractures. Eur Spine J 2012;21:855–862 PubMed 13. Feng G, Wendlandt R, Spuck S, Schulz AP. One-screw fixation provides similar stability to that of twoscrew fixation for type II dens fractures. Clin Orthop Relat Res 2012;470:2021–2028 PubMed 14. Sim HB, Lee JW, Park JT, Mindea SA, Lim J, Park J. Biomechanical evaluations of various C1-C2 posterior fixation techniques. Spine 2011;36:E401–E407 PubMed 15. Piatt JH Jr, Grissom LE. Developmental anatomy of the atlas and axis in childhood by computed tomography. J Neurosurg Pediatr 2011;8:235–243 PubMed 16. Effendi B, Roy D, Cornish B, Dussault RG, Laurin CA. Fractures of the ring of the axis. A classification based on the analysis of 131 cases. J Bone Joint Surg Br 1981;63-B:319–327 PubMed 17. Singh PK, Garg K, Sawarkar D, et al. Computed tomography-guided C2 pedicle screw placement for treatment of unstable hangman fractures. Spine 2014;39:E1058–E1065 PubMed 18. Li XF, Jiang WM, Yang HL, et al. Surgical treatment of chronic C1-C2 dislocation with absence of odontoid process using C1 hooks with C2 pedicle screws: a case report and review of literature. Spine 2011;36: E1245–E1249 PubMed 19. Lewkonia P, Dipaola C, Schouten R, Noonan V, Dvorak M, Fisher C. An evidence-based medicine process to determine outcomes after cervical spine trauma: what surgeons should be telling their patients. Spine 2012;37:E1140–E1147 PubMed 20. Muffoletto AJ, Yang J, Vadhva M, Hadjipavlou AG. Cervical stability with lateral mass plating: unicortical versus bicortical screw purchase. Spine 2003;28: 778–781 PubMed 21. Papagelopoulos PJ, Currier BL, Neale PG, et al. Bio­ mechanical evaluation of posterior screw fixation in cadaveric cervical spines. Clin Orthop Relat Res 2003;411:13–24 PubMed 22. German JW, Hart BL, Benzel EC. Nonoperative management of vertical C2 body fractures. Neurosurgery 2005;56:516–521, discussion 516–521 PubMed

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Chapter 7 23. Fujimura Y, Nishi Y, Kobayashi K. Classification and treatment of axis body fractures. J Orthop Trauma 1996;10:536–540 PubMed 24. Zhang YS, Zhang JX, Yang QG, Shen CL, Li W, Yin ZS. Surgical management of the fractures of axis body:

indications and surgical strategy. Eur Spine J 2014; 23:1633–1640 PubMed 25. Levine AM, Edwards CC. The management of traumatic spondylolisthesis of the axis. J Bone Joint Surg Am 1985;67:217–226 PubMed

8 Compression (AO Type-A Injuries) Nuno Neves

■■ Introduction The cervical spine is injured in 2 to 3% of patients who sustain blunt trauma, and the vast majority of these fractures and dislocations occurs in the subaxial spine.1,2 The subaxial cervical spine is anatomically and biomechanically similar to the thoracolumbar spine, in both its osseous and ligamentous elements, but its smaller dimensions and higher range of motion in all planes makes it more prone to injuries. Although compression injuries are the most common type in the thoracolumbar spine, in the cervical spine they are relatively rare and account for less than 15% of all injuries.3 Characteristically, A-type compression fractures result from axial compression with or without flexion, have reduced vertebral body height, and have an intact posterior ligamentous complex. This chapter reviews the classification, clinical and diagnostic features of A-type compression fractures of the subaxial cervical spine, and discusses their management.

■■ Methods A literature search was performed on the National Library of Medicine (PubMed) database, using the following as the major search terms: cervical spine, fractures, injuries, burst fractures,

and compression fractures. Original papers and reviews were selected based on their relevance. Other articles were found through the references of the selected papers.

■■ Classification of Injuries of

the Subaxial Cervical Spine

An effective classification system establishes easy-to-remember, standardized terminology that both facilitates communication between health care providers and guides treatment.4 Furthermore, intra- and interobserver reliability should be high. The AO (Arbeitsgemeinschaft für Osteosynthesefragen) classification for spine injuries, as described by Magerl et al,5 was originally developed for the thoracolumbar spine, and is a comprehensive system primarily based on the morphology and mechanism of injuries. This system has three main types: type A, vertebral body compression; type B, disruption of the anterior and posterior elements with distraction; and type C, disruption of the anterior and posterior elements with rotation. Each type is further divided into three groups and three subgroups, for a complete description of every injury. Although specifically developed for the thoracic and lumbar spine, the idea of expanding its use for the cervical spine has been met with



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Chapter 8 Table 8.1  AO Classification of Subaxial Cervical Spine Compression Injuries A—Compression A1—Impaction fractures

A2—Split fractures

A3—Burst fractures

A1.1—end-plate impaction A1.2—wedge impaction A1.3—vertebral collapse

A2.1—sagittal or coronal A2.2—sagittal and coronal A2.3—pincer fracture

A3.1—incomplete burst A3.2—burst-split A3.3—complete burst

Source: From Blauth MKA, Mair G, Schmid R, Reinhold M, Rieger M. Classification of injuries of the subaxial cervical spine. In: Aebi M, Arlet V, Webb JK, eds. AOSpine Manual: AOSpine International. New York: Thieme; 2007:21–38. Reproduced with permission.

interest, because it represents a unified, comprehensive classification for the whole subaxial mobile spine. In a retrospective study of 448 patients, Blauth et al3 applied the AO thoracolumbar classification to the cervical spine, which the authors felt differed very little from its thoracolumbar counterpart (Table 8.1). Computed tomography (CT) is mandatory for the full classification of a cervical spine injury, and flexion-extension X-rays or magnetic resonance imaging (MRI) may also be required to identify possible injuries to the posterior ligamentous complex. Intraoperative findings may modify even further the initial classification. Although it is comprehensive, this system may become too complex beyond the type (A, B, or C) and group classification to apply in everyday practice, making it more useful for academic description of injuries. The AO is in the process of refining the AO subaxial cervical spine classification, combining elements of the Thoracolumbar Injury Classification and Severity Score (TLICS) system along with the principles of the original AO Magerl system. A widely used classification system is the Allen-Ferguson system, which is based on the mechanism involved in each lesion inferred from the radiographic images.6 There are six categories: (1) flexion-compression, (2) vertical compression, (3) flexion-distraction, (4) extension-compression, (5) extension-distraction, and (6) lateral flexion. These systems rely on morphological characteristics and inferred mechanisms, which poses several questions regarding their validity. The same mechanism may produce differ-

ent patterns of injury, and identifying a specific mechanism from a certain injury may be troublesome. Additionally, the classification fails to consider ligamentous stability or neurologic involvement, so its clinical applicability is limited. More recently, based on modern imaging, two new classification systems have been developed, enabling a continuous quantification of stability and aiding in decision making. The Cervical Spine Injury Severity Score (CSISS) independently analyzes four columns (anterior, posterior, right lateral column, and left lateral column) and scores each using a 0 to 5 analogue scale.7 Scores increase proportionally to either displacement of fracture fragments or separation as a result of soft tissue injury. Each column is scored independently and summed, yielding a score range of 0 to 20. Excellent intra- and interobserver reliability was obtained using this scale. Patients with a score ≥ 7 are treated surgically. AO A-type compression injuries score low on the CSISS (0–3), as they are limited to the anterior column. The Subaxial Cervical Spine Injury Classification (SLIC) system evaluates three parameters: fracture morphology, the discoligamentous complex (DLC), and neurologic function.4 Each is assigned a specific number of points, creating a score that aids treatment decision making. An injury that scores below 4 can be treated nonoperatively, whereas surgery is recommended with a score above 4. Injuries scoring equal to 4 can be managed either way. AO A-type compression injuries score low in the SLIC system (1–2) unless a neurologic deficit is present.



■■ Epidemiology According to Blauth et al,3 A-type fractures represent 14.7% of all subaxial spine injuries. In this study, A3 were the most common (9.8%) and A1 and A2 accounted for only 2.9% and 2.0%, respectively. This is in stark contrast with the thoracolumbar spine, where compression and burst fractures are largely predominant. In a study of 203 vertebral fractures in 127 patients, burst fractures accounted for 38% of the fractures, but only 10% were located in the cervical spine.8 Importantly, all patients with a single spine fracture should undergo imaging of the entire axis, as at least 10% of patients may have a noncontiguous spinal fracture.8,9 Axial compressive cervical spine fractures are typically observed in the third and fourth decades of life, and men are predominantly affected, with falls and sports activities (e.g., diving head first in shallow water) being the main causes of injury.9,10 Spinal cord injuries (SCIs), either complete or incomplete, are frequently associated with burst fractures. According to Blauth et al,3 neurologic injuries (ranging from radicular symptoms to severe complete SCI) were observed in 54.5% of all cervical spine burst fractures. Only 15.3% and 22.2% of neurologic injuries were associated with A1 and A2 types, respectively, representing the groups with the least complications. Young men in their early 30s are the group at higher risk of sustaining SCI, but the demographics are variable throughout the world, and a recent shift toward more women and older age has been described.11

■■ Diagnostic Features A-type fractures characteristically result from axial compression. They are usually associated with variable degrees of flexion, and they have reduced vertebral body height and an intact posterior ligamentous complex. Impaction fractures (group A1) are rare injuries that result from axial loading forces in flexion. The disc is pressurized, leading to wedg-

Compression (AO Type-A Injuries) ing of the vertebral body, which usually occurs along the superior end plate. Because the posterior body cortex is intact, and commonly there is no injury to the posterior ligamentous complex (PLC), the risk of neurologic injury is low. However, damage to the PLC can occur with A1-type fractures creating an unstable lesion, and the association of a vertebral compression fracture with interspinous space widening, vertebral subluxation, and loss of cervical lordosis, indicates a probable ligamentous disruption, the so-called hidden flexion injury.12 A high level of suspicion is necessary to identify these injuries, as they can be spontaneously reduced in supine lateral X-rays, and flexion-extension images under fluoroscopic control or advanced imaging modalities may be indicated. Split fractures (group A2) are rare lesions. Because pure coronal or sagittal plane fracture lines are uncommon, this group presents a minor change from its thoracolumbar classification counterpart, including combined sagittal and coronal plane fractures. In the pincer-type fracture (A2.3), there is marked displacement of the anterior fragment and small comminution zones, leading to reduced resistance to compression and increased susceptibility to nonunion. Burst fractures (group A3) result from severe axial loading, affecting both the anterior and middle columns of the cervical vertebrae and usually occur at C6 and C7 rather than the middle or upper cervical spine.4,6 With axial loading, pressure increases rapidly inside the disc, pushing the superior end plate inside the vertebral body, which fails with retropulsion of fragments to the spinal canal. The posterior vertebral body cortex is injured, leading to decreased anterior and posterior vertebral height and a variable degree of segmental kyphosis. Incomplete burst fractures are less common than in the thoracolumbar spine, as usually the whole posterior wall of the vertebral body bulges into the spinal canal. Because the head is often slightly flexed, posterior ligamentous complex disruption can occur and must be ruled out by appropriate methods. In anteroposterior (AP) views (Fig. 8.1a), X-rays reveal a vertical fracture line, pedicle

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Chapter 8

a

b

Fig. 8.1a–e  A 48-year-old man suffered an injury in a motor vehicle accident. He was admitted to the hospital with neck pain and an incomplete spinal cord injury (American Spinal Injury Association [ASIA] grade B). (a,b) X-rays and (c) computed tomography (CT) scan revealed a C5 complete burst fracture with vertebral body comminution and retropulsion of the posterior cortex. The patient was put in skull traction for immediate reduction and indirect spinal cord decompression and underwent a C5 corpectomy, C4-C6 fusion with iliac crest bone graft, and plate fixation.

c

widening, and variable degrees of comminution and displacement of fragments of the vertebral body. On lateral views (Fig. 8.1b), there is soft tissue swelling, shortening of both anterior and posterior vertebral body heights, variable kyphosis, and convexity of the posterior vertebral body wall as compared with the normal vertebrae. As the pedicles are pushed laterally, verti-

cal fractures in the laminae or spinous processes can also be seen. Failure of the anterior column, severe kyphosis, interspinous widening, forward subluxation of the adjacent vertebral body, facet subluxation, fracture, or dislocation, are highly suggestive of disruption of the DLC. A CT scan can precisely define bone comminution, posterior wall retropulsion, and facet



Compression (AO Type-A Injuries)

d

87

e

Fig. 8.1a–e (continued)  (d,e) One year later the fusion has healed uneventfully and the neurologic status improved to ASIA grade D.

subluxation or fractures, which are difficult to visualize in conventional radiography (Fig. 8.1c). However, because retropulsed fragments often have recoiled from the most displaced position, the CT scan can significantly under­ estimate the amount of canal narrowing that occurs during the impact, and so there is no direct correlation between postinjury occlusion and neural damage.13 Moreover, CT scan can easily image the occipitocervical and cervicothoracic spine, which are difficult to assess with plain radiographs. Magnetic resonance imaging is used to evaluate ongoing neurologic compression and soft tissue injuries, and is indicated in all patients with a neurologic deficit unless obtaining the study would lead to a substantial delay in treatment. A hyperintense signal through ligamentous regions on T2 or short tau inversion recovery (STIR) images is indicative of a ligamentous injury. Still, there is no definitive clinical correlation between increased ligamentous signal and mechanical instability.4

■■ Initial Management Patients with A-type injuries are kept immobilized with a hard cervical collar with the spine in a neutral position. A cadaveric study demonstrated that flexion or extension can decrease canal diameter in a patient with a burst fracture of the cervical spine.14 Once the neck has been properly immobilized, periodic neurologic exams should be performed. Although there is little high-quality evidence on closed reduction of cervical burst fractures by skull traction, it can be performed as a means of achieving indirect neural decompression in an emergent setting.15 Even if surgical treatment has already been decided, this temporizing measure may help restore the anatomic alignment and make surgery easier. Gardner-­ Wells tongs are initially applied with 5 kg to counter the weight of the head; sequentially, and under close supervision, 2 kg for each segment is added, and radiographs or fluoroscopy are used to control reduction. For burst fractures,



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Chapter 8 additional weight is rarely needed to achieve acceptable alignment and reduction. Alternatively, a halo may be used both for reduction and definitive nonoperative treatment.

■■ Definitive Management There are three main factors to consider when deciding whether or not to surgically stabilize a subaxial cervical spine injury: spinal stability, neurologic status, and individual patient factors.16 A significant portion of A-type injuries has neither neurologic compromise nor mechanical instability, so these injuries can be treated nonoperatively. The AO subaxial spine classification system does not consider the neurologic status of the patient, but rather relies on morphological characteristics and the mechanism of injuries to establish the severity of the fracture. However, defining instability has been a challenge and a matter of intense debate and confusion. White and Panjabi’s group17 defined stability as “the ability of the spine under physiologic loads to limit patterns of displacement so as not to damage or irritate the spinal cord or nerve roots and, in addition, to prevent incapacitating deformity or pain due to structural changes,” and developed a checklist to assist in the determination of spinal stability. They identified radiographic parameters for subaxial cervical spine instability including more than 3.5 mm horizontal displacement of one vertebra in relation to an adjacent vertebra, or more than 11 degrees of rotation difference from that of either adjacent vertebra. Although helpful and reliable in extreme cases, this definition may be inadequate in subtle cases, as instability is a continuum of situations rather than a dichotomous condition. The SLIC system carefully analyzes each of three components of the injury: fracture morphology, integrity of the DLC, and neurologic function.4 For morphology, A1- and A2-type injuries are assigned one point and A3 fractures are assigned an additional point. The SLIC system then evaluates the integrity of the

DLC (intervertebral disc, anterior and posterior longitudinal ligaments, interspinous ligaments, facet capsules, and ligamentum flavum). An intact DLC is defined as normal spinal alignment, normal disc space, and ligamentous appearance, and is awarded zero points. Disruption of the DLC may be inferred by the presence of abnormal facet alignment (articular apposition 2 mm through the facet joint), widening of the anterior disc space, translation or rotation of the vertebral bodies, kyphotic alignment of the cervical spine, or high signal intensity seen horizontally through a disc involving the nucleus and anulus on T2 or STIR sagittal MRI, and is assigned two points. An indeterminate injury exists when radiographic disruption of the DLC is not obvious, but a hyperintense signal is found through ­either the disc or the posterior ligaments on MRI; this is assigned one point. Finally, neurologic status is assessed, and zero to four points are assigned. Injuries scored above four should be treated surgically, and nonoperative treatment can be recommended for those scoring below four. Injuries scoring equal to 4 can be managed either operatively or conservatively. In anterior column injuries (impaction, split, or burst), the integrity of the DLC must be carefully evaluated before deciding between the treatment options. Only one study has specifically compared the results of nonoperative and anterior operative treatment of cervical spine compression injuries.18 Sixty-nine consecutive patients with both cervical burst and flexion teardrop fractures were reviewed retrospectively. Thirty-­ four were treated with skull traction or halo vest, and 35 with anterior decompression, bone grafting, and plate fixation. Surgically treated patients had significantly better neurologic recovery, and had less narrowing of the spinal canal and kyphotic deformity at the end of the follow-up period. These results should be carefully analyzed, because no distinction was made between the two fracture types or between neurologically intact and injured patients. Moreover, the study was performed before the SLIC system was in use, and so the integrity of the DLC was not reported.



Nonoperative Treatment Because A1 and A2 type fractures are uncommon, there is no study comparing surgical versus conservative treatment in these specific types of injuries. Nevertheless, they are inherently stable lesions that have a low SLIC score, and a strong recommendation can be made for nonoperative management in neurologically intact patients. The association of interspinous space widening, vertebral subluxation, and loss of cervical lordosis indicates a possible ligamentous disruption, and these patients require close follow-up, as these injuries may displace later on. Pincer-type fractures (A2.3) without disruption of the DLC should undergo initial nonoperative management, and similarly many burst fractures without injury to the DLC can be treated nonsurgically. The use of braces or a halo vest immobilizes the spine during healing, maintaining spinal alignment, and controls pain by restricting movement. Stable impaction or split fractures can be treated with a cervical collar. Burst fractures may need a hard cervical thoracic orthosis (CTO) or a halo vest, especially in those cases where prior reduction was performed. Frequent radiographs must be obtained to closely monitor the reduction and alignment until union is achieved, which can take up to 12 weeks. Dynamic flexion-extension radiographs should be taken at the end of the immobilization period to detect any residual dynamic instability. Inability to maintain alignment and reduction may predispose to late pain or de novo neurologic deficits, and may warrant surgical stabilization. Physical therapy is usually prescribed at the end of treatment. Nonoperative treatment can result in significant complications.19 Cervical orthoses may be associated with discomfort, inadequate immobilization, muscle atrophy, psychological dependence, pain, skin breakdown, and worsened pulmonary function. Optimized fit and adequate, soft materials at skin contact sites can enhance comfort and compliance with treatment. Halo vest use can significantly impair daily life and result in multiple complications, such as pin loosening, penetration and infection, pres-

Compression (AO Type-A Injuries) sure sores, subdural abscess, nerve palsies, and fracture overdistraction. The use of a halo vest is relatively contraindicated in the presence of severe cachexia, in patients with severe deformity (ankylosing spondylitis or scoliosis), in morbid obese patients, in the elderly, and in noncompliant or tetraplegic patients.

Surgical Treatment Accepted indications for surgery in anterior column compression injuries are as follows: (1) neurologic deficit; (2) disruption of the DLC; and (3) inability to proceed with conservative treatment (e.g., fractured skull precluding halo application) or to maintain satisfactory reduction and alignment. As mentioned above, in the only study available that compared nonoperative management with anterior operative management of cervical spine compression injuries, the results favored surgical treatment.18 However, no definitive indications can be drawn from this study, ­because results were reported without clear distinction between neurologically intact and injured patients, and the DLC was not specifically assessed. No class I or II evidence addressing the surgical approach in compression and burst fractures is available, and only eight class III studies were identified.20–27 Reports include mixed fracture patterns and small numbers of patients, and most were performed before contemporary classification systems were in use. Brodke et al20 compared the results of anterior versus posterior surgery in 57 patients with unstable cervical spine lesions and associated spinal cord injuries, but only seven had isolated burst fractures (four in the anterior group and three in the posterior group). Twelve patients had a burst fracture associated with a  clear distraction injury. Neurologic improvement and a high fusion rate were observed in each group, with no significant differences; however, in the anterior group, 70% improved at least one Frankel grade, compared with 57% in the posterior group. Toh et al21 reviewed the surgical treatment of 31 patients with burst or flexion distraction

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Chapter 8 injury in the middle and lower cervical spine who were treated with anterior instrumen­ tation, posterior instrumentation, or both. Because all burst fractures were approached anteriorly, a comparison of treatments for this specific type of injury is not possible. Nevertheless, anterior decompression and fusion restored the spinal canal diameter significantly better, and improved neurologic function in nine of 24 patients, whereas no improvement was observed in those treated posteriorly. Complications and overall alignment were evaluated in a study of 29 patients with an unstable cervical vertebral fracture or a fracture-­ dislocation treated with posterior spine fusion and lateral mass instrumentation.22 There were seven vertical compression burst fractures. A mean loss of 2 degrees in sagittal alignment at the final follow-up examination was observed, with no differences between the various types of injury patterns. Six complications were reported: four wound infections, one hardware failure, and one C5 nerve root injury. Lambiris et al23 performed a retrospective study of patients with different subaxial cervical spinal injuries to summarize the compli­ cations of instrumented anterior or posterior stabilization of cervical spine injuries. No difference in the complication rate between anterior (74 patients) and posterior (23 patients) fixation was observed. Nevertheless, nearly all eight compression wedge injuries and 13 burst fractures were treated anteriorly, as proposed by their treatment algorithm. The use of pedicle screw instrumentation was also evaluated in a retrospective series of 144 unstable cervical injury patients.24 An overall low rate of instrumentation-related and other complications was observed with this surgical technique. Kasimatis et al25 reported on 74 patients with unstable lower cervical spine injuries who underwent anterior surgery over a 15-year period. There were seven compression wedge and 13 burst fractures, and the results were not stratified according to injury type. Overall, 90% of incomplete lesions improved, there was no neurologic deterioration and no instrumentation failure, and all fusions healed.

Belirgen et al26 retrospectively analyzed the results of anterior versus posterior surgery in a group of 33 patients with reducible cervical subaxial fractures. There were only four compression-type injuries, and the results were not reported specifically for this subgroup. Posterior surgery was associated with longer operative times and more blood loss, and entailed a larger number of fused segments. The authors concluded that anterior instrumentation with interbody grafting can be the initial choice of treatment for stabilization of these patients, and that posterior surgery is indicated if radiographs show failure after anterior instrumentation. The Spine Trauma Study Group developed an evidence-based algorithm for surgical approaches to the management of subaxial cervical spine injuries based on a systematic review of the literature, expert opinion, and anticipated patient preferences.27 The algorithm is derived from the SLIC system and addresses both the indication for surgery as well as the surgical approach. Compression and burst fractures without disruption of the DLC are awarded one or two points and commonly zero for an intact DLC. Hence, the neurologic status and the presence of residual compression of the spinal cord are the strongest determinants of treatment. With complete or incomplete neurologic injury, the SLIC system will add two to four points to the morphology score, leading to an overall score of four to six. Surgery is preferred with scores of five or above. Scores of four should be decided case by case, depending on the surgeon’s preferences and experience, and the patient’s factors and expectations. The authors recommended anterior decompression and stabilization for surgically treated burst fractures. From the aforementioned studies we can conclude that anterior decompression and stabilization is favored when surgery is indicated for burst fractures. Patient positioning is safe and straightforward for an anterior approach, and surgical dissection is performed with minimal soft tissue damage. Because spinal cord compression is ventral, optimal decompression of neural elements can be done under direct



Compression (AO Type-A Injuries)

visualization. Corticocancellous autogenous strut graft, allograft, or a cage can be inserted and supplemented by a plate (Fig. 8.1d,e). Because of its ready availability, low cost, and predictable fusion rate, we usually prefer iliac bone autograft. After surgery, a cervical collar can be worn, especially in more unstable cases, but there are no strict indications on either its use or the duration of immobilization. Impaction wedge and split fractures with surgical indication can be stabilized by anterior or posterior fixation. Posterior monosegmental fusion with lateral mass screws is an easy, reliable, and biomechanically valid surgery for the treatment of these injuries. However, we prefer anterior stabilization. A wedge-shaped graft is inserted and a variable-angle screw plate is applied to take purchase in the intact lower portion of the vertebral body. With contemporary implants and a correctly fashioned graft, the risk of subsidence is probably minimal.

■■ Treatment

Recommendations

Neurologically Intact Patients • A-type fractures without disruption of the DLC can be treated nonoperatively with a collar, a hard cervical thoracic orthosis, or a halo vest, depending on the severity of the injury. • Impaction and split fractures with disruption of the DLC can be treated conservatively, but careful, frequent monitoring of reduction and alignment is needed, as these injuries may displace. • Burst fractures with disruption of the DLC can be treated either conservatively or surgically. Surgical treatment may be preferred because of the risk of displacement, neurologic compromise, late pain, and the minimal risks of anterior stabilization. However, because the long-term morbidity of losing two mobile levels may be significant, strong consideration must be given to conservative treatment, especially in the young patient.

• Inability to achieve or maintain correct reduction and alignment is an indication for surgery.

Neurologically Injured Patients • Neurologic injury warrants immediate reduction and indirect decompression using skull tongs or halo traction, particularly if surgery is delayed. • Surgery is indicated, especially in incomplete spinal cord lesions and continuous cord compression, by direct anterior decompression, interbody grafting, and plating.

■■ Chapter Summary A-type compression fractures (impaction, split and burst fractures) characteristically result from axial compression, and commonly have a reduced vertebral body height and an intact posterior ligamentous complex. Contrary to what happens in the thoracolumbar spine, where compression fractures are the most common type, in the cervical spine they are relatively rare and account for less than 15% of all injuries. Typically, these injuries occur in young men, and falls and sports activities are the main causes of injury. More than half of cervical burst fractures can be associated with either complete or incomplete spinal cord injury. A-type fractures, without neurologic damage can be treated nonoperatively with a collar, a hard cervical thoracic orthosis, or a halo vest, depending on the severity of the injury, as long as the DLC has been thoroughly evaluated. Disruption of the DLC is not an absolute operative indication, as compression and split fractures with disruption of the DLC can still be treated conservatively. Importantly, patients with a possible DLC disruption require frequent monitoring, as these injuries may displace. Burst fractures in neurologically intact patients with disruption of the DLC can be treated either conservatively or surgically. Because of the risk of displacement, neurologic compro-

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Chapter 8 mise, and late pain, and considering safety and efficacy of anterior stabilization, surgical treatment may be preferred. However, strong consideration must be given to conservative treatment, because the morbidity of losing two mobile levels may be significant in the long term, especially in a young patient. Neurologic injury warrants immediate closed or open reduction, and surgery is indicated for all patients with a persistent neurologic deficit. Our preferred approach is a direct anterior decompression, interbody grafting, and plating. In addition to neurologic injuries, the failure to achieve or maintain correct reduction and alignment is also an indication for surgery.

surgery, especially in those patients where co­ existing injuries delay definitive intervention. ◆◆ Most A-type fractures in neurologically intact patients can be treated nonoperatively, provided that DLC disruption has been appropriately ruled out. ◆◆ If feasible and adequate, conservative treatment of burst fractures with disruption of the DLC in neurologically intact patients can be used, considering the long-term morbidity of losing two mobile levels. ◆◆ Anterior decompression, interbody grafting, and plate stabilization are the preferred treatment in neurologically injured patients. Pitfalls ◆◆ A high level of suspicion is necessary to identify

Pearls ◆◆ A-type compression fractures represent less than

15% of all subaxial spine injuries.

◆◆ Axial compressive cervical spine fractures are

typically observed in men in the third and fourth decades of life, and falls and sports activities are the main causes of injury. ◆◆ Burst fractures usually affect the lower cervical spine (C6 or C7), and neurologic injuries are present in more than half of the patients. ◆◆ Skull traction can be performed for indirect neural decompression in an emergent setting, even if surgical treatment has already been decided, as this will enable anatomic alignment and an easier

ligamentous disruption in compression injuries, as they can be spontaneously reduced in supine lateral X-rays, and flexion-extension images under fluoroscopic control or advanced imaging modalities may be indicated. ◆◆ Patients with burst injuries should be kept immobilized with a hard cervical collar, with the spine in neutral position, because either extension or flexion has been associated with an increase in the occlusion of the spinal canal. ◆◆ If conservative treatment is undertaken, frequent radiographs should be obtained to closely monitor the reduction and alignment until union is achieved. Loss of reduction or alignment may warrant surgical stabilization.

References

Five Must-Read References 1. Goldberg W, Mueller C, Panacek E, Tigges S, Hoffman JR, Mower WR; NEXUS Group. Distribution and patterns of blunt traumatic cervical spine injury. Ann Emerg Med 2001;38:17–21 PubMed 2. Lowery DW, Wald MM, Browne BJ, Tigges S, Hoffman JR, Mower WR; NEXUS Group. Epidemiology of cervical spine injury victims. Ann Emerg Med 2001;38: 12–16 PubMed  3. Blauth MKA, Mair G, Schmid R, Reinhold M, Rieger M. Classification of injuries of the subaxial cervical spine. In: Aebi M, Arlet V, Webb JK, eds. AOSpine Manual: AOSpine International. New York: Thieme; 2007:21–38  4. Vaccaro AR, Hulbert RJ, Patel AA, et al; Spine Trauma Study Group. The subaxial cervical spine injury classification system: a novel approach to recognize the importance of morphology, neurology, and integrity of the disco-ligamentous complex. Spine 2007;32: 2365–2374 PubMed

5. Magerl F, Aebi M, Gertzbein SD, Harms J, Nazarian S. A comprehensive classification of thoracic and lumbar injuries. Eur Spine J 1994;3:184–201 PubMed 6. Allen BL Jr, Ferguson RL, Lehmann TR, O’Brien RP. A  mechanistic classification of closed, indirect fractures and dislocations of the lower cervical spine. Spine 1982;7:1–27 PubMed 7. Anderson PA, Moore TA, Davis KW, et al; Spinal Trauma Study Group. Cervical spine injury severity score. Assessment of reliability. J Bone Joint Surg Am 2007;89:1057–1065 PubMed 8. Bensch FV, Kiuru MJ, Koivikko MP, Koskinen SK. Spine fractures in falling accidents: analysis of ­multidetector CT findings. Eur Radiol 2004;14:618– 624 PubMed  9. Bensch FV, Koivikko MP, Kiuru MJ, Koskinen SK. The incidence and distribution of burst fractures. Emerg Radiol 2006;12:124–129 PubMed

10. Blackmore CC, Mann FA, Wilson AJ. Helical CT in the primary trauma evaluation of the cervical spine: an evidence-based approach. Skeletal Radiol 2000;29: 632–639 PubMed 11. Wyndaele M, Wyndaele JJ. Incidence, prevalence and epidemiology of spinal cord injury: what learns a worldwide literature survey? Spinal Cord 2006;44: 523–529 PubMed 12. Webb JK, Broughton RB, McSweeney T, Park WM. Hidden flexion injury of the cervical spine. J Bone Joint Surg Br 1976;58:322–327 PubMed 13. Carter JW, Mirza SK, Tencer AF, Ching RP. Canal geometry changes associated with axial compressive cervical spine fracture. Spine 2000;25:46–54 PubMed 14. Ching RP, Watson NA, Carter JW, Tencer AF. The effect of post-injury spinal position on canal occlusion in a cervical spine burst fracture model. Spine 1997;22: 1710–1715 PubMed 15. Grant GA, Mirza SK, Chapman JR, et al. Risk of early closed reduction in cervical spine subluxation injuries. J Neurosurg 1999;90(1, Suppl):13–18 PubMed 16. Kwon BK, Vaccaro AR, Grauer JN, Fisher CG, Dvorak MF. Subaxial cervical spine trauma. J Am Acad Orthop Surg 2006;14:78–89 PubMed 17. White AA III, Johnson RM, Panjabi MM, Southwick WO. Biomechanical analysis of clinical stability in the cervical spine. Clin Orthop Relat Res 1975;109: 85–96 PubMed 18. Koivikko MP, Myllynen P, Karjalainen M, Vornanen M, Santavirta S. Conservative and operative treatment in cervical burst fractures. Arch Orthop Trauma Surg 2000;120:448–451 PubMed 19. Lauweryns P. Role of conservative treatment of cervical spine injuries. Eur Spine J 2010;19(Suppl 1): S23–S26 PubMed

Compression (AO Type-A Injuries) 20. Brodke DS, Anderson PA, Newell DW, Grady MS, Chapman JR. Comparison of anterior and posterior approaches in cervical spinal cord injuries. J Spinal Disord Tech 2003;16:229–235 PubMed 21. Toh E, Nomura T, Watanabe M, Mochida J. Surgical treatment for injuries of the middle and lower cervical spine. Int Orthop 2006;30:54–58 PubMed 22. Pateder DB, Carbone JJ. Lateral mass screw fixation for cervical spine trauma: associated complications and efficacy in maintaining alignment. Spine J 2006; 6:40–43 PubMed 23. Lambiris E, Kasimatis GB, Tyllianakis M, Zouboulis P, Panagiotopoulos E. Treatment of unstable lower cervical spine injuries by anterior instrumented fusion alone. J Spinal Disord Tech 2008;21:500–507 PubMed 24. Yukawa Y, Kato F, Ito K, et al. Placement and complications of cervical pedicle screws in 144 cervical trauma patients using pedicle axis view techniques by fluoroscope. Eur Spine J 2009;18:1293–1299 PubMed 25. Kasimatis GB, Panagiotopoulos E, Gliatis J, Tyllianakis M, Zouboulis P, Lambiris E. Complications of anterior surgery in cervical spine trauma: an overview. Clin Neurol Neurosurg 2009;111:18–27 PubMed 26. Belirgen M, Dlouhy BJ, Grossbach AJ, Torner JC, Hitchon PW. Surgical options in the treatment of subaxial cervical fractures: a retrospective cohort study. Clin Neurol Neurosurg 2013;115:1420–1428 PubMed 27. Dvorak MF, Fisher CG, Fehlings MG, et al. The surgical approach to subaxial cervical spine injuries: an evidence-based algorithm based on the SLIC classification system. Spine 2007;32:2620–2629 PubMed

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9 Subaxial Cervical Spine Injuries: Distraction (AO Type-B Injuries) William A. Robinson, Kevin P. McCarthy, Alexander R. Vaccaro, and C. Chambliss Harrod

■■ Introduction Of the 150,000 cervical spine injuries that occur annually in North America, 7 to 8% are associated with spinal cord injuries, which are more frequent among Caucasians, the elderly, and males.1,2 Subaxial (C3–C7) injuries account for 75% of spinal cord injuries. The AO (Arbeitsgemeinschaft für Osteosynthesefragen) classifies subaxial cervical fractures into compression (type A), distraction (type B), and rotation (type C) injuries. Distraction injuries typically occur from excessive flexion (more common) or extension mechanisms and may represent 25 to 30% of subaxial injuries and are most common at C5–C6 (flexion) and C6–C7 (extension).3 Flexion-­distraction injuries (FDIs) often entail compression of the anterior column and distraction of the posterior elements, whereas extension-distraction injuries (EDIs) compress posteriorly and distract the anterior column. Patients with ankylosing spinal disorders (ASDs) [ankylosing spondylitis (AS) and diffuse idiopathic skeletal hyperostosis (DISH)] have unique diseases that are often associated with missed fractures, increased neurologic injuries, epidural hematomas, and poorer outcomes.4 Treatment depends on timely initial evaluation and diagnosis of spinal and nonspinal injuries, use of diagnostic studies, and integration of fracture morphology, spinal stability, neurologic status, and comorbidities. Classification of subaxial fractures has been controversial,

but the goal is to establish a clinically relevant, reliable, prognostic system that guides treatment. Neurologic status (as determined by the American Spinal Injury Association [ASIA] scale), radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) are vital diagnostic tools to accurately classify subaxial fractures.5–7 Closed reduction with craniocervical traction is often performed promptly, and operative intervention is necessary to maintain reduction and stabilize injured segments while protecting or decompressing the neural elements. This chapter reviews the management of cervical subaxial flexion and extension distraction injuries, focusing on evaluation, imaging, and evidence-based treatment recommendations regarding closed reduction, nonoperative versus operative treatment, the selection of the optimal approach, and special issues in the management of ASD patients.

■■ Evidence-Based Medicine:

Literature and Clinical Recommendations

Level of evidence ratings have been established using criteria set by the Journal of Bone and Joint Surgery, American Volume.8 Ideally, evidence-­ based protocols are developed using the overall body of evidence with respect to each clinical

question and the precepts outlined by the Grades of Recommendation Assessment, Development and Evaluation (GRADE) Working Group9 and recommendations made by the Agency for Healthcare Research and Quality (AHRQ).10 The strength of evidence grade for each outcome or clinical question, which is categorized as high, moderate, low, or insufficient, is described in further detail in Spine systematic reviews that have proven instrumental in reviewing controversial spine topics.11 In contemporary systematic review study groups, clinical recommendations or consensus statements are often made through a modified Delphi approach by applying the GRADE/ AHRQ criteria that impart a deliberate distinction between the strength of the evidence (i.e., high, moderate, low, or insufficient) and the strength of the recommendation. When appropriate, recommendations or statements “for” or “against” are given “strong” or “weak” designations based on the quality of the evidence, the balance of benefits/harms, and values and patient preferences.11 Typically, these systematic reviews limit study inclusion to level I, II, and III studies (prospective randomized controlled trials and cohort studies with exclusion of case series, case reports, cadaver studies, and studies with fewer than 10 cases). Unfortunately, the literature regarding cervical distraction injuries is essentially level IV or V (case series, case reports, cadaver studies, and studies with fewer than 10 cases); therefore, we will highlight important papers that are thought to influence decision making and to guide treatment.

Classifications and Morphology Distraction injuries occur in flexion or extension patterns. Hyperextension injuries typically occur in patients with stiff spines such as the elderly (spondylosis) or in patients with DISH or AS. Failure of the anterior and middle columns (EDI stage I) occurs with or without posterior element disruption and possible subluxation/ dislocation (stage II) with central cord syndromes often associated. FDIs affect primarily posterior elements, with a broad array of injuries ranging from facet subluxation (stage I), to

Distraction (AO Type-B Injuries) unilateral perch/dislocation (stage II), to stage III (≤ 50%) and stage IV (> 50%) bilateral dislocation with anterior cord syndromes often associated. There are multiple classification schemes for subaxial cervical spine injuries. The lack of a uniformly accepted classification system has greatly hindered both high-quality research and efforts to establish optimal evidence-based treatment algorithms. The evidence is limited to retrospective reviews regarding distraction injuries. Earlier classifications such as the Allen-­ Ferguson and the AO focus on mechanism of injury (distraction, compression, rotation) versus fracture morphology (compression, distraction, rotation), making it difficult to incorporate spinal stability and neurologic status and to determine the appropriate treatment. Cervical spine instability is best defined, by White and Panjabi,12 as the loss of the ability of the spine to maintain, under physiological loads, its pattern of displacement so that there is no initial or additional neurologic deficit, no major deformity, and no incapacitating pain. Subaxial instability has been characterized by 3.5-mm horizontal displacement or 11 degrees of adjacent vertebrae angulation on lateral radiographs. The Subaxial Cervical Spine Injury Classification (SLIC) integrates fracture morphology (compression, distraction, rotation), the diskoligamentous complex (DLC) integrity (stability), and neurologic status (intact, root, complete, or incomplete injuries).13 It has been shown to be reliable and valid, and to guide treatment appropriately14,15 (Table 9.1). All three characteristics have subgroups, assigning points to guide treatment; patients with scores ≤ 3 are treated nonoperatively, and patients with scores ≥ 5 are treated operatively. For patients with a score of 4, the treatment is guided by the surgeon’s experience and preference as well as the patient’s comorbidities and other injuries.

Evaluation The evaluation of a patient with spine trauma should follow the Advanced Trauma Life Support (ATLS) protocol, with immediate attention to a life-threatening airway compromise, ventilation (such as pneumothorax), and cardiovascular injury. Subsequent identification of

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Chapter 9 Table 9.1  Subaxial Cervical Spine Injury Classification (SLIC) System Finding Points Morphology   No abnormality  Compression  Burst   Distraction (e.g., facet perch, hyperextension)   Rotation/translation (e.g., facet dislocation, unstable teardrop, or advanced staged flexion   compression injury) Diskoligamentous complex (DLC)  Intact   Indeterminate (e.g., isolated interspinous widening, MRI signal change only)   Disrupted (e.g., widening of disk space, facet perch, or dislocation) Neurologic status  Intact   Root injury   Complete cord injury   Incomplete cord injury   Continuous cord compression in setting of neurologic deficit (neurologic modifier)

0 1 +1 = 2 3 4

0 1 2 0 1 2 3 +1

Source: Adapted from Vaccaro AR, Hulbert RJ, Patel AA, et al. The subaxial cervical spine injury classification system. A novel approach to recognize the importance of morphology, neurology, and integrity of the disco-ligamentous complex. Spine 2007;32:2365–2374

additional injuries, particularly neurologic or spinal injury, should be noted. A focused history should include identifying the trauma mechanism, determining the location of pain, and noting the presence of urinary incontinence, spondyloarthropathy (AS or DISH), or a pacemaker or other metallic foreign body that would contraindicate the use of MRI. The history should also note if the patient had undergone earlier spine surgery. Patients with ASD often have minimally displaced, nondisplaced, or missed fracture(s) that are often highly unstable (long lever arms from multifused segments) as a result of an extension-distraction mechanism. Such a fracture often is missed in the initial clinical and radiographic evaluation, but instability, neurologic compression, and symptomatic epidural hematoma (especially in a patient with coagulopathy) can lead to high rates of neurologic decline. The physical examination begins with complete exposure of the patient’s spine using a logroll technique. The dorsal spine is examined for ecchymosis, induration, or any other indicators of significant spine instability. Complete neurologic examination involves motor manual strength testing, sensory pinprick and light

touch evaluation, and reflexes with a careful rectal examination (for voluntary rectal tone, bulbocavernosus reflex, and anal wink reflex) to assess sacral nerve root function. The ASIA scale is the preferred neurologic examination tool, as it provides a method to characterize any residual function below the level of a spinal cord injury (SCI), which is defined as the most caudal level with normal motor and sensory function. The most important predictor of a favorable neurologic outcome is retention of sacral (S4-S5) sensation 72 hours to 1 week after the injury. Intact sacral pinprick sensation suggests a favorable prognosis for recovery of bladder function. In contrast, priapism caused by loss of sympathetic tone with unregulated parasympathetic input suggests a complete SCI. Neurologic status can be uncertain in polytrauma patients who are intubated, obtunded, or unable to follow commands. Serial neurologic exams are mandatory, with documentation of the neurologic examination as soon as possible. Complete disruption of neurologic function and neural impulse transmission in the torso and extremities can cause flaccid paralysis after SCI or can occur transiently during spinal shock.

Spinal shock ends with the return of the bulbocavernosus reflex, which indicates that the arc between the pelvic afferent nerves and sacral cord efferent nerves is once again functioning. Hemodynamic status should be carefully assessed to differentiate neurogenic from hypovolemic shock. To treat neurogenic shock and maintain mean arterial pressure above 85 mm Hg, volume resuscitation is followed by the use of vasopressors and chronotropic agents. The use of corticosteroids for a closed acute traumatic SCI is controversial. High rates of medical complications, the lack of consistent evidence, and a record of inconsistent neurologic recovery have limited the ability to formulate guidelines for the use of corticosteroids. Additionally, elderly patients with multiple comorbidities, morbidly obese patients, revision cases, polytrauma patients, and patients with suboptimal bone quality create more challenging surgical environments. Patients with SCIs must be promptly identified to decompress and realign spinal elements with prevention of secondary SCI due to ischemia. Flexion and extension distraction injuries are optimally managed by experienced spinal surgeons who are qualified to perform multiple fixation techniques and bailout strategies. In addition, optimal management requires ­facilities with the appropriate support staff trained in trauma surgery, anesthesia, neuromonitoring, and interventional neuroradiology, and that have an intensive care unit (ICU) whose staff is experienced in handling these types of cases.

Distraction (AO Type-B Injuries) as injuries can often be missed using only radiographs. CT and MRI are invaluable in identifying and understanding osseous fracture patterns, DLC and posterior ligamentous complex (PLC) integrity, degree and location of neurologic compression, anatomic variants, hematoma, and prior surgery (Figs. 9.2, 9.3, 9.4) Complete radiographic evaluation in light of the clinical scenario aids in formulating a full treatment plan. CT angiography (CTA) or magnetic resonance angiography (MRA) should be performed if a vertebral arterial injury is suspected and in patients with C1 and C2 fractures requiring surgical treatment, patients with fracture dislocations, and patients with fractures extending into the foramen transversarium given the higher rates of vertebral artery injuries. CT myelograms are useful in evaluating bony and neural anatomy when MRIs are contraindicated, and can give excellent detail of neural structures.

Imaging Cervical spine injuries require immediate evaluation and coordination with multiple services to adequately follow ATLS protocols. Once life-­ threatening injuries are diagnosed and stabilized, further cervical radiographic evaluation can proceed. Traditionally, anteroposterior (AP), lateral (Fig. 9.1), open-mouth odontoid, and swimmer’s lateral radiographic views were commonly ordered, but they have been largely replaced by initial cross-sectional imaging via multidetector helical computed tomography (CT) and magnetic resonance imaging (MRI),

Fig. 9.1  Lateral cervical radiograph demonstrating a C5–C6 flexion-distraction injury with 50% anterolisthesis in a patient with bilateral facet dislocation.

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Fig. 9.3  Midsagittal T2-weighted magnetic resonance imaging (MRI) demonstrating a C6–C7 flexion-distraction injury with anterior longitudinal ligament disruption, prevertebral edema, disk, posterior longitudinal ligament, and posterior ligamentous complex disruption.

Fig. 9.2  Midsagittal computed tomography (CT) image demonstrating a C6–C7 flexion-distraction injury with anterior subluxation, C7 superior end plate, and vertebral body fracture.

■■ Flexion-Distraction Injuries Flexion-distraction injuries (FDIs) represent severe injuries of the subaxial spine that begin with the PLC and facet joint and then lead to anterior disk disruption. Subsequent anterior subluxation of the cranial vertebrae (type I), with uncovering of the articular surfaces (naked facet sign on CT), progresses to unilateral (type II) or bilateral (type III, 50%) dislocation, with > 50% (type IV) dislocation being the last step. Many authors suggest that posterior longitudinal ligament (PLL) and disk disruption are

Fig. 9.4  Midsagittal CT reconstructed image in a patient with a C6–C7 extension-distraction injury in a patient with diffuse idiopathic skeletal hyperostosis (DISH) with flowing ossification of more than four consecutive vertebrae demonstrating anterior disk space widening, anterior column distraction, retropharyngeal widening, and hyperlordosis.

requisite for dislocation.6 Radiographs often demonstrate variable facet or interspinous process widening, disk space narrowing, facet fracture, subluxation, or dislocation (Fig. 9.1). CT best demonstrates the osseous anatomy and fractures, whereas MRI facilitates assessment of blood, the DLC (with short tau inversion recovery [STIR] sequence), and neural elements (cord signal change on T1 or T2 sequences) (Figs. 9.2 and 9.3). Progressive vertebral arterial occlusion and injury is related to increasing degrees of instability (rotation, translation, distraction) and are best evaluated with MRA or CTA. Due to the high degree of ligamentous injury, cervical FDIs are among the most unstable traumatic conditions, with neurologic injury ranging from 10 to 84%. Neurological manifestations include Injuries ranging from radiculopathy (in 70% unilateral perched facets, stage II) to complete SCI (up to 84% in bilateral dislocation, type IV). Spinal cord contusion (edema) or hemorrhage is best seen on MRI. In patients with FDIs, it is often difficult to obtain a closed reduction as well as maintain reduction via nonoperative measures (bedrest in traction, halo). Operative intervention is superior to nonoperative treatment unless patients cannot tolerate an operation.

Is Closed Reduction Safe? Closed reduction for cervical fracture subluxations has long been advocated in the treatment of subaxial FDIs due to early reduction and decompression of the neural elements. Class III evidence (cohort and case series) supports closed traction reduction in awake, alert, neurologically intact patients who can participate in serial neurologic examinations.16,17 However, neurologic worsening can occur in patients with bilateral facet fractures or stage IV FDI due to cord stretch or exacerbation due to unrecognized herniated nucleus pulposus (HNP).18 However, Vaccaro et al,17 in a prospective study with MRI pre- and postreduction, demonstrated no neurologic worsening, although the incidence of disk herniations increased after closed reductions. Pre-reduction MRIs are recommended in patients who are unable to be examined or in obtunded patients.

Distraction (AO Type-B Injuries) MRI is recommended after failed closed reduction or prior to surgical intervention. Based on moderate evidence, a strong recommendation for closed reduction is given for subaxial EDIs.

Is There a Role for Nonoperative Treatment in FDIs? Essentially there is no medical evidence to support external immobilization for cervical distraction injuries. A retrospective review (level IV evidence) of cervical fracture dislo­ cations suggests that external immobilization may be sufficient for < 1 mm displacement. In a prospective observational study, Lind ­utilized halo immobilization in 31 FDIs with 10 uni­lateral and seven bilateral dislocations, which ultimately resulted in four of 17 late subluxations requiring late surgery.19 Beyer’s retrospective comparative study showed better outcomes with surgery in unilateral facet-­ dislocations.20 Delay in definitive treatment and inability to obtain and maintain a reduction are common in patients treated externally. Very low quality evidence exists to support nonoperative management of FDIs; therefore, there is a weak recommendation for nonoperative management of subaxial FDIs with a halo vest in highly monitored settings.

How to Approach: Anterior, Posterior, or Combined? Although extensive reports exist, the quality of the published clinical evidence is low. Traditionally, FDIs were treated with posterior wiring and fusion after successful closed reductions.21 Failures were often related to fractured posterior elements (spinous process, lamina, or facet fractures). Biomechanically, lateral mass fixation is stronger than wiring techniques and less dependent on intact posterior elements. In irreducible injuries, anterior or posterior reduction with grafting and then posterior fixation with or without halo immobilization can be utilized. In general, expedient closed reduction is recommended for patients with cervical FDIs as described above. MRI should be obtained prior to operative intervention.17,18

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Chapter 9 If no HNP exists, posterior open reduction with or without partial removal of the caudal superior articular process followed by lateral mass fixation and fusion is appropriate, as posterior fixation with screws and rods has been shown to be biomechanically advantageous compared with anterior fixation. Late kyphosis and neck pain can occur after posterior only fixation and supplemental anterior cervical diskectomy and fusion (ACDF) may be considered. In a randomized prospective study, 24 patients with FDI and SCI were treated with either ACDF (n = 6) or posterior instrumentation with fusion (n = 18), yielding no difference in complications and in neurologic or radiographic outcomes.22 If an HNP is present, then anterior cervical diskectomy followed by anterior open reduction with either Caspar distraction pins or laminar spreaders is attempted (Fig. 9.5). If acceptable reduction is obtained in stage I and II injuries without end-plate or facet fractures, ACDF enables performing single-­ level constructs and may be preferable to posterior approaches.22 If anterior reduction cannot be obtained, then posterior reduction, lateral mass fixation, and fusion followed by subsequent anterior grafting and instrumentation is performed. In stage III or IV injuries, the PLL is disrupted and the instantaneous axis of rotation (IAR) shifts anteriorly. Anterior-alone fixation is inadequate, as no tension bands exists; however, posterior-only fixation entails the risk of additional anterior procedures being required due to kyphosis and late disk herniation. Overall, a strong recommendation for operative over nonoperative (halo, bed rest) treatment is given for cervical FDIs. Approach selection (anterior, posterior, or circumferential) is often dictated by surgeon and patient preference when closed reduction can be obtained. In stage I or II injuries without associated HNPs, it is a strong recommendation that posterior-only treatment is safe and effective. In stage I or II injuries with HNPs but without facet or end-plate fractures, anterior cervical diskectomy and fusion with plating is safe and effective. In stage III and IV injuries without associated HNPs or vertebral body fractures, it is a weak recommendation that posterior-only treatment is safe and effective. In stage III and

Fig. 9.5  Intraoperative lateral radiograph demonstrating laminar spreader used to effect anterior open reduction of a C4–C5 flexion distraction injury.

IV injuries with associated HNPs or vertebral body fracture, circumferential treatment is strongly recommended (Fig. 9.6).

■■ Extension-Distraction

Injuries

Extension-distraction injuries (EDIs) disrupt the anterior longitudinal ligament (ALL) and disk with or without the PLL or PLC. According to the Allen-Ferguson classification, these injuries are categorized as type I or type II based on whether there is anterior angulation/widening or subluxation, respectively. The PLL (acting as a tension band) has been thought to be the key structure differentiating the two types, although recent cadaveric studies suggest the facet capsules may be more important. Subsequent posterior translation of the cranial verte-



Distraction (AO Type-B Injuries) the treatment of subaxial FDIs and EDIs. Class III evidence (cohort and case series) supports the use of closed reduction maneuvers so long as excessive flexion positioning is not required. Although closed reduction has been found to be safe for patients with EDIs, a high failure rate has been noted in patients with facet fractures due to possible overdistraction.16,17 Neurologic worsening has been postulated to be due to overdistraction, noncontiguous unrecognized cranial injuries, herniated nucleus pulposus, hematoma, and cord edema. Based on moderate evidence, a strong recommendation for closed reduction is given for subaxial EDIs.

Is There a Role for Nonoperative Treatment in EDIs? Fig. 9.6  Postoperative intraoperative lateral radiograph demonstrating circumferential fusion of a C4–C5 flexion-distraction injury.

brae results in canal stenosis with or without cord compression. Radiographs often demonstrate anterior retropharyngeal soft tissue swelling, disk space widening, and anterior osteophyte avulsion fractures. Often, radiographs and CT may not demonstrate any radiological abnormalities and subluxation or dislocation. CT best determines osseous anatomy and fractures, whereas MRI facilitates assessment of the DLC (on STIR sequences) and neural elements (cord signal change on T1 or T2 sequences) (Fig. 9.4). In patients with AS or DISH, MRI is essential to identify subtle fractures or hematomas, even in neurologically intact patients, which greatly affect management. Hyperextension injuries commonly cause significant neurologic injury (often central cord syndrome) due to sagittal canal narrowing during extension, often in elderly patients with underlying cervical stenosis.

Is Closed Reduction Safe? As described above, closed reduction for cervical fracture subluxations has been utilized in

Halo immobilization after closed reduction has been shown to be safe and effective in selected well-reduced EDIs.16 Very low quality evidence supports halo immobilization of EDIs; therefore, there is a weak recommendation for halo management of subaxial EDIs if neutral cer­ vical flexion can be obtained and maintained with avoidance of hyperflexion. A key point must be emphasized: the above reviews and subsequent recommendation exclude patients with AS or DISH (see below).

How to Approach: Anterior, Posterior, or Combined? Retrospective reports (low overall quality of evidence) support anterior or posterior fixation as well as combined approaches depending on the overall stability of the injury primarily related to PLC disruption. Vaccaro et al23 report that patients with stage I EDIs (disruption of the ALL, disk, and PLL without PLC or posterior element disruption or translation) can be successfully managed with anterior tension band plating or fixation only due to isolated anterior or middle column disruption. Type II injuries are more complex and typically require posterior fixation to obtain stability. A weak recommendation for anterior-alone fixation in type I injuries is appropriate. A strong recommendation against anterior-alone fixation for type II

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Chapter 9 injuries with the use of posterior instru­ mentation to provide adequate stabilization is appropriate.

■■ Ankylosing Spondylitis and

Diffuse Idiopathic Skeletal Hyperostosis

Ankylosing spondylitis is a chronic inflam­ matory disease with progressive sacroiliac and axial skeletal joint involvement that is most prevalent in males (3:1) often presenting in the second or third decades. Ninety percent of AS are associated with the human leukocyte antigen (HLA) B27 laboratory marker (compared with 7% of the general population). Extra-­ articular manifestations include anterior uveitis, carditis, aortitis, conduction defects, rest lung disease or fibrosis, ileitis/colitis, and renal failure. It affects cartilage, bone, and synovial joints, often progressing from enthesitis and synovitis to chondritis and osteitis. AS ossification (marginal syndesmophytes) occurs typically caudally to cranially (sacroiliac joints initially, cervical lastly) with the bridging between vertebrae occurring in line with the margins of the body (“bamboo spine”). Diffuse idiopathic skeletal hyperostosis (DISH) is a common disorder of unknown etiology (affecting up to 28% of patients aged > 60 years). Given the increasing size of the aging population combined with the increasing occurrence of type 2 diabetes mellitus and obesity, DISH is more frequently being diagnosed. Potential sequelae of hyperostosis in the cervical spine include stenosis, dysphagia, cervical myelopathy, and SCI resulting from even minor trauma. The incidence of delayed neurologic injury due to fracture is high as a result of unrecognized instability. Extraspinal manifestations are numerous and include an increased risk of heterotopic ossification after total hip arthroplasty. DISH is more common in patients with diabetes mellitus and gout. DISH is recognized radiographically by the presence of “flowing” ossification along the anterolateral margins of

at least four contiguous vertebrae and the absence of changes of spondyloarthropathy or degenerative spondylosis. A recent systematic review by Westerveld et al24 reported similar findings but also emphasized that surgical or nonoperative treatment did not alter the neurologic prospective for most patients. They found that the complication rate was 51.1% in AS patients and 32.7% in DISH patients. The overall mortality within 3 months after injury was 17.7% in AS and 20.0% in DISH. This review mirrors the existing retrospective literature suggesting that the clinical outcome of patients with fractures in previously ankylosed spines, due to AS or DISH, is considerably worse compared with the general trauma population.25

Do All AS or DISH Patients Need Advanced Imaging? Patients with ASD most commonly also have AS or DISH. Both disorders create a stiff spine that is often fused and functionally restricted with underlying osteoporotic bone. Fractures are up to three to four times more prevalent than in the general population. Delay in diagnosis is unfortunately common and can be catastrophic due to neurologic injury and deterioration often resulting from epidural hematoma. Plain radiographs alone are not appropriate. CT is mandatory in evaluation of these patients, and MRI best identifies subtle transverse fractures associated with edema and posterior element disruption. Although many reports advocate caution and judicious evaluation, diagnosis, and treatment of patients with ASD, the quality of the literature is low to very low, as these reports are retrospective case series and reviews. Caron et al’s26 retrospective review of 112 ASD patients with fractures found that a delay in diagnosis, neurologic decline (81%), and a high risk of complications and death (threefold increase or 20 to 30%) are unfortunately common. Due to the increased risk of neurologic decline and mortality, a strong recommendation is given that patients with ASD undergo CT and MRI (unless contraindicated).



Do All AS or DISH Patients Need Operative Treatment for Cervical Fractures? Although a few older case reports or case ­series support nonoperative management of cervical fractures in patients with ASD, modern reports, though retrospective (low overall quality of evidence), overwhelmingly favor operative management.25,27 As described above regarding the optimal operative approach to EDIs, AS and DISH patients are best stabilized with a posterior approach with multiple fixation points above and below the fracture. Short segment instrumentation to spare segments is not of concern. We strongly recommend operative intervention via multilevel posterior segmental constructs to provide adequate stabilization to allow fracture healing with supplemental anterior void grafting as needed.26

■■ Chapter Summary Cervical subaxial flexion and extension distraction fractures are typically unstable and severe injuries that are often associated with high rates of neurologic injury, morbidity, and mortality. Delay in diagnosis is common in patients with ankylosing spinal disorders, and advanced imaging is required. Prompt closed

Distraction (AO Type-B Injuries) reduction followed by surgical management is typically required to provide a stable environment to enable fracture healing, to maximize neurologic recovery and function, and to minimize complications. Pearls ◆◆ Integration of fracture morphology and diskolig-

amentous and neurologic status is necessary to guide treatment of subaxial fractures. ◆◆ Magnetic resonance imaging is necessary for appropriate diagnosis of cervical distraction injuries, especially in patients with DISH or AS, because missed injuries can have dire consequences. ◆◆ Closed reduction is recommended for cervical subaxial distraction injuries in awake, alert patients who can participate in serial neurologic examinations. ◆◆ Cervical distraction injuries are highly unstable, and operative treatment is recommended for most cervical distraction injuries. The selection of an approach is a complex process, often in­ fluenced by the presence or absence of disk herniation. Pitfalls ◆◆ Failing to identify and decompress cervical disk

herniations prior to reduction in patients failing closed, awake reductions. ◆◆ Missing extension distraction injuries in DISH or AS patients.

References

Five Must-Read References 1. Joaquim AF, Patel AA. Subaxial cervical spine trauma: evaluation and surgical decision-making. Global Spine J 2014;4:63–70 PubMed 2. Tee JW, Chan CH, Fitzgerald MC, Liew SM, Rosenfeld JV. Epidemiological trends of spine trauma: an Australian level 1 trauma centre study. Global Spine J 2013;3:75–84 PubMed 3. Koivikko MP, Myllynen P, Santavirta S. Fracture dislocations of the cervical spine: a review of 106 conservatively and operatively treated patients. Eur Spine J 2004;13:610–616 PubMed 4. Colterjohn NR, Bednar DA. Identifiable risk factors for secondary neurologic deterioration in the cervical spine-injured patient. Spine 1995;20:2293–2297 PubMed

5. France JC, Bono CM, Vaccaro AR. Initial radiographic evaluation of the spine after trauma: when, what, where, and how to image the acutely traumatized spine. J Orthop Trauma 2005;19:640–649 PubMed 6. Vaccaro AR, Madigan L, Schweitzer ME, Flanders AE, Hilibrand AS, Albert TJ. Magnetic resonance imaging analysis of soft tissue disruption after flexion-distraction injuries of the subaxial cervical spine. Spine 2001;26:1866–1872 PubMed 7. Stassen NA, Williams VA, Gestring ML, Cheng JD, Bankey PE. Magnetic resonance imaging in combination with helical computed tomography provides a safe and efficient method of cervical spine clearance in the obtunded trauma patient. J Trauma 2006;60: 171–177 PubMed

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Chapter 9 8. Wright JG, Swiontkowski MF, Heckman JD. Introducing levels of evidence to the journal. J Bone Joint Surg Am 2003;85-A:1–3 PubMed 9. Atkins D, Best D, Briss PA, et al; GRADE Working Group. Grading quality of evidence and strength of recommendations. BMJ 2004;328:1490 PubMed 10. West S, King V, Carey TS, et al. Systems to Rate the Strength of Scientific Evidence. Evidence Report/ Technology Assessment No. 47 (Prepared by the Research Triangle Institute–University of North Carolina Evidence-Based Practice Center, Contract No. 290–97–0011). Rockville, MD: Agency for Healthcare Research and Quality; 2002 11. Norvell DC, Dettori JR, Skelly AC, Riew KD, Chapman JR, Anderson PA. Methodology for the systematic ­reviews on an adjacent segment pathology. Spine 2012;37(22, Suppl):S10–S17 PubMed 12. White AA 3rd, et al., Biomechanical analysis of clinical stability in the cervical spine. Clin Orthop Relat Res 1975;109:85–96 13. Vaccaro AR, Hulbert RJ, Patel AA, et al; Spine Trauma Study Group. The subaxial cervical spine injury classification system: a novel approach to recognize the importance of morphology, neurology, and integrity of the disco-ligamentous complex. Spine 2007;32: 2365–2374 PubMed 14. Dvorak MF, Fisher CG, Fehlings MG, et al. The surgical approach to subaxial cervical spine injuries: an evidence-based algorithm based on the SLIC classification system. Spine 2007;32:2620–2629 PubMed 15. Whang PG, Patel AA, Vaccaro AR. The development and evaluation of the subaxial injury classification scoring system for cervical spine trauma. Clin Orthop Relat Res 2011;469:723–731 PubMed 16. Rockswold GL, Bergman TA, Ford SE. Halo immobilization and surgical fusion: relative indications and effectiveness in the treatment of 140 cervical spine injuries. J Trauma 1990;30:893–898 PubMed 17. Vaccaro AR, Falatyn SP, Flanders AE, Balderston RA, Northrup BE, Cotler JM. Magnetic resonance evaluation of the intervertebral disc, spinal ligaments, and spinal cord before and after closed traction reduction of cervical spine dislocations. Spine 1999;24:1210– 1217 PubMed

18. Eismont FJ, Arena MJ, Green BA. Extrusion of an intervertebral disc associated with traumatic subluxation or dislocation of cervical facets. Case report. J Bone Joint Surg Am 1991;73:1555–1560 PubMed 19. Lind B, Sihlbom H, Nordwall A. Halo-vest treatment of unstable traumatic cervical spine injuries. Spine 1988;13(4): 425–432 20. Beyer CA, Cabanela ME, Berquist TH. Unilateral facet dislocations and fracture-dislocations of the cervical spine. J Bone Joint Surg Br, 1991;73(6):977–981 21. Bohlman HH. Acute fractures and dislocations of the cervical spine. An analysis of three hundred hospitalized patients and review of the literature. J Bone Joint Surg Am 1979;61:1119–1142 PubMed 22. Brodke DS, Anderson PA, Newell DW, Grady MS, Chapman JR. Comparison of anterior and posterior approaches in cervical spinal cord injuries. J Spinal Disord Tech 2003;16:229–235 PubMed 23. Vaccaro AR, Klein GR, Thaller JB, Rushton SA, Cotler JM, Albert TJ. Distraction extension injuries of the cervical spine. J Spinal Disord 2001;14:193–200 PubMed 24. Westerveld LA, Verlaan JJ, Oner FC. Spinal fractures in patients with ankylosing spinal disorders: a systematic review of the literature on treatment, neurological status and complications. Eur Spine J 2009;18: 145–156 PubMed 25. Whang PG, Goldberg G, Lawrence JP, et al. The ­management of spinal injuries in patients with ankylosing spondylitis or diffuse idiopathic skeletal hyperostosis: a comparison of treatment methods and clinical outcomes. J Spinal Disord Tech 2009;22: 77–85 PubMed 26. Caron T, Bransford R, Nguyen Q, Agel J, Chapman J, Bellabarba C. Spine fractures in patients with ankylosing spinal disorders. Spine 2010;35:E458–E464 PubMed 27. Bransford RJ, Koller H, Caron T, et al. Cervical spine trauma in diffuse idiopathic skeletal hyperostosis: injury characteristics and outcome with surgical treatment. Spine 2012;37:1923–1932 PubMed

10 Facet and Lateral Mass Fractures Máximo-Alberto Díez-Ulloa

■■ Introduction Fractures of the lateral mass and facets may occur in complex injuries and lead to very unstable scenarios, which are addressed in other chapters. This chapter discusses isolated lateral mass and facet fractures of the subaxial (C3-C7) cervical spine. The atlas and the axis have two lateral masses each, but injury to these structures is more relevant to the occipito-atlantoaxial complex, has been described previously.

■■ Definition Bono et al,1 in their subaxial cervical injury description (SCID) system, describe a lateral mass fracture as “the fracture of any portion of the lateral mass complex, including the articular processes and the pedicle.” This categorization includes the so-called floating lateral mass, in which ipsilateral fractures of the lamina and pedicle result in the whole lateral mass, with both facet joints, in discontinuity the rest of the vertebra, bringing about a facet subluxation with both the upper and lower vertebrae and a mechanically very unstable scenario. Bono et al’s study focused on the discrepancies in the description of cervical injuries by expert surgeons. The main conclusion was that spine surgeons often disagree in the evaluation

of the same images. Lateral mass fracture, however, was ranked highest in surgeon agreement among 11 proposed entities, reaching 70%, which is quite good, but not complete agreement.

■■ Cervical Spine Anatomic

Considerations

Anatomically, either of the two lateral masses at a specific functional spinal segment, including its two facet joints, is considered one of the four columns (one on each side) of the cervical spine.2 This columnar structure should not be seen in the same way of the Denis concept of columns, but refers instead to the bony architecture, with the four columns being the vertebral body, the two lateral masses, and the posterior arch (laminae and spinous process). In the Cervical Spine Injury Severity Score (CSISS) system, injuries to a lateral mass that are equal in specific weight to the injuries to vertebral body and the two lateral masses account for 50% of the total score. In between the upper cervical spine (occipital-C1-C2) that works mainly in rotation (besides extension at occiput-C1), and the lower cervical spine (C4-C7) that does it mostly in flexion extension; a middle cervical spine (C3C4) has been described.3. The pathoanatomy of such middle segment of the cervical spine would be characterized by shear injuries with



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Chapter 10 soft tissue involvement but scarcity of bone injury, whereas injuries from C4 to C7 generally involve bony structures, especially the vertebral body and the lateral masses.

in the context of a flexion-distraction injury.5 Facet fractures, in contrast, are usually the result of a flexion injury with a rotational component, although sometimes they may occur in axial-compression injuries6 (Figs. 10.1, 10.2, 10.3).

■■ Mechanism of Injury It is necessary to differentiate between lateral mass fractures and facet injuries. Injury to the pars interarticularis or the main body of the lateral mass is generally of the extension type, in combination with either compressive4 or distractive forces. Infrequently, it may also occur

■■ Classification There is a lack of clarity regarding the definition of cervical injuries. Bono et al1 published the results of an expert consensus on specifying the type of injury as a first step in making

a

b

c

d

Fig. 10.1a–d  Patient who was injured in a motor vehicle accident was diagnosed with (a) a C4 left lateral mass, (b) a C5 burst fracture with a sagittal fracture line, (c) a C4 listhesis, with (d) the characteristic horizontalization of the floating lateral mass.

In addition, there is a C3 inferior left facet fracture. Both an extension type (C4) and a flexion type (C5) injuries occurred at adjacent segments, probably from a global C-spine axial compression injury. The patient had no neurologic symptoms.



Facet and Lateral Mass Fractures

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as spondylolysis (uni- or bilateral) or as split, comminuted, and floating lateral mass (both pedicle and ipsilateral lamina fractures, also referred to as “separation type”), whereas a facet fracture can be further categorized based on whether or not the facets are dislocated4,7 (see text box). Classification of Lateral Mass/Facet Fractures

Fig. 10.2  Magnetic resonance imaging of the same patient as in Fig. 10.1.

management recommendations. Transitional forms of injury also exist. Lateral mass injuries have been classified in two major types7: lateral mass and facet injury. Lateral mass injuries can be further categorized

1. Lateral mass a. Spondylolysis i. Unilateral ii. Bilateral b. Comminuted c. Split i. Sagittal ii. Coronal iii. Transverse d. Separation (floating mass) 2. Facet joint a. Facet fracture b. Facet dislocation 3. Mixed or other type Example: lateral mass with contralateral lamina fracture Modified from Kotani et al4 and Lee and Sung.7

a

b

Fig. 10.3a,b  Patient was treated with anterior cervical diskectomy and fusion C3-C6. (a,b) Postoperative radiographs. She has a 5 years follow-up with an excellent clinical outcome



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a

b

Fig. 10.4a,b  (a) Intraoperative image of a unilateral approach for a unilateral facet fracture-dislocation with radiculopathy C7 at left C6-C7. Note the

amount of dissection that was needed. (b) Post­ operative radiograph. He has a 6-year follow-up with an excellent outcome.

There are slight differences in the descriptions of these injuries in the literature. Kotani et al4 do not include isolated facet injuries in their study, and concept of split injuries refers only to the coronal plane with impaction of fragments. Lee and Sung,7 on the other hand, consider only unilateral spondylolysis. We therefore use a compound classification, adding the always useful “mixed” or “other” type to account for injuries that a surgeon might consider to be a lateral mass fracture but that do not entirely match any of the proposed types. These facet fractures, especially of the superior facet, may be associated with soft tissue injury at the annulus of the disk, the ipsilateral facet joint capsule, and the flavum, giving rise to a unilateral facet fracture dislocation, with mainly a rotational component. It must be noted that rotation and lateral flexion are a coupled motion in this anatomic region (subaxial cervical spine); one cannot occur isolated from the other: whenever there is a rotation, some lateral flexion takes place and vice versa. These fracture dislocations may be somewhat more stable than the unilateral facet dislocations, as the injury to the annulus might be less pronounced. However, it is not always clear how to differentiate between these types of injuries. Theoretically, they can be considered as somewhat different entities, with the pure unilateral dislocation being the more unstable injury, requiring more energy dissipation and then more extensive injury to the disk and other

structures (even the contralateral facet capsule) rendering it less stable once it is reduced than the facet fracture-dislocation and less stable on presentation, but with less soft tissue damage, and therefore easier to manage with only unilateral osteosynthesis8 (Fig. 10.4).

■■ Pathoanatomy Musculoskeletal Level of Injury Lateral mass and facet fractures are typically a lower cervical spine injury. There is, again, some difficulty in reviewing the cases from several series in the literature, as some injuries are described based on the functional spinal unit that was affected and fused, and others are described based on the specific vertebra that was injured. As we will discuss below, most of the time a C6 lateral mass fracture ­requires C6-C7 surgery, but if we are dealing with a superior articular facet fracture it may require C5-C6 surgery. As a general rule, the lower the level, the higher the incidence of lateral mass fracture in the subaxial cervical spine.4,5,8 Nevertheless, Lee and Sung,7 in their clinical series that included isolated facet fractures, report a peak incidence at C4. This is in contrast with the concept of the middle cervical spine segment

in which Torg et al3 found no bone injury but only soft tissue injury, which perhaps can be explained by the fact that their report is a study of a cadaveric model, not a clinical series. They also report that this injury occurred in axial compression, whereas as stated above, these injuries occur mostly from an extension type of mechanism, but also sometimes from flexion-­ distraction forces4,5

Soft Tissue Involvement at the Injured Level Kotani et al4 report that in lateral mass fractures, the instability and the soft tissue injury mainly occur in the caudal functional spinal unit (C6C7 for a C6 lateral mass fracture); thus, in these lateral mass fractures the instability usually happens opposite to isolated facet fractures (generally the cranial cranial one in the mass: C5C6 for a C6 facet fracture). So, there is some degree of anterolisthesis in more than 75% of cases of lateral mass injuries (inferior level instability) but in only 33% of facet fractures; in this latter injury scenario (facet fracture), the superior level is displaced instead most frequently (50% of cases), superior level instability. Similarly, in lateral mass fractures up to 75% of cases had an anterior longitudinal ligament (ALL) injury, and the same percentage had a disk injury, as seen on magnetic resonance imaging (MRI), with anterolisthesis of the fractured vertebra; 25% of cases also showed some ALL involvement and anterolisthesis of the vertebra above the fracture level. The ALL was injured in all split-type cases and in a high percentage of every other type of lateral mass fracture; comminution and separation occurred less often (50% and 60%, respectively). The disk was affected in 50% of each type of injury; it was affected the least in unilateral spondylolysis (30%). The posterior longitudinal ligament (PLL) was injured in 30 to 50% of cases, mostly in split and facet fractures without dislocation, with the exception of the comminution type, in which the PLL was never injured. In facet fractures, the displacement (and thus the instability) is mostly at the cranial adjacent vertebra, with a high (80%) incidence of disk injury and the absence of injury in the

Facet and Lateral Mass Fractures posterior ligamentous complex. Nevertheless, these data should be considered cautiously because an injury to the tissue does not imply that there is mechanical instability necessitating surgical stabilization. A rotational instability (> 10 degrees) entails a split and unilateral facet fracture-dislocation; a sagittal instability (kyphotic segment > 10 degrees) entails a split fracture and translational instability (> 3.5 mm) in split, unilateral facet fracture-dislocation and comminution, and sometimes in the separation type of injury.7 It is noteworthy that the split type refers to a coronal split with impacted facets in this series, but even in a sagittally oriented split lateral radiographs demonstrate spine malalignment in up to 66% of patients.9 Yetkin et al10 reported that in pillar fractures the uncovertebral joint appear widened on anteroposterior views, which could be explained by rotational malalignment at the segment. Thus, lateral mass fractures may frequently lead to unstable configurations even without concomitant soft tissue injury, carrying the risk of mechanical instability in the form of bony structural failure. In separation-type injuries (such as a floating mass), there is not only a lateral subluxation of the affected mass but also a horizontalization of it (rotation in the sagittal plane, with the cranial facet leaning forward (ventrally) and the caudal facet dorsally). These considerations explain why surgical management is usually necessary (see below).

Associated Neurovascular Injuries These fractures frequently have associated neurovascular injuries, especially root symptoms, both paresthesias and weakness,5 and less frequently vertebral artery injuries, due to the close proximity of both the nerve root and the vertebral artery to the lateral mass. As the foramen through which the root leaves the spinal canal is formed partly by the lateral mass and the facet, even minor intrusion by bone fragments may cause impingement and radicular damage. The vertebral artery courses through a canal between the vertebral body and the transverse processes, so displacements that entail

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Chapter 10 listhesis always pose a risk. Furthermore, the bony foramen transversarium is also quite snug around the vessel, so that any invasion or displacement into it may cause vascular injury.

Root and Spinal Cord Injury In a series of undisplaced facet fractures,5 70% of patients had referred pain “at the level of the neck, shoulder, arm or chest,” and 56% complained of some sensory radiculopathy and 40% of some muscle weakness. In the series of Lee and Sung,7 there was a 36% incidence (14/39) of concomitant cord injury (half of them in patients with fractured facet), two thirds of which was American Spinal Injury Association (ASIA) grade C or more severe; radiculopathy was present in 44% of patients. It is easy to understand that in displaced cases, especially if the superior facet is involved, the incidence of radiculopathy would increase dramatically. In my own experience, some form of root involvement was present in almost every patient with facet injury.

Vertebral Artery Injury The vertebral artery lies in close anatomic relationship with the lateral mass, side by side with the lateral wall and tied to the spine when it crosses through the foramen transversarium, between the remnants of the rib and the transverse process itself. Fortunately, there is a low incidence of clinically significant injuries of the vertebral artery. The overall incidence of blunt trauma is 17% in patients with cervical injuries (as seen on multidetector computed tomography [CT] angiogram). The incidence of secondary neurologic events is 14% in patients with a vertebral artery injury (VAI), and the incidence of stroke-related mortality is 5% (two of 42 patients with VAIs among a total series of 253 multidetector CT angiogram-tested patients after cervical injury from blunt trauma). Lee and Sung7 reported two cases of vertebral artery dissection among 39 patients. There was a correlation between VAI and fracture displacement into the foramen transversarium > 1 mm (adjusted odds ratio [OR], 3.29; p = 0.026) by

multivariate regression model (together with a basilar skull fracture), but more relevant to our discussion was the association between facet subluxation/dislocation and neurologic event (crude OR, 9.0; p = 0.004). In addition, the diagnosis of ankylosing spondylitis/diffuse idiopathic skeletal hyperostosis had a high ­association with VAI (OR, 8.04; p = 0.034) by univariate analysis and an association with neurological events (OR, 40.67; p < 0.001).11 An analysis of the patterns of cervical spine fracture-dislocations in VAI found that distraction was the main etiopathogenic factor, with facet dislocation, with or without fracture, being the most common pattern, and C5 being the most frequently injured level. Again, displacement into the foramen transversarium was present in almost half of the patients.12 In a series of 69 suspected VAIs in patients with facet dislocation or fractures extending to the foramen transversarium in the cervical spine, 19 (27.5%) had an actual injury. There was a 21% incidence of vertebrobasilar ischemia (4/19), with two deaths at 4 and 21 days. Almost half of the patients had a spine injury that was deemed unstable and required surgery.13 Most VAI patients remain asymptomatic (Fig. 10.5). The major mechanisms of injury are distraction (either extension or flexion) and lateral flexion. The vascular injury pattern usually is dissection or occlusion. Digital subtraction angiography (DSA) is the most sensitive imaging technique for these cases, but its invasiveness makes it questionable as a screening method. Magnetic resonance angiography can also diagnose VAI, without entailing the invasiveness of DSA. Management includes (1) interventional neuroradiology for hemorrhagic VAI and progressive vertebrobasilar stroke, and (2) systemic anticoagulation with heparin for mild ischemia. Controversy exist about the management of asymptomatic patients because the natural history of VAI has not been described in this context; however, both prophylactic heparin and antiplatelet agents have been advocated, which might interfere with performing early surgery.14 The incidence of VAI can increase to 50% in midcervical spine fracture or subluxation,15 probably related to the tendency for



Fig. 10.5  A 19-year-old patient who was injured in a motor vehicle accident presents with a fracture at C3 and a left lateral mass with involvement of the pedicle and left unciform facet with a rotational shear transverse component. The patient remained asymptomatic and was treated with antiaggregants and rigid external immobilization.

translational injuries in this area due to soft tissue damage, as previously described.3 As for the topography of these lesions, occlusion at its origin or at the injured level is the most frequent injury pattern. The artery on the left side is more frequently affected.15 The findings in a series of six cases suggest that early surgery might stabilize the clot after embolization.16 This can be an additional argument for surgical stabilization.

■■ Treatment Treatment is guided by the type of injury, the presenting symptoms (note the presence of root injuries or VAIs), and the associated injuries in the musculoskeletal system (cervical spine, other areas of the spine, long bones, pelvis, etc.) or in other systems. There is a considerable incidence of concomitant injuries to the central nervous system, respiratory system, and intra-abdominal organs.5 Lateral mass fractures entail a double-joint injury, which implies a chain injury in which two consecutive links are damaged, and four

Facet and Lateral Mass Fractures articular surfaces are compromised for sub­ sequent incongruity. Thus, the first priority of treatment is mechanical stability, and the second is the maintenance of the key spatial relationship between the articular cartilages in the synovial joint to avoid posttraumatic degenerative changes. Surgical treatment is usually preferred for these injuries, except for some undisplaced facet fractures (see below) and for unilateral undisplaced spondylolysis. Floating mass (separation) (Fig. 10.6) and comminution-type lateral mass fractures are the most unstable situations. Stability of spondylolysis-type fractures depends on the remaining soft tissue injury (comparable to the hangman type of axis fractures). The split type of fracture may lead to a painful joint, depending on the displacement, with resulting subluxation and joint incongruency. Depending on the instability pattern, caudal-­ evel stabilization is usually necessary. There is, however, no consensus on whether this should be done through an anterior or a posterior approach. The posterior approach has some ­ biomechanical advantages and provides direct access to the root decompression, whereas the anterior approach eliminates any problem arising from the disk tissue and generally results in a more lordotic spine alignment and a lower incidence of local pain from muscle dissection. In the floating mass (separation) (Fig. 10.6) and comminution types of injuries, a two-­ level arthrodesis is preferable, although if the comminution is slight and without displacement, or if MRI shows a pristine upper level, one-level (inferior) surgery might be considered4; however, with anterior fusion, one-level surgery in separation types of injuries sometimes yields an unsatisfactory outcome.7 As a general rule, surgical treatment is preferred in isolated facet injuries, even in undisplaced facet fractures.5 In addition to local instability, there is articular incongruence if the articular surfaces are damaged (split type, sagittal or coronal, or comminution type). Nevertheless, conservative treatment can be considered in superior facet fractures (the most common) if there is enough of the facet joint left to prevent displacement. Spector et al17

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a

b

c

d

Fig. 10.6a–d  Patient presented with a separation-­ type fracture (floating mass) at C4 on the left side at the caudal level. Treatment entailed one-level surgery (C4-C5). (a) Admission lateral radiograph.

(b) Computed tomography axial scan. (c) Anteroposterior radiograph at 5-year follow-up. (d) Lateral radiograph at 5-year follow-up.

suggest that if the fracture line lies higher than 40% of the facet height, this is, the fracture fragment is less than 60% of the facet height or if its absolute vertical height is less than 1 cm, then the facet remnant that remains attached to the

lateral mass is sufficient to maintain segmental stability. However, one should consider that the ALL and the disk are injured at the inferior level in about two thirds of patients and at the upper level in one fourth to one third of patients.4

In choosing between an anterior or a posterior approach, a careful evaluation of the disk is mandatory. If there is radiculopathy at the level of injury, anterior distraction has been reported to open the foramen, but if there is a displaced facet fracture it might be more convenient to perform a direct root decompression via a posterior approach.8

■■ Chapter Summary The lateral mass as an anchorage column of the cranial and caudal facet joints is a crucial load-bearing structure. We can categorize the injuries in these structures as lateral mass body or pars interarticularis fractures and facet injuries. The former are caused mostly by extension mechanisms, whereas the latter are caused by rotation mechanisms. Some undisplaced facet fractures, such as a small “tip” fracture or unilateral stable spondylolysis, can be treated nonsurgically. Usually there are accompanying soft tissue injuries, especially at the caudal functional spinal unit (e.g., C6-C7 for a C6 lateral mass fracture), that render the segment unstable to some extent. In these cases surgical stabilization is indicated. Surgery can be performed from either an anterior or a posterior approach. In general, anterior reconstruction achieves better kyphosis correction and has fewer complications ­entailing pain or infection, whereas posterior instrumentations (screws and rods) render a more mechanically stable scenario and can include a root decompression under direct visualization if needed. The choice of approach also

Facet and Lateral Mass Fractures depends on the injured structures. If there is a severe disk injury, the anterior approach is preferable. One-level surgery is possible either from an anterior (some separation and almost any other lateral mass type except comminution) or a posterior approach. In comminution or displaced split types of injuries, two-level surgical stabilization should be considered. Pearls ◆◆ For the majority of lateral mass fractures, surgical

stabilization is indicated.

◆◆ If there is substantial injury to the caudal level,

◆◆

◆◆

◆◆ ◆◆

◆◆

consider surgery even in nondisplaced facet fractures. Asymmetry between joints as seen on anteroposterior radiographs or coronal CT reconstructions are signs of mechanical instability. A superior facet fracture with radicular symptoms and an intact contralateral joint can be treated posteriorly and unilaterally. If there is a clear and serious disk injury, choose an anterior approach. Carefully review the injury pattern and the damaged structures to decide whether surgery is needed; if it is, determine which approach to use and how many levels need to be treated. Consider the possibility of a vertebral artery injury, especially if the foramen transversarium is involved or in ankylosing diseases.

Pitfalls ◆◆ Failure to diagnose facet and lateral mass frac-

tures in a polytrauma patient.

◆◆ Initial radiograms should include lateral projec-

tions. If the radiograms are inconclusive, obtain CT scans with multiplanar reconstructions. ◆◆ Consider a facet fracture as stable just because it is undisplaced.

References

Five Must-Read References 1. Bono CM, Schoenfeld A, Gupta G, et al. Reliability and reproducibility of subaxial cervical injury description system: a standardized nomenclature schema. Spine 2011;36:E1140–E1144 PubMed 2. Patel AA, Vaccaro AR, Anderson PA. Classification of cervical spine injury. In: Bridwell KH, DeWald RL, eds.

The textbook of spinal surgery, 3rd ed. Philadelphia: Lippincott Williams & Wilkins; 2011:1381–1389 3. Torg JS, Sennett B, Vegso JJ, Pavlov H. Axial loading injuries to the middle cervical spine segment. An analysis and classification of twenty-five cases. Am J Sports Med 1991;19:6–20 PubMed

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Chapter 10  4. Kotani Y, Abumi K, Ito M, Minami A. Cervical spine injuries associated with lateral mass and facet joint fractures: new classification and surgical treatment with pedicle screw fixation. Eur Spine J 2005;14:69– 77 PubMed  5. Aarabi B, Mirvis S, Shanmuganathan K, et al. Comparative effectiveness of surgical versus nonoperative management of unilateral, nondisplaced, subaxial cervical spine facet fractures without evidence of spinal cord injury: clinical article. J Neurosurg Spine 2014;20:270–277 PubMed 6. Ivancic PC. Biomechanics of sports-induced axial-­ compression injuries of the neck. J Athl Train 2012; 47:489–497 PubMed  7. Lee SH, Sung JK. Unilateral lateral mass-facet fractures with rotational instability: new classification and a review of 39 cases treated conservatively and with single segment anterior fusion. J Trauma 2009;66: 758–767 PubMed 8. Ulloa MA. Unilateral facet dislocations with radiculopathy: one side is enough. Proc Global Spine Congress 2013;A222 9. Lee C, Woodring JH. Sagittally oriented fractures of the lateral masses of the cervical vertebrae. J Trauma 1991;31:1638–1643 PubMed 10. Yetkin Z, Osborn AG, Giles DS, Haughton VM. Uncovertebral and facet joint dislocations in cervical articular pillar fractures: CT evaluation. AJNR Am J Neuroradiol 1985;6:633–637 PubMed

11. Lebl DR, Bono CM, Velmahos G, Metkar U, Nguyen J, Harris MB. Vertebral artery injury associated with blunt cervical spine trauma: a multivariate regression analysis. Spine 2013;38:1352–1361 PubMed 12. Gupta P, Kumar A, Gamangatti S. Mechanism and patterns of cervical spine fractures-dislocations in vertebral artery injury. J Craniovertebr Junction Spine 2012;3:11–15 PubMed 13. Mueller CA, Peters I, Podlogar M, et al. Vertebral artery injuries following cervical spine trauma: a prospective observational study. Eur Spine J 2011;20: 2202–2209 PubMed 14. Inamasu J, Guiot BH. Vertebral artery injury after blunt cervical trauma: an update. Surg Neurol 2006; 65:238–245, discussion 245–246 PubMed 15. Willis BK, Greiner F, Orrison WW, Benzel EC. The incidence of vertebral artery injury after midcervical spine fracture or subluxation. Neurosurgery 1994; 34:435–441, discussion 441–442 PubMed 16. Veras LM, Pedraza-Gutiérrez S, Castellanos J, Capellades J, Casamitjana J, Rovira-Cañellas A. Vertebral artery occlusion after acute cervical spine trauma. Spine 2000;25:1171–1177 PubMed 17. Spector LR, Kim DH, Affonso J, Albert TJ, Hilibrand AS, Vaccaro AR. Use of computed tomography to predict failure of nonoperative treatment of unilateral facet fractures of the cervical spine. Spine 2006; 31:2827–2835 PubMed

11 Cervical Dislocations (AO Type-C Injuries) William Muñoz, Michael J. Vives, and Saad B. Chaudhary

■■ Introduction Cervical facet dislocations are part of a spectrum of injuries that include ligamentous injury, facet subluxation and dislocation, and fracture. These subaxial cervical spine injuries are most frequently seen in young men who suffered a high-energy trauma, such as a motor vehicle accident, a fall from a height, or a sports injury. However, this injury can also occur in the elderly after a low-energy trauma, especially in those with preexisting degenerative pathology, spinal stenosis, and osteoporosis. Cervical facet dislocations are serious injuries that must be diagnosed quickly and treated urgently. The goals of treatment for cervical facet dislocations are protecting the spinal cord, decompressing the neurologic elements, and restoring mechanical stability to the spinal column. The definitive treatment of these injuries typically involves surgical management by an anterior, posterior, or combined approach, depending on the type of injury, the neurologic status, and the patient’s medical comorbidities and concomitant injuries.

■■ Classification The most widely utilized classification system of cervical fractures and dislocations was orig-

inally described in 1982 by Allen et al.1 This classification system incorporates the mechanism of injury as well as the position of the spine at the time of injury, both inferred by static postinjury radiographs. Facet dislocations are classified as distractive flexion injuries and subclassified as follows: stage I, facet subluxation; stage II, unilateral facet dislocation (Fig. 11.1); stage III, bilateral facet dislocations with 50% displacement (Fig. 11.2); stage IV, complete dislocation. Despite the widespread use of this classification system, it has been recognized that similar injury patterns could be produced by differing mechanisms. The Subaxial Cervical Spine Injury Classification (SLIC) was described more recently by Vaccaro et al.2 This system focuses on three major injury characteristics that are critical to clinical decision making: injury morphology, the integrity of the diskoligamentous complex, and the patient’s neurologic status. A severity scale is applied within each category (Table 11.1), with the sum of the three scores being the composite score. SLIC scores below 4 usually can be managed conservatively. A score ≥ 5 indicates surgical management, whereas a score of 4 can be treated either conservatively or surgically. The AO (Arbeitsgemeinschaft für Osteosynthesefragen) Spine Foundation has recently proposed a new classification system for cervical injuries. Primary injury types are categorized



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a

b

c

d

Fig. 11.1a–d  (a) Lateral radiograph of a patient in traction for a unilateral facet dislocation. Note the 25% translation of C5 on C6. (b) Sagittal magnetic resonance imaging (MRI) of the same patient after an unsuccessful attempt at closed reduction. Note

the extruded disk material posterior to the C5 vertebral body. (c) Lateral intraoperative fluoroscopy during open reduction after diskectomy. (d) Lateral fluoroscopy after structural bone grafting and anterior plating.



Cervical Dislocations (AO Type-C Injuries)

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b

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d

Fig. 11.2a–d  (a) Lateral radiograph of an elderly woman with bilateral facet dislocation after a fall. (b) Because the patient was neurologically intact, MRI was performed. It showed stripping of the

posterior longitudinal ligament but no associated disk herniation. (c) Lateral radiograph after awake closed reduction. (d) Postoperative lateral radiograph after posterior C5–C6 fusion.



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Chapter 11 Table 11.1  Subaxial Cervical Spine Injury Classification (SLIC) and Severity Scale Category

Subcategory

Morphology

No abnormality Compression Burst Distraction (e.g., facet patch, hyperextension) Rotation/translation (e.g., facet dislocation, unstable teardrop, or advanced-stage flexion compression injury) Intact

0 1 2 3 4

Indeterminate (e.g., isolated interspinous widening, MRI signal change only) Disrupted (e.g., widening of disk space, facet patch, or dislocation) Intact Root injury Complete cord injury Incomplete cord injury Continuous cord compression in setting of neurologic deficit ­(neurologic modifier)

1

Diskoligamentous complex (DLC)

Neurologic status

Points

0

2 0 1 2 3 +1

Source: Adapted from Vaccaro AR, Hulbert RJ, Patel AA, et al. The subaxial cervical spine injury classification system. A novel approach to recognize the importance of morphology, neurology, and integrity of the disco-ligamentous complex. Spine 2007;32:2365–2374.

as compression (type A), distraction (type B), and translation (type C). Dislocations are therefore classified as C type injuries, because dislocation of the facet typically results in translation of one vertebral body relative to another (Table 11.2). Facet injuries are also indicated after the primary injury is stated by appending an “F” to level 1 to 4 in parentheses. Facet subluxation, perching, or dislocations are F4. A “BL” modifier indicates bilateral injury. For example, a C6–7 bilateral facet dislocation resulting in anterolisthesis of C6 on 7 would be classified as C6–7:C (F4 BL) If there are different facet injuries at the same level, the right is described first, and then the left. For example, a C6-C7 translational injury (type C) with right-sided facet dislocation (F4) and a left-sided displaced facet fracture (F2) would be classified as C6-C7:C (F4, F2)

■■ Clinical Presentation Facet joint injuries are usually caused by high-­ energy trauma, such as a motor vehicle accident, a fall from a height, or a sports injury. Patients often complain of axial neck pain, and may have paresthesia, palsy, or weakness at the level of the exiting nerve root.3 Patients may also have incomplete or complete spinal cord injury.4

■■ Imaging Patients with suspected cervical spine trauma were traditionally evaluated with radiographs, which include anteroposterior (AP), lateral, and open-mouth odontoid views.5 The entire cervical spine from occiput to the top of T1 should be visualized and evaluated for injury. Computed tomography (CT) increasingly is accepted as the first-line imaging for patients with cervical spine injury, due to its widespread



Cervical Dislocations (AO Type-C Injuries)

Table 11.2  AO Cervical Spine Classification System Primary Injury Compression injuries

Type

Subtype

Description

A0 A1 A2 A3 A4

Distraction injuries

Translational injuries

B1 B2

Posterior tension band injury (bony) Posterior tension band injury (bony capsuloligamentous, ligamentous)

B3

Anterior tension band injury

C

No bony injury or minor injury such as an isolated lamina fracture or spinous process fracture Compression fracture involving a single end plate without involvement of the posterior wall of the vertebral body Coronal split or pincer fracture involving both end plates without involvement of the posterior wall of the vertebral body Burst fracture involving a single end plate with involvement of the posterior vertebral wall Burst fracture or sagittal split involving both end plates Physical separation through fractured bony structures only Complete disruption of the posterior capsuloligamentous or bony capsuloligamentous structures together with a vertebral body, disk, and/or facet injury Physical disruption or separation of the anterior structures (bone/disk) with tethering of the posterior elements Translational injury in any axis displacement or translation of one vertebral body relative to another in any direction

Subgroup Facet injuries

F1 F2 F3 F4 BL

Nondisplaced facet fracture with fragment < 1 cm in height, < 40% of lateral mass Facet fracture with fragment > 1 cm, > 40% lateral mass, or displaced Floating lateral mass Pathologic subluxation or perched/dislocated facet Bilateral injury

availability and increased ability over conventional radiographs to identify injury of the cervical spine.6 CT provides excellent osseous detail of the cervical spine, especially if the ­patient is obese or when evaluating the lower cervical spine where radiographs can be suboptimal. Axial images facilitate detection of associated fractures of the lamina, lateral mass, or pedicles.7 Reformatted images in the sagittal and coronal planes enable evaluation of the relative position of the facet joints and differentiate subluxation from dislocated facets. Magnetic resonance imaging (MRI) provides optimal

evaluation of the soft tissues, including the spinal cord and nerve roots, intervertebral disks, and posterior ligaments. MRI also can be used to assess the extent of spinal stenosis.8 The timing of obtaining MRI is discussed below (see Treatment).

■■ Injury Pathomechanics The facet joints are the only true synovial joints in the cervical spine. The facet capsules are

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Chapter 11 Fig. 11.3  Axial computed tomography (CT) showing dislocated right-sided facet joint with “reverse hamburger bun” appearance.

significant stabilizers of the individual motion segments. Translational injuries are typically the end result of forces that cause disruption of the facet complex and intervertebral disk. The spectrum of facet dislocations includes subluxations, perched facets, unilateral and bilateral dislocations, and fracture dislocations. Facet dislocation, with associated translation of the cephalad vertebra with respect to the caudad vertebra, is considered the most severe form of flexion distraction injury. Failure of the posterior ligamentous complex (PLC) and intervertebral disk are seen in the overwhelmingly majority of cases.9 The injury forces of distraction and translation of the inferior facet result in its coming to rest anterior to the superior facets of the lower level. This has the appearance of a “reverse hamburger bun” on axial CT (Fig. 11.3). When there is no associated fracture of the articular pillar, the facets are locked in the dislocated position. Unilateral injuries often result in 25% translation (spondylolisthesis). The apparent translation of the vertebral body is actually due to rotational displacement. Small fractures of either the superior or inferior facet may be present.10 Bilateral facet dislocations have less rotational deformity but more translation (50%). Patients with normal canal diameters still experience 35% canal narrowing, whereas those with stenotic canals may experience up to 88% canal occlusion.11

■■ Treatment Initial Management Patients should be medically stabilized according to the Advanced Trauma Life Support (ATLS) protocol. Once the patient is hemodynamically stable, the spinal injury can be assessed and treated. Patients should be placed on spinal precautions without excessive manipulation. Neurologic evaluation should be performed and documented initially, and continuously monitored throughout the course of treatment. The patient is assessed as neurologically intact, complete spinal cord injury, or incomplete spinal cord injury, with or without a nerve root injury. Initial management goals include prevention of further spinal cord damage and minimizing secondary injury due to prolonged compression. Traction has generally been recognized as a safe technique for closed reduction in awake and cooperative patients.12 The use of MRI to screen for extruded disk material prior to closed reduction has been recommended by some authors.13 This recommendation stems from a report in which a patient sustained a spinal cord injury from a disk herniation that was presumed to displace into the canal during prone, open operative reduction. To our knowledge, however, no cases of permanent neuro-

logic deficit have been reported in awake and alert patients who have undergone closed reduction. Furthermore, the interpretation of herniated disks by MRI in the context of facet dislocations is somewhat subjective. A survey of members of the Spine Trauma Study Group by Grauer et al14 found poor agreement (kappa values 0.068–0.159) on whether to proceed with closed or open reduction after reviewing the MRI in various clinical scenarios. After ­reviewing the MRI, orthopedic surgeons were significantly more likely than neurosurgeons to choose a closed versus open reduction. Darsaut et al12 reported a prospective series of 17 patients with cervical fracture dislocations treated with closed reduction under serial MRI guidance. Pretraction disk disruption was found in 88% of patients, with posterior herniation in 23% of cases. Traction caused a return of herniated disk material toward the disk space in all cases. As distracting force was increased, sequential MRIs showed that canal dimensions did not diminish at any time in any patient. The authors concluded that closed reduction of subaxial cervical fracture dislocations is a safe and efficient method to decompress the spinal cord that does not result in worsening of herniated disk material or decrease the dimension of the spinal canal. Given the above findings, many authors recommend early closed reduction of facet dislocations, without delay for MRI, in awake and cooperative patients with spinal cord injuries to reduce tension on the cord as quickly as possible.15 When traction reduction is unsuccessful or not preferred due to an uncooperative or unconscious patient, MRI should be performed to investigate the presence of disk herniation prior to open reduction.

■■ Surgical Management Historical Perspective Because facet dislocations primarily affect the posterior bony and ligamentous structures, they have traditionally been stabilized using a posterior approach with posterior wiring, plate and screw, hook plate, and recently rod and screw

Cervical Dislocations (AO Type-C Injuries) segmental fixation.16 Concerns about associated disk herniation13 and improved anterior plate designs have led to an interest in treating these injuries via an anterior approach. Natural anatomic planes used during the anterior approach permit less extensive muscle stripping, potentially leading to reduced infection rates and less postoperative pain.17 Significant controversy exists regarding optimal surgical treatment for these injuries, with biomechanical and clinical data being discrepant (Table 11.3).

Biomechanical Studies Numerous biomechanical studies have shown that posterior stabilization provides increased stability when compared with anterior fixation. Coe et al18 used a human cadaver biomechanical model to evaluate various stabilization techniques. A distractive flexion injury was simulated by disrupting the supraspinous ligament, interspinous ligament, ligamentum flavum, posterior longitudinal ligament, facet joint capsules, and disruption of the intervertebral disk to enable bilateral facet dislocation. Multiple constructs were tested biomechanically, including posterior wiring, lateral mass plates, posterior hook plates, and anterior nonlocked plates. Flexural stiffness and torsional stiffness were not significantly different for all constructs; however, there was a significant increase in the posterior strain during flexion and axial loading, with anterior plates compared with posterior constructs. The authors concluded that anterior nonlocked plates are an inferior method of treating distractive flexion injuries of the cervical spine when compared with posterior fixation techniques. Duggal and colleagues19 studied various fixation techniques for unilateral facet dislocations. Reproducible unilateral facet dislocations were created and then reduced in a human ­cadaver model. During all modes of loading, posterior lateral mass plates performed significantly better than anterior cervical diskectomy and fusion (ACDF) with an anterior nonlocking plate in the multiple motion parameters. The authors concluded that lateral mass fixation provides better immobilization than ACDF with anterior nonlocking plate for these injuries.

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Chapter 11 Table 11.3  Biomechanical and Clinical Studies Study Type

Authors

Experimental Design

Conclusion

Biomechanical

Coe et al18

Cadaver; posterior ligaments, PLL and disk sectioned to create bilateral dislocation; tested posterior wiring, lateral mass plates, and anterior nonlocked plate Cadaver; unilateral dislocation, then reduced Cadaver: tested intact, then after complete diskectomy/ PLL section, then ACDF with locked plate, then complete posterior release (simulated bilateral dislocation) Retrospective, 14 pts; CFS 4-5 or DFS 2–3; Caspar plate and structural bone graft Retrospective, 22 pts; bilateral dislocations–closed reduced; anterior structural graft, with locked unicortical plate Prospective, randomized; 52 pts with unstable cervical injuries and SCI; closed reduced; patterns amenable to either anterior or posterior approach Retrospective, 41 consecutive pts; traumatic dislocations; all treated with anterior approach

Flexural and torsional stiffness similar for all constructs; increased posterior strain with anterior plate compared with posterior methods

Duggal et al19 Paxinos et al20

Clinical

Garvey et al23 Razack et al24

Brodke et al25

Reindl et al22

Song et al26

Johnson et al27

Retrospective, 50 pts with unilateral or bilateral dislocations; 38 treated anterior alone; 12 combined anterior-posterior Retrospective, 87 pts; unilateral or bilateral dislocation or fracture-dislocation; all treated with anterior structural graft/plate

Posterior lateral mass plating > ACDF with nonlocking plate With preload (follower load), ACDF with locked plate effectively stabilized simulated DFS3 injury Avg f/u 30 months; no loss of fixation; all solid fusion by X-ray Avg f/u 32 months; all pts rated as solid fusion; one instrumentation failure No clinical difference in outcomes based on approach; 100% fusion in posterior group, 90% in anterior group (not significant) Anterior approach successful most cases; 25% irreducible by anterior approach and necessitated posterior procedure No significant difference in fusion rate/time, complication rate or clinical results; 3 instrumentation failures in anterior alone group Loss of postoperative alignment in 13%; no correlation unilateral vs bilateral; failure correlated with end-plate and facet fractures

Abbreviations: ACDF, anterior cervical diskectomy and fusion; Avg f/u, average follow-up; CFS, compressive flexion stage; DFS, distractive flexion stage; PLL, posterior longitudinal ligament; pts, patients; SCI, spinal cord injury.

Although many biomechanical studies support posterior constructs as being superior to anterior procedures, other studies suggest that physiological preload has an important stabilizing affect in the cervical spine that is not al-

ways accounted for in biomechanical studies.20 Physiological preload from muscle activation is thought to be an important stabilizing mechanism after distraction-flexion injuries.21 Results of biomechanical studies that account for pre-

load show comparable stabilization of anterior and posterior procedures, which is consistent with clinical experience.20

Clinical Studies Despite biomechanical studies supporting posterior constructs, the anterior approach has become increasingly popular, as it enables the surgeon to decompress the spinal canal directly, and entails low morbidity and ease of patient positioning.22 Clinical studies are generally small series, but they have shown acceptable clinical results in most cases of cervical dislocation treated by anterior fusion with locked plates. A retrospective study of 14 patients who sustained acute cervical spine fractures or dislocations with associated posterior ligamentous disruption (DFS2 or DFS3) that were treated with anterior decompression, structural bone graft, and anterior nonlocked plating was conducted by Garvey et al.23 At an average of 30 months’ follow-up, they saw no loss of fixation, and solid arthrodesis as evaluated by X-ray in all patients. Another retrospective study of 22 patients treated with anterior structural graft and locked unicortical plating for bilateral facet fracture dislocations found one instrumentation-related failure, but all patients ultimately had solid fusion on the final follow-up examination.24 Brodke et al25 performed a prospective randomized study of 52 patients with unstable cervical injuries, with associated spinal cord injury, that were able to be closed reduced preoperatively. All patients required surgical stabilization, with injury patterns that were amenable to either an anterior or posterior stabilization procedure. The posterior stabilization group demonstrated a 100% fusion rate, compared with a 90% fusion in the anterior stabilization group, with the difference not being statistically significant. The authors concluded that there were no significant differences in fusion rates, alignment, neurologic recovery, or long-term complaints of pain in patients treated with either anterior or posterior fusion and instrumentation. Another retrospective review of 50 patients treated with

Cervical Dislocations (AO Type-C Injuries) either anterior plating and fusion (38 patients) or circumferential fusion (12 patients) found no significant differences in fusion rates, complication rates, and neurologic recovery between the treatment groups.26 Johnson et al27 reviewed the radiographs of 87 patients with unilateral or bilateral facet dislocations and fractures treated with anterior structural graft and plating to evaluate factors that predispose to loss of alignment. They found that loss of postoperative alignment occurred in 13% of the facet dislocations and fractures treated with anterior cervical diskectomy, fusion, and plating. Radiographic failure was strongly correlated with the presence of endplate fracture and less strongly with facet fracture on injury radiographs. Pseudarthrosis was correlated with the presence of end-plate fracture. They did not find an increased failure rate when comparing unilateral to bilateral facet dislocations. The authors concluded that the presence of an end-plate fracture or facet fracture in association with a unilateral or bilateral facet fracture dislocation or subluxation should alert the surgeon to a high risk of radiographic failure with anterior plating alone, and that a primary posterior fusion or a combined anterior/ posterior approach should be considered.

Factors Contributing to Treatment Decision Despite the biomechanical and clinical data presented above, no consensus exists regarding the preferred surgical approach to facet dislocations. A survey analysis of 25 members of the Spine Trauma Study Group illustrates the variations in surgical treatment for cervical facet dislocations.28 Members evaluated 10 facet dislocation cases and were asked to indicate their preferred surgical approach. Poor agreement was observed among surgeons in the choice of surgical approach (kappa < 0.1). There was a trend toward an anterior or combined approach when a disk herniation was present. The authors believe that the poor agreement on the treatment of these injuries likely reflects a combination of factors including surgeon training and experience. They also suggest that the treat-

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Chapter 11 ment decisions are likely to be affected by the neurologic status of the patient, interpretation of a disk herniation, and the classification of the injury as a unilateral or bilateral injury. With few objective criteria on which to base a treatment decision and almost no treatment guidelines, there are multiple factors to consider when choosing a treatment approach. Factors include surgeon experience and comfort with open reduction techniques, interpretation of MRI findings, and associated end-plate and facet fractures. The habitus of a patient as well as the injury level also may affect treatment decisions, as proper intraoperative images and postoperative wound infections are concerns in these situations.

Fig. 11.4  Suggested treatment algorithm.

Treatment Algorithm The surgical management of cervical facet dislocations is highly variable, with few guidelines to help surgeons make a clinical decision. Given that only level IV data are available to guide treatment, only suggestions can be made. By following the principle of “safety of the spinal cord first,” Nassr et al28 and the Spine Trauma Study Group proposed an algorithm that we have slightly modified to serve as a guide in managing these injuries (Fig. 11.4). This treatment algorithm is based on the result of attempted closed reduction, presence or absence of a traumatic disk herniation, and the injury type (unilateral versus bilateral). The

first branch point when using this algorithm is whether or not successful closed reduction has been achieved before taking the patient to the operating room. Cases in which closed reduction is not attempted, due to the patient being obtunded or to concerns about disk herniation, are treated similarly to those of unsuccessful closed reduction attempts. The other premise in using the suggested algorithm is that an MRI

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is obtained in all patients before they undergo surgery. Associated disk herniation seen on MRI dictates the preferred management after attempted closed reduction. In cases of suspected disk herniation, the use of an anterior or anterior and posterior procedure to decompress the neural elements regardless of the patient’s neurologic status is  recommended (Fig. 11.5). If an anterior

a

b

c

d

Fig. 11.5a–d  (a) Midline MRI demonstrating bilateral facet dislocation with associated disk herniation in a young man with concomitant head injury. (b,c) Parasagittal MRI cuts demonstrating

bilateral dislocated facets. (d) Postoperative lateral radiograph after anterior diskectomy with open reduction and anterior-posterior fusion.



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Chapter 11 procedure is chosen as the initial approach in the presence of an unreduced dislocation that is due to disk herniation, then an open anterior reduction may be attempted. If an anterior open reduction is successful, it can be followed by an anterior fusion and instrumentation. If an attempted anterior open reduction is unsuccessful, then a subsequent posterior open reduction and stabilization is required. The presence of bilateral facet dislocation often signifies a higher energy injury, and some authors favor the addition of posterior fixation due to the loss of reduction occasionally seen with anterior-only procedures.28 In cases of unsuccessful closed reduction for bilateral facet dislocation with no disk herniation, a stand-alone posterior procedure is a reasonable option. In this situation, many surgeons would reinforce an anterior procedure with additional posterior fixation, so a standalone posterior procedure entails less surgery for the patient. This scenario in the setting of complete spinal cord injury had the highest tendency for a posterior approach in the Spine Trauma Study Group survey.28 In our opinion, if reduction is to be done posteriorly, there should be no question as to whether there is any “at risk” disk material that could potentially lead to cord compression and neurologic deterioration. Open posterior reduction is done with the patient in the prone position, making it difficult to obtain controlled distraction and, therefore, more likely to drag disk material into the canal. Anterior open reduction has been shown to  be an effective surgical option for patients who fail closed reduction.22 Following complete diskectomy, gradual distraction with Gardner-­ Wells tongs or Casper retractor pins is attempted. If further distraction is needed, a laminar spreader in the affected disk space is used to disengage the facets. Reduction is successfully achieved in the majority of dislocations with cephalad rotation to translate the anteriorly dislocated cephalad vertebral body posteriorly under fluoroscopic guidance. Anterior open reduction and stabilization monitored by spinal cord evoked potentials has been shown to be an effective and safe method for

treatment in patients without or with a mild spinal cord injury.29 Unilateral dislocations may require open rotational manipulation similar to closed reduction techniques to successfully attain reduction. Failure to achieve anterior open reduction has been reported in up to 25% of attempted cases.22 A surgical technique successfully used in the treatment of patients with fracture dislocations that are irreducible through an anterior open approach was described by Allred and Sledge.30 After diskectomy and end-plate preparation, a tricortical bone graft was harvested from the iliac crest, placed in the interspace, and held with a buttress plate screwed in two places into the superior vertebral body. The anterior wound then was closed, and the posterior elements were exposed and the facets reduced by flexing the neck and posteriorly translating the superior segment. Fluoroscopy was used during the reduction to ensure that the graft was pulled into the interspace, that the screws in the buttress plate did not pull out of the superior vertebral body, and that the reduced graft did not impinge on the spinal cord. Posterior fusion was performed and the posterior wound closed. This technique eliminates the need for a third procedure to complete anterior stabilization after posterior reduction and fusion for a failed anterior reduction.

Vertebral Artery Injury Vertebral artery injury (VAI) may present as a spectrum of injury from remaining clinically silent to posterior circulation stroke, quadriplegia, and death. Between 70% and 78% of VAIs occur in association with a cervical spine injury, and VAI has been reported to be present in 19 to 39% of cervical spine fractures.31 The relatively high reported incidence of VAI and the wide array of possible clinical sequelae make early identification of these high-risk patients essential. A VAI can occur as an intimal tear, a dis­ section, a pseudoaneurysm, an occlusion, or a transection. Intimal tears entail the torn intima occasionally swinging into and occluding the vessel lumen. Arterial dissection entails the

possibility that blood might collect in the arterial wall and create a false lumen that can obstruct the arterial lumen, resulting in thrombus formation. A pseudoaneurysm may form outside of the arterial walls, and, if large enough, can impinge and obstruct the artery. Transection is the most severe form of VAI and can lead to death. Patients who are at high risk for a VAI should be screened at initial presentation, including patients with basilar skull fractures, occipitocervical dissociations, fracture displacement into the transverse foramen of more than 1 mm, ankylosing spondylitis/diffuse idiopathic skeletal hyperostosis, and cervical facet subluxation/ dislocations.32 Angiography was traditionally considered the “gold standard” for diagnosis of VAI. Recent studies have demonstrated the less invasive multidetector computed tomography angiogram (MDCTA) to be an effective screening tool with detection rates similar to those of angiography,33 making it the primary method for diagnosis at many trauma centers. Treatment of symptomatic VAI includes anticoagulation, blood pressure control, thrombolytic therapy, and endovascular or surgical procedures. There is no consensus in the literature, however, regarding the benefit of anticoagulation versus antiplatelet therapy for asymptomatic cervical arterial dissection.32,34 Low-dose systemic heparin therapy with a partial thromboplastin time goal of 40 to 50 seconds was recommended by Biffl et al.35 This is followed by oral anticoagulation therapy for 3 to 6 months or until angiography results have returned to normal. Patients unable to receive heparin are treated with antiplatelet therapy in its place. Many centers employ oral antiplatelet therapy for 3 months in patients with VAI requiring surgical management of their spinal injuries to decrease the risk of stroke and mitigate the risk of postsurgical bleeding complications.

Cervical Dislocations (AO Type-C Injuries)

■■ Chapter Summary Cervical facet dislocations are part of a broad spectrum of injuries and encompass a variety of injury patterns. These patients must be treated urgently and carefully, with stabilization and protection of the cervical spine. Conventional and advanced imaging techniques provide excellent visualization of the injury and associated neurologic compression. Selection of the appropriate treatment is based on the goals of providing mechanical stability to the spinal column and neurologic decompression. Surgical intervention can be done by an anterior, posterior, or combined approach. This decision is made based on several factors, including the type of injury, the neurologic status, and the patient’s medical comorbidities and concomitant injuries. Pearls ◆◆ Careful history and physical examination, along

with advanced imaging modalities, including CT and MRI, should be used to identify the type and extent of injury. ◆◆ Closed reduction of cervical facet dislocation can be attempted in the awake, alert, and cooperative patient. ◆◆ These injuries can be treated successfully surgically by an anterior, posterior, or combined approach, and should be based on the success of closed reduction in the presence of disk herniation. Pitfalls ◆◆ An MRI should be obtained prior to any surgical

intervention.

◆◆ When an associated herniated disk is present, an

anterior diskectomy and open reduction is favored over open posterior reduction. ◆◆ Vertebral artery injury is associated with cervical facet dislocations, so these patients should be screened and treated appropriately when detected.

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Chapter 11 References

Five Must-Read References 1. Allen BL Jr, Ferguson RL, Lehmann TR, O’Brien RP. A  mechanistic classification of closed, indirect fractures and dislocations of the lower cervical spine. Spine 1982;7:1–27 PubMed  2. Vaccaro AR, Hulbert RJ, Patel AA, et al; Spine Trauma Study Group. The subaxial cervical spine injury classification system: a novel approach to recognize the importance of morphology, neurology, and integrity of the disco-ligamentous complex. Spine 2007;32: 2365–2374 PubMed 3. Jacobs B. Cervical fractures and dislocations (C3-7). Clin Orthop Relat Res 1975;109:18–32 PubMed 4. Bohlman HH. Acute fractures and dislocations of the cervical spine. An analysis of three hundred hospitalized patients and review of the literature. J Bone Joint Surg Am 1979;61:1119–1142 PubMed 5. Harris JH, Edeiken-Monroe B. The Radiology of Acute Cervical Spine Trauma. Baltimore: Williams & Wilkins; 1987 6. Brown CV, Antevil JL, Sise MJ, Sack DI. Spiral computed tomography for the diagnosis of cervical, thoracic, and lumbar spine fractures: its time has come.  J Trauma 2005;58:890–895, discussion 895– 896 PubMed 7. Shanmuganathan K, Mirvis SE, Levine AM. Rotational injury of cervical facets: CT analysis of fracture patterns with implications for management and neurologic outcome. AJR Am J Roentgenol 1994;163: 1165–1169 PubMed 8. Vaccaro AR, Madigan L, Schweitzer ME, Flanders AE, Hilibrand AS, Albert TJ. Magnetic resonance imaging analysis of soft tissue disruption after flexion-distraction injuries of the subaxial cervical spine. Spine 2001;26:1866–1872 PubMed 9. Vaccaro AR, Nachwalter RS. Is magnetic resonance imaging indicated before reduction of a unilateral cervical facet dislocation? Spine 2002;27:117–118 PubMed 10. Holdsworth F. Fractures, dislocations, and fracture-­ dislocations of the spine. J Bone Joint Surg Am 1970; 52:1534–1551 PubMed 11. Ivancic PC, Pearson AM, Tominaga Y, Simpson AK, Yue JJ, Panjabi MM. Mechanism of cervical spinal cord injury during bilateral facet dislocation. Spine 2007; 32:2467–2473 PubMed 12. Darsaut TE, Ashforth R, Bhargava R, et al. A pilot study of magnetic resonance imaging-guided closed reduction of cervical spine fractures. Spine 2006;31: 2085–2090 PubMed 13. Eismont FJ, Arena MJ, Green BA. Extrusion of an ­intervertebral disc associated with traumatic subluxation or dislocation of cervical facets. Case report. J Bone Joint Surg Am 1991;73:1555–1560 PubMed 14. Grauer JN, Vaccaro AR, Lee JY, et al. The timing and influence of MRI on the management of patients

with cervical facet dislocations remains highly variable: a survey of members of the Spine Trauma Study Group. J Spinal Disord Tech 2009;22:96–99 PubMed 15. Wing P, Dalsey W, Alvarez E. Early acute management in adults with spinal cord injury: a clinical practice guideline for healthcare professionals. Consortium for spinal cord medicine guideline. 2008;31: 408–479 16. Graham AW, Swank ML, Kinard RE, Lowery GL, Dials BE. Posterior cervical arthrodesis and stabilization with a lateral mass plate. Clinical and computed tomographic evaluation of lateral mass screw placement and associated complications. Spine 1996;21: 323–328, discussion 329 PubMed 17. Kwon BK, Fisher CG, Boyd MC, et al. A prospective randomized controlled trial of anterior compared with posterior stabilization for unilateral facet injuries of the cervical spine. J Neurosurg Spine 2007;7: 1–12 PubMed 18. Coe JD, Warden KE, Sutterlin CE III, McAfee PC. Biomechanical evaluation of cervical spinal stabilization methods in a human cadaveric model. Spine 1989; 14:1122–1131 PubMed 19. Duggal N, Chamberlain RH, Park SC, Sonntag VK, Dickman CA, Crawford NR. Unilateral cervical facet dislocation: biomechanics of fixation. Spine 2005;30: E164–E168 PubMed 20. Paxinos O, Ghanayem AJ, Zindrick MR, et al. Anterior cervical discectomy and fusion with a locked plate and wedged graft effectively stabilizes flexion-­ distraction stage-3 injury in the lower cervical spine: a biomechanical study. Spine 2009;34:E9–E15 PubMed 21. Henriques T, Olerud C, Bergman A, Jónsson H Jr. Distractive flexion injuries of the subaxial cervical spine treated with anterior plate alone. J Spinal Disord Tech 2004;17:1–7 PubMed 22. Reindl R, Ouellet J, Harvey EJ, Berry G, Arlet V. Anterior reduction for cervical spine dislocation. Spine 2006;31:648–652 PubMed 23. Garvey TA, Eismont FJ, Roberti LJ. Anterior decompression, structural bone grafting, and Caspar plate stabilization for unstable cervical spine fractures and/or dislocations. Spine 1992;17(10, Suppl):S431– S435 PubMed 24. Razack N, Green BA, Levi AD. The management of traumatic cervical bilateral facet fracture-dislocations with unicortical anterior plates. J Spinal Disord 2000;13:374–381 PubMed 25. Brodke DS, Anderson PA, Newell DW, Grady MS, Chapman JR. Comparison of anterior and posterior approaches in cervical spinal cord injuries. J Spinal Disord Tech 2003;16:229–235 PubMed 26. Song KJ, Lee KB, Kim SR. Availability of anterior cervical plating according to the severity of injury in

distractive flexion injury in lower cervical spine. J Korean Orthop Assoc 2005;40:195–202 27. Johnson MG, Fisher CG, Boyd M, Pitzen T, Oxland TR, Dvorak MF. The radiographic failure of single segment anterior cervical plate fixation in traumatic cervical flexion distraction injuries. Spine 2004;29: 2815–2820 PubMed 28. Nassr A, Lee JY, Dvorak MF, et al. Variations in surgical treatment of cervical facet dislocations. Spine 2008;33:E188–E193 PubMed 29. Du W, Wang C, Tan J, Shen B, Ni S, Zheng Y. Management of subaxial cervical facet dislocation through anterior approach monitored by spinal cord evoked potential. Spine 2014;39:48–52 PubMed 30. Allred CD, Sledge JBC. Irreducible dislocations of the cervical spine with a prolapsed disc: preliminary ­results from a treatment technique. Spine 2001;26: 1927–1930, discussion 1931 PubMed 31. Biffl WL, Ray CE Jr, Moore EE, et al. Treatment-related outcomes from blunt cerebrovascular injuries: im-

Cervical Dislocations (AO Type-C Injuries) portance of routine follow-up arteriography. Ann Surg 2002;235:699–706, discussion 706–707 PubMed 32. Lebl DR, Bono CM, Velmahos G, Metkar U, Nguyen J, Harris MB. Vertebral artery injury associated with blunt cervical spine trauma: a multivariate regression analysis. Spine 2013;38:1352–1361 PubMed 33. Paulus EM, Fabian TC, Savage SA, et al. Blunt cerebrovascular injury screening with 64-channel multidetector computed tomography: more slices finally cut it. J Trauma Acute Care Surg 2014;76:279–283, discussion 284–285 PubMed 34. Kennedy F, Lanfranconi S, Hicks C, et al; CADISS Investigators. Antiplatelets vs anticoagulation for dissection: CADISS nonrandomized arm and meta-analysis. Neurology 2012;79:686–689 PubMed 35. Biffl WL, Moore EE, Elliott JP, et al. The devastating potential of blunt vertebral arterial injuries. Ann Surg 2000;231:672–681 PubMed

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12 Cervicothoracic Junction Injuries Ripul Rajen Panchal

■■ Introduction Injuries to the cervicothoracic junction (CTJ) are rare. Although the reported incidence of CTJ injury ranges from 2 to 9% of all cervical spinal traumas,1–3 the true incidence is difficult to determine due to failures to diagnose a CTJ injury on initial evaluation. In patients who are diagnosed, the prevalence of neurologic impairment is high (59–83%).1,2,4 The most common causes of CTJ injuries are motor vehicle accidents and falls from a height that result in fracture-dislocation (Fig. 12.1).1,5 Physicians should maintain a high level of suspicion on initial assessment in patients who are involved in high-energy trauma. Early identification of CTJ injury is key to determining the appropriate management and enabling an optimal prognosis.1,3

■■ Clinical Anatomy The CTJ is a unique region of the spinal column, consisting of the C7 and T1 vertebrae and the intervertebral disk (Fig. 12.2). However, due to the anatomic and biomechanical variability of this region, issues concerning the CTJ often include the C7 thorough T3 vertebrae.6 The CTJ is a transition zone, from a flexible lordotic cervical spine to a rigid kyphotic thoracic spine. This change in spinal curvature and stiffness

renders the CTJ a region of high stress that is predisposed to instability when subjected to trauma. The CTJ is also a transition zone in terms of bony morphology.7 The lateral mass of the cervical spine tends to decrease in size and transitions into the wide pedicles of the upper thoracic spine; these changes create a challenge in terms of instrumentation and stabilization. Biomechanically, the CTJ is an area subject to significant external forces creating a large lever arm with fixed a thoracic spine and a hypermobile cervical spine, in comparison with the thoracic spine. Especially in those patients who have undergone previous vertebral fusion procedures, this region is susceptible to failure post-instrumentation, even with minor trauma (Fig. 12.3a,b).

■■ Diagnosis History and Physical Examination Despite the low incidence of CTJ injuries, the occurrence of neurologic impairment associated with CTJ injury is high and the impairment is usually severe. Nichols and colleagues1 identified 37 patients with CTJ injury in their retrospective review of 397 patients with cervical spinal injuries. They reported that 22 of the 37 patients (59%) had neurologic impair-



Fig. 12.1  Midline sagittal computed tomography (CT) reconstruction demonstrating traumatic fracture-dislocation of the cervicothoracic junction (CTJ) at C7-T1.

Cervicothoracic Junction Injuries ment, and 12 of the 22 impaired patients (55%) were tetraplegic or paraplegic. Chen and Eismont7 reported that 15 of 18 patients (83%) had neurologic deficits and 10 of the 15 impaired patients (67%) had complete spinal cord injury. The high occurrence of significant impairment is the result of the large spinal cord–to-canal ratio; the spinal cord is thus susceptible to severe compromise with dislocation-type injuries. Additionally, the blood supply to the spinal cord in this region is limited.4 The most common presenting complaint of patients with CTJ injury is pain.8 Due to the mechanisms involved in CTJ injuries, most patients present with a global injury of this ­region, and isolated radiculopathy is uncommon.9 Clinicians should dorsally palpate the CTJ area for point tenderness or step-offs.7 On exam, patients are likely to exhibit signs of myelopathy: upper motor neuron signs, weakness, pathological reflexes (Babinski’s sign), and bowel or bladder dysfunction. However, in the setting of concomitant injury involving other regions of the central nervous system (CNS), or

Fig. 12.2  Schematic of the cervicothoracic junction. (Illustration by Avani R. Panchal.)

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a

b

c

Fig. 12.3a–d  Lateral radiograph (a) and lateral CT reconstruction (b) illustrating kyphotic deformity resulting from CTJ instrumentation failure with T3 fracture (arrow). Intraoperative image (c) and lateral

d

postoperative radiograph (d) showing dorsal-only approach to correct the CTJ deformity, with T1 pedicle subtraction osteotomy due to restricted access ventrally.

under the influence of drugs or medications, these features may be difficult to identify. In Nichols et al’s1 series, nine patients (24%) had no pain or neurologic deficits and seven of them (19%) had an altered level of consciousness from a traumatic brain injury or substance abuse. Therefore, when evaluating a traumatized patient, it is crucial to carry out adequate imaging studies.

Diagnostic Studies The CTJ is a difficult region to visualize on the supine lateral radiographs that are usually done in the emergency room. A swimmer’s view may provide adequate visualization of the CTJ alignment on plain films, but such views may be difficult to obtain in obese patients or in those with a short neck or large shoulders. In Evans2 series, nearly two thirds of the patients were misdiagnosed on admission, and one patient was diagnosed only when he became paraplegic after mobilization. Kaneriya and coworkers10 found that the routine three-view films failed to demonstrate CTJ in 50 of 196 trauma patients (26%). The risk of noncontiguous injury in patients with CTJ injury is estimated to be up to 15%. When injury in the CTJ region is suspected, computed tomography (CT) or magnetic resonance imaging (MRI) should be considered, especially when the patient has experienced high-energy trauma and the clinical examination or radiographs are limited by a concomitant injury, substance abuse, or patient habitus. High-resolution, multidetector CT has become the imaging modality of choice at large level I trauma centers due to its speed, sensitivity, and accuracy in diagnosing fractures, and it may be particularly useful in detecting CTJ injury. Reconstructed CT imaging tends to illustrate the subtle posterior bony injuries that are overlooked on radiographs.7 MRI facilitates determining the presence of soft tissue injury, including disk herniation, ligamentous injury, and neural injury. The utility of MRI prior to closed reduction in an awake and alert patient is uncertain.11 CT angiography or magnetic resonance angiography may help determine local vascular disruption.

Cervicothoracic Junction Injuries

■■ Management The injuries to the CTJ region include ligamentous injury, disk rupture, fractures (body, arch, and facets), and dislocations. Vaccaro et al12 describe the Subaxial Cervical Spine Injury Classification (SLIC) scale, which assesses the morphology, the diskoligamentous complex, and the neurologic status. A weighted score from the three categories determines the severity of injury and helps guide management (≤ 3 = nonoperative, 4 = “gray zone,” and ≥ 5 = surgical). The AO (Arbeitsgemeinschaft für Osteosynthesefragen) classification system for subaxial spine fractures is based on the thoracic and lumbar classification originally described by Magerl’s group.13,14 It also categorizes the injuries into three types based on injury morphology: type A, compression injury; type B, distraction injuries; and type C, torsion injuries. However, there is no classification system specific to CTJ injury. Fig. 12.4 provides an algorithm that may assist with the management of patients with CTJ injury. Stable injuries are managed with bracing, but they should be followed for delayed instability, especially in those patients with purely ligamentous injury. CTJ injuries with subluxation or dislocation require immediate reduction for neural decompression.

Nonsurgical An external orthosis or halo immobilization should be considered for injuries involving spinous process fractures, lateral mass fractures, compression fractures without deformity, and subluxations that are deemed stable injuries. An orthosis with chest extension or halo vest may provide adequate stabilization. However, kyphosis greater than 11 degrees or subluxation greater than 3.5 mm on radiographs (especially upright films) should raise a concern regarding instability.15 CTJ injury involving dislocation must undergo early closed reduction and stabilization. Skull traction with Gardner-­ Wells tongs or halo ring may require a weight up to 140 pounds.4,16 Prompt surgical reduction should be performed if closed reduction fails.

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Chapter 12 nation of both (Table 12.1). The location of the neural compression dictates the approach for decompression.7 Despite advances in techniques and instrumentation technologies, there is no one best approach. The approach of choice depends on the surgeon’s understanding of the clinical and radiographic presen­ tation of the patient (spinal level of injury, direction of neural compression, exposure required, and body habitus), and the surgeon’s familiarity with the potential techniques and instrumentation systems.6 If indicated, intraoperative traction should be employed, starting with 10 pounds and increasing by 5 pounds per spinal level as approaching more distally from the head. Intraoperative neurophysiological monitoring of the spinal cord and nerve root integrity must be utilized. Fig. 12.4  Basic algorithm for management of CTJ injuries.

Surgical Approaches The goals of surgical management of CTJ injuries are neural decompression, realignment of spine, and stabilization of the CTJ. The surgical approaches can be ventral, dorsal, or a combi-

Ventral Approaches Ventral approaches provide restricted exposure of the CTJ. The CTJ is surrounded by osseous (manubrium, sternoclavicular joint, and medial clavicle) and nonosseous (vascular and nonvascular) structures (Fig. 12.2). The vascular structures include the great vessels (left subclavian vein, left brachiocephalic veins, left

Table 12.1  Surgical Approaches to CTJ Injury Low Cervical

Low Cervical with Extension

Posterior

Posterior with Extension

Transverse or longitudinal (medial to sternocleidomastoid muscle) Fig. 12.5 Access to C7-T1

Transmanubrial; transsternal

Midline

Costotransversectomy; lateral extracavitary approach

Fig. 12.6 Access below C7-T1

Advantages

Familiar approach, enables anterior column reconstruction

Disadvantages

Injury to vital structures

Direct visualization of thecal sac, enables anterior column reconstruction Injury to vital structures; high morbidity

Fig. 12.7 Posterior decompression and stabilization Familiar approach

Fig. 12.8 Anterior and posterior stabilization Avoid vital structures; enables anterior column reconstruction High morbidity (pulmonary)

Approach description

Illustration Indication(s)

Unable to reconstruct anterior spinal column



Cervicothoracic Junction Injuries

Fig. 12.5  Low cervical transverse or longitudinal (medial to sternocleidomastoid muscle) approach to CTJ injury. (Illustration by Avani R. Panchal)

Fig. 12.6  Low cervical approach with transmanubrial-­ transsternal extension to a CTJ injury. (Illustration by Avani R. Panchal)

Fig. 12.7  Posterior midline approach to a CTJ injury. (Illustration by Avani R. Panchal)

Fig. 12.8  Posterior approach with extension for a costotransversectomy (short arrow), with a lateral extracavitary approach (long arrow) to a CTJ injury. (Illustration by Avani R. Panchal)

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Chapter 12 common carotid artery, subclavian arteries, and the aortic arch). The nonvascular structures include the trachea, esophagus, recurrent laryngeal nerves (RLNs), and thoracic duct. Additionally, the CTJ transition from lordotic cervical spine to kyphotic thoracic spine places the proximal thoracic vertebrae deep, and with limited ventral access. Many spine surgeons are familiar with the standard Smith-Robinson anteromedial approach or the low anterior cervical approach. An approach from the left side is favored due to the more predictable path of the RLN, but the thoracic duct is at risk of injury with this approach. This technique provides access to C7-T1 in most cases. Patients with short necks, proximal thoracic kyphosis, or high shoulders may require an extension of this approach. During preoperative planning, the surgeon should draw an intervertebral disk line on a sagittal image, parallel to the lowest intervertebral disk space of interest (Fig. 12.9); if the ventral osseous structures (manubrium, first rib, or sternoclavicular joint) fall cephalad to the line, the surgeon should prepare for a likely low anterior cervical approach with an extension (transmanubrial or transsternal) or consider posterior approaches.17 Low cervical approaches with extension usually provide exposure down to T3.18 The incision is extended down the midline over the manubrium and if necessary further down over the sternum in a variable hockey-stick fashion. For transmanubrial extension, the osteotomy should be lateralized to the left side, involving the manubrium and left medial aspect of the clavicle. The manubrium and sternoclavicular joint can be disarticulated as one, with the sternocleidomastoid muscle still attached. The local nonosseous structures should be identified and dissected with caution. The RLN tends to be located between the trachea and the esophagus. Further extension of the osteotomy to include the sternum provides exposure below the CTJ region. The morbidity rates for low cervical extension approaches are high, and so this approach should be reserved for selected patients; an approach surgeon should be consulted when possible. Preoperative imaging must be thor-

Fig. 12.9  Midline sagittal CT reconstruction displaying intervertebral disk line, indicating the need for a ventral extension approach to access this region.

oughly studied to identify relevant anatomy to prevent complications. Additionally, anterior stabilization alone may not be enough to satisfy the biomechanical requirements of the CTJ, and should be supplemented with posterior stabilization; there is a one-third failure rate for the stand-alone anterior approaches.19

Dorsal Approaches A dorsal approach is the mainstay approach for all spine surgeons. Dorsal techniques permit unlimited spinal level of decompression, reduction, and stabilization, whereas ventral approaches, even with extension, provide a restricted exposure to the ventral spine. Posterior decompression via laminectomies should be accompanied by instrumented stabilization to prevent kyphotic deformity at the CTJ.6 The extensions of this approach are the posterior lateral approaches: transpedicular, costotrans-

versectomy, and lateral extracavitary. The transpedicular approach enables lateral decompression (Fig. 12.3c,d). The costotransversectomy involves removal of the transverse process, 2 to 3 cm of the proximal rib, and the pedicle; this removal provides access to the anterolateral spinal cord. The lateral extracavitary approach (which requires much longer rib resection) enables ipsilateral ventral decompression and reconstruction of the anterior column. When done bilaterally, the lateral extracavitary approach provides circumferential access to the thecal sac, but this bilateral approach is technically challenging. Resnick and Benzel20 reported a high incidence of adverse events (55%), with pulmonary events as the most common. The dorsal approach is the approach of choice for most spine surgeons for surgical management of CTJ injuries, because it permits decompression, realignment, and spine stabilization via a single incision.

■■ Chapter Summary The CTJ region is a unique transition zone in which injury is infrequent, but when it does occur it is often associated with severe impairment. CTJ injuries are challenging to diagnose, requiring CT and MRI. Early diagnosis and dislocation reduction may improve the clinical outcome; however, in cases with complete spinal cord injury, the prognosis is poor. Nonoperative management should be considered for stable CTJ injuries; an orthosis should be considered with close follow-up to identify delayed instability. Unstable injuries should be treated surgically, with ventral, dorsal, or com-

Cervicothoracic Junction Injuries bination approaches for neural decompression, realignment of spine, and stabilization of the CTJ. Despite advances in techniques and instrumentation, prevention of complications still depends on the surgeon’s understanding of the pertinent anatomy based on preoperative imaging, and on the surgeon’s experience with the chosen approach. CTJ injuries should be approached with caution due to the complexity of this region and the potential high perils of detrimental complications. Pearls ◆◆ Physicians should maintain a high level of suspi-

cion for CTJ injury when assessing patients involved in high-energy trauma, until such injury is excluded with adequate imaging. ◆◆ Early closed reduction and decompression of the spinal cord may improve prognosis. ◆◆ A surgical approach (ventral, dorsal, or combination of both) should be considered based on the clinical and radiographic presentation, and on the surgeon’s experience with appropriate approaches. Pitfalls ◆◆ Do not settle for poor visualization of the CTJ re-

gion on imaging.

◆◆ Do not operate on neurologically intact patients

without neurophysiological monitoring.

◆◆ Avoid dorsal decompression of the CTJ without

stabilization.

◆◆ Purely ligamentous injuries are unstable and re-

quire stabilization.

Acknowledgement I thank Avani R. Panchal for the chapter illustrations.

References

Five Must-Read References  1. Nichols CG, Young DH, Schiller WR. Evaluation of cervicothoracic junction injury. Ann Emerg Med 1987; 16:640–642 PubMed  2. Evans DK. Dislocations at the cervicothoracic junction. J Bone Joint Surg Br 1983;65:124–127 PubMed 3. Amin A, Saifuddin A. Fractures and dislocations of the cervicothoracic junction. J Spinal Disord Tech 2005;18:499–505 PubMed

4. An HS, Vaccaro A, Cotler JM, Lin S. Spinal disorders at the cervicothoracic junction. Spine 1994;19:2557– 2564 PubMed 5. Lenoir T, Hoffmann E, Thevenin-Lemoine C, Lavelle G, Rillardon L, Guigui P. Neurological and functional outcome after unstable cervicothoracic junction injury treated by posterior reduction and synthesis. Spine J 2006;6:507–513 PubMed

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Chapter 12  6. Wang VY, Chou D. The cervicothoracic junction. Neurosurg Clin N Am 2007;18:365–371 PubMed  7. Chen J, Eismont FJ. Cervicothoracic trauma: diagnosis and treatment. Semin Spine Surg 2005;17:84–90 8. Sapkas G, Papadakis S, Katonis P, Roidis N, Kontakis  G. Operative treatment of unstable injuries of the cervicothoracic junction. Eur Spine J 1999;8:279– 283 PubMed 9. Rao R. Neck pain, cervical radiculopathy, and cervical myelopathy: pathophysiology, natural history, and clinical evaluation. J Bone Joint Surg Am 2002;84-A: 1872–1881 PubMed 10. Kaneriya PP, Schweitzer ME, Spettell C, Cohen MJ, Karasick D. The cost-effectiveness of oblique radiography in the exclusion of C7-T1 injury in trauma patients. AJR Am J Roentgenol 1998;171:959–962 PubMed 11. Gelb DE, Hadley MN, Aarabi B, et al. Initial closed reduction of cervical spinal fracture-dislocation injuries. Neurosurgery 2013;72(Suppl 2):73–83 PubMed 12. Vaccaro AR, Hulbert RJ, Patel AA, et al; Spine Trauma Study Group. The subaxial cervical spine injury classification system: a novel approach to recognize the importance of morphology, neurology, and integrity of the disco-ligamentous complex. Spine 2007;32: 2365–2374 PubMed 13. Gertzbein SD. Scoliosis Research Society. Multicenter spine fracture study. Spine 1992;17:528–540 PubMed

14. Magerl F, Aebi M, Gertzbein SD, Harms J, Nazarian S. A comprehensive classification of thoracic and lumbar injuries. Eur Spine J 1994;3:184–201 PubMed 15. White AA, Panjabi MM. Clinical Biomechanics of the Spine, 2nd ed. Philadelphia: Lippincott; 1990 16. Cotler JM, Herbison GJ, Nasuti JF, Ditunno JF Jr, An H, Wolff BE. Closed reduction of traumatic cervical spine dislocation using traction weights up to 140 pounds. Spine 1993;18:386–390 PubMed 17. Karikari IO, Powers CJ, Isaacs RE. Simple method for determining the need for sternotomy/manubriotomy with the anterior approach to the cervicothoracic junction. Neurosurgery 2009;65(6, Suppl):E165–E166, discussion E166 PubMed 18. Kaya RA, Türkmenoğlu ON, Koç ON, et al. A perspective for the selection of surgical approaches in patients with upper thoracic and cervicothoracic junction instabilities. Surg Neurol 2006;65:454–463, discussion 463 PubMed 19. Boockvar JA, Philips MF, Telfeian AE, O’Rourke DM, Marcotte PJ. Results and risk factors for anterior cervicothoracic junction surgery. J Neurosurg 2001;94 (1, Suppl):12–17 PubMed 20. Resnick DK, Benzel EC. Lateral extracavitary approach for thoracic and thoracolumbar spine trauma: operative complications. Neurosurgery 1998;43:796– 802, discussion 802–803 PubMed

13 Cervical Trauma in Combination with Ankylosing Spondylitis or Diffuse Idiopathic Skeletal Hyperostosis Jorrit-Jan Verlaan and F. Cumhur Oner

■■ Introduction During assessment of a trauma patient in the emergency department, the cervical spine is protected until fractures or ligamentous disruptions have been identified or ruled out beyond a reasonable doubt.1 After completion of the primary survey and treatment of the immediate life-threatening injuries, attention may focus on the cervical spine. Following the integration of the principal information, including trauma mechanism, findings on the physical examination, and imaging studies, the presence or absence of clinically significant cervical injuries can typically be ascertained with a high level of confidence and reliability. Under some circumstances, however, the information needed to determine the degree of cervical injury can be misleading, resulting in a late or even an incorrect diagnosis and, subsequently, a suboptimal outcome. Specifically, for patients with ankylosis of the spinal column suspected of a cervical injury, the trauma mechanism and results obtained from physical and radiographical examination may be markedly different compared with a general trauma population.2,3 Spinal ankylosis is caused mainly by two distinct pathological processes: ankylosing spondylitis (AS) and diffuse idiopathic skeletal hyperostosis (DISH). The presence of both AS

and DISH is increasingly being recognized as an important modifier for the diagnostic workup, treatment, rehabilitation, and, ultimately, clinical outcome of trauma patients.4 This chapter discusses how AS and DISH may influence decision making during various critical phases, from the initial (prehospital) assessment to discharge and follow-up of patients with cervical injury.

■■ Etiology and Epidemiology

of Ankylosing Spinal Disorders

Ankylosing spondylitis and diffuse idiopathic skeletal hyperostosis are two well-defined but poorly understood disorders of the spinal column.5,6 Their common characteristic is progressive ankylosis (fusion of segments), although the underlying mechanism is different in each condition. AS is a systemic inflammatory dis­ order from the group of seronegative spondyloarthropathies, affecting the spinal column and, to a lesser extent, peripheral joints and nonskeletal structures. The key pathological feature of AS is the gradual destruction of articular cartilage in the sacroiliac and facet joints and obliteration of the intervertebral disk space,



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Chapter 13 leading to fusion of the spinal column and pelvic ring.5 The cascade of events leading up to articular destruction is largely unknown, although some studies point to a genetic basis of the disease. Typical symptoms associated with AS are pain, stiffness, and fatigue primarily ­located in the spine. AS is most often found in males, with the first symptoms occurring in the second or (less frequently) third decade of life, and it has an overall prevalence of 0.1 to 1.4%.5 As progression and expression of AS can be quite variable, a long latency period may be observed between the start of the disease and onset of the first symptoms. Diagnostic workup for suspected AS requires anteroposterior/lateral radiographs of the complete spinal column and pelvis, although early abnormalities may be found only on computed tomography (CT) or magnetic resonance imaging (MRI). The presence of clinical symptoms, demographic criteria, and radiographic signs of sacroiliitis (in the early stages of AS) or ankylosis of the sacroiliac joints and spinal column (in more advanced stages) usually confirms the diagnosis of AS. Treatment of AS is mostly symptomatic, although some drugs (nonsteroidal anti-inflammatory drugs, immunosuppressants, and tumor necrosis factor-α blockers) have been shown to decelerate progression of the disease.7 The hallmark of DISH, on the other hand, is progressive ossification of spinal and extraspinal ligaments while the articular surfaces are spared.8 DISH is most likely a systemic condition based on a low-grade inflammatory process with possible links to type 2 diabetes mellitus, atherosclerosis, and cardiovascular disease.6,9 The prevalence of DISH is highly variable (ranging between 2.9% and 30%) and depends on geographic location (possibly implying a genetic predisposition), selection bias, and the imaging modality used.10 Individuals affected by DISH are usually not aware of its presence because DISH is mostly without symptoms.6 Complaints somewhat specific for DISH include back pain, spinal stiffness, and dysphagia, the latter being present when large ossifications have developed in the anterior part of the cervical spine.11 To establish the diagnosis of DISH, the criteria from Resnick and Niwayama’s group8 are

most often used. They require the presence of flowing ossifications over at least four contiguous vertebral bodies without gross evidence of spondylosis, disk degeneration, or AS. CT is considered the gold standard imaging modality to diagnose DISH. As bone formation in DISH is, by definition, ubiquitous at the moment of diagnosis, treatment is mainly directed at relieving symptoms with the prescription of analgesics for spinal pain and dietary measures in cases with dysphagia.12 Rarely is resection of cervical ossifications necessary to ensure adequate intake of nutrition.11 As DISH is related to the metabolic syndrome, an increase in the number of cases is expected in the coming decades.

■■ Biomechanical Effects of

Spinal Ankylosis

As the healthy cervical spine is a flexible structure able to disperse traumatic energy over multiple levels, the amount of force needed for a fracture or ligament rupture to occur is substantial. In advanced stages of AS and DISH, this flexibility is lost.3 On lateral radiographs or sagittal reconstructions of CT scans, the changes directly affecting the biomechanical characteristics of the cervical spine in patients with AS and DISH can be easily appreciated. In AS, facet joints and the intervertebral disk space are obliterated and the cervical spine can therefore be regarded, from a biomechanical perspective, as a long bone.3 In DISH, ossifications develop mainly anteriorly from the cervical vertebral bodies in the anterior longitudinal ligament, although ossifications of the posterior longitudinal ligament, flavum ligament, and inter/supraspinal ligaments may also be observed.13 The facet joints and intervertebral disk spaces in DISH are (by definition) initially unaffected, but depending on the number of bridging ossifications, the cervical spine becomes progressively ankylosed. In advanced AS and DISH, some secondary effects of ankylosis emerge, including osteoporosis of the vertebral bodies as a result of stress shielding (although bone deposits in DISH may cause false normal

readings in bone mineral densitometry tests) and disuse atrophy of surrounding soft tissues.14,15 Long-standing AS or DISH may ultimately lead to a stiff, brittle neck, with local osteoporosis and a dysfunctioning soft tissue envelope. Moreover, fusion of multiple cervical levels creates long lever arms and, as a result, minor force is required to create damage-inducing torque.16 As has been demonstrated by several authors, most injuries in patients with ankylosis of the spinal column were caused by low-energy impacts, for instance, a fall from a sitting or standing position or a low-speed collision between motor vehicles.3 During impact, local energy peaks cause the cervical spine to fracture, largely comparable to a long bone (for

Fig. 13.1  Midsagittal reconstruction computed tomography (CT) scan of a 61-year-old man with ankylosing spondylitis after being hit by a car as pedestrian, showing clear hyperextension fracture with severe angulation and translation (C-type). The patient’s neurologic status was classified as American Spinal Injury Association (ASIA) grade A at admission.

Cervical Trauma in Combination example, a femur) with complete discontinuity between the fracture segments.17 As surrounding soft tissues are mostly dysfunctional (by atrophy or due to inclusion in the pathological process), ankylosed spine fractures easily dislocate primarily and secondarily and are thus inherently unstable (Figs. 13.1 and 13.2). Two types of fractures are frequently observed in the ankylosed spine: hyperextension fractures type B3 according to the recently published AO (Arbeitsgemeinschaft für Osteosynthesefragen) Spine classification system, and translation/ shear fractures (type C).17 These fractures can be located in the middle or at the extremes of multiple fused segments. According to the AO Spine classification, these highly unstable fracture types are preferably treated with surgical stabilization, as adequate reduction and immobilization may be difficult to achieve nonoperatively. Primary or secondary neurologic injury is common due to malalignment of the spinal canal following trauma or patient manipulation, respectively.3

Fig. 13.2  Midsagittal reconstruction CT scan of a 60-year-old man with diffuse idiopathic skeletal hyperostosis after missing the three lowest treads of a flight of stairs, resulting in a hyperextension fracture (B3 type) of C5. At admission the patient was neurologically intact.

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Chapter 13

■■ Prehospital Assessment

and Transportation of Patients with Cervical Ankylosed Spine Fractures

According to many modern trauma support protocols, establishing and maintaining a free airway and immobilization of the cervical spine are the very first steps a first responder should perform when managing a trauma patient.1 To immobilize the cervical spine, a rigid collar and accompanying head blocks/straps are applied and the patient is strapped tightly on a long spine board to protect the complete spinal column during transportation. Although this practice is generally accepted and may have prevented numerous cases of secondary worsening in the presence of unstable spine fractures, it can be harmful for patients with preexisting deformities or ankylosis of the cervical spine.3 Many patients with AS develop kyphosis in the cervicothoracic junction and thoracic spine during the course of their disease. Although less pronounced than in AS, patients with DISH may also develop fixed spinal deformities that cannot be addressed by active or passive postural reduction. For these patients, attempts to fixate the spine on a straight board may lead to discomfort or, in cases of acute fractures, to further fracture dislocation and, as a consequence, iatrogenic spinal cord injury. Some studies have reported the occurrence of spinal fractures and iatrogenic paraplegia in patients with AS as a result of patient positioning during elective surgery, and it is not unthinkable that immobilization on a spine board may also cause this type of injury.18 Transportation of trauma patients with (a suspicion of) spinal ankylosis on a spine board is suggested to be feasible and safe provided pre­ existing deformities are respected as much as possible and patients are supported and fixated in a comfortable position using adjuncts including vacuum mattresses, pillows, or sandbags.3 Trauma patients with cervical ankylosis who are unable to maintain a patent airway present a considerable challenge to emergency physicians.19 Many factors compounding a difficult endotracheal intubation are present in

patients with spinal ankylosis, including short neck, limited cervical range of motion or deformity, limited opening of the mouth, obesity, anterior cervical osteophytes, and possible cervical spine fracture. Physicians not proficient in doing difficult endotracheal intubation may better revert to bag-valve-mask ventilation until more experienced personnel and equipment (to attempt intubation with fiber optic devices, for example) are available. Neurologic deficits, varying from transient tingles in the extremities to complete tetraplegia, may frequently accompany ankylosed spine fractures. According to a recent study, 57% of patients with AS and 30% of patients with DISH had neurologic deficits at admission due to their spinal fracture.3 During initial (prehospital) assessment, a gross motor/sensory examination should be performed to establish (deficits in) function, as this clinical information is of great importance for guidance of the diagnostic workup and to determine surgical urgency.

■■ Treatment Principles in

Cervical Ankylosed Spine Fractures

Considering that the cervical spine in AS and DISH behaves similarly to a long bone, with respect to biomechanical characteristics, it may not be unreasonable to apply some principles of long bone fracture management to the injured ankylosed cervical spine.20 It is well established that for long bone fractures to heal, the integrity of surrounding soft tissues (which provide attachments to bone, supply nutrients, and form a barrier against microorganisms) is of great importance. Furthermore, for a fractured long bone to heal in an acceptable position, some sort of stability to the fracture fragments should be offered. In long bones, stabilization can be relative (when using plaster casts or intramedullary nails) or absolute (with compression plates), depending on the type of bone healing, direct or indirect, that is anticipated.20 In the presence of multiple fracture fragments, fracture fusion is usually through indirect bone healing with development of a fracture hema-



Cervical Trauma in Combination

toma and subsequent formation of callus. Regardless of the type of stabilization offered, fixation should be over a long trajectory to prevent implant failure due to screw pullout (or fracture dislocation in inadequate plaster casts in cases of nonoperative treatment), as lever arms are, by definition, large in long bones. The treatment of ankylosed cervical spine fractures is suggested to be similar to indirect long bone healing and requires relative stability by means of fixation points over a long trajectory in “bridging plate” fashion.20 As a rule of thumb, fractures should be instrumented over at least three segments cranially and three segments caudally to the fracture to avoid implant failure. The ideal instrumentation for ankylosed fractures of the cervical spine provides sufficient bone purchase on both sides of the fracture while avoiding stress risers at biomechanically vulnerable locations such as the cervicothoracic junction. Therefore, the authors often include the upper thoracic spine in the caudal part of the construction and shift the stress-riser–inducing extreme of the construction away from the junction while benefiting from the superior bone purchase of thoracic pedicle screws compared with (C7) cervical screws (Fig. 13.3). The consequent loss of motion at the cervicothoracic junction is of no concern in patients with AS and of minor consequence in patients with DISH due to preexistent ankylosis. Depending on bone quality, four to six lateral mass screws are typically used for the cranial part of the fracture to pro-

a

b

Fig. 13.3a–d  Images of the cervical spine of a 62-year-old man with ankylosing spondylitis after a fall from a standing position. (a) Lateral radiograph obtained at admission with kyphotic deformity showing at C5-C6. (b) Midsagittal reconstruction CT

vide sufficient purchase. Screws may be used in C1 according to the Harms technique and in C2 (pedicle screws). In the subaxial spine, we prefer to use lateral mass screws, as they are relatively safe, easy, and quick to use, even in the face of abnormal anatomy as frequently observed in AS and DISH, without the need for excessive soft tissue dissection or manipulation of the unstable cervical spine. Reduction of ankylosed cervical fractures may often be required, especially in the presence of neurologic deficits. Injury of the spinal cord in ankylosed fractures is typically the result of rotation or translation of the cranial part of the spinal segment relative to the caudal part, leading to malalignment instead of narrowing of the spinal canal as a result of bone fragment protrusion in, for example, burst-type fractures.21 As careful reduction results in realignment of the otherwise intact spinal canal, a complete decompression can be achieved in the majority of neurologically intact cases without the need for laminectomy. For patients with neurologic deficits or in cases with severe dislocation or locked fracture fragments requiring substantial unlocking reduction maneuvers, a laminectomy may be performed at the fracture level to provide decompression of the spinal cord and visual inspection during fracture reduction.22 In agreement with the principles of indirect fracture healing of long bones, ankylosed cervical spine fractures should be aligned and stabilized without compression or distraction.21 As spinal fractures in patients in

c

d

scan with translation of C5 relative to C6 and fusion of all visible segments except for C1. (c) Postoperative lateral radiograph showing long trajectory bridging from C3-T1. (d) Lateral radiograph at 1-year follow-up demonstrating fusion of C5-C6.

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Chapter 13 AS and DISH have a tendency to fuse fairly rapidly once stabilized, the use of autografts or synthetic bone fusion enhancers is normally not needed.

■■ Complications Related

to the Management of Cervical Ankylosed Spine Fractures

Several pitfalls can be identified in the treatment of ankylosed cervical fractures. First, the fracture needs to be recognized.23 Unfortunately, a patient’s delay in presenting for medical attention and a physician’s delay in diagnosing the condition both occur frequently. Patients with AS (and sometimes with DISH) have become used to experiencing episodes of spinal pain and do not always become alarmed after a trivial fall or accident, and as a result they seek medical help only after an increase in symptoms. Physicians are not always familiar with the radiographic abnormalities associated with AS and DISH, and may not recognize fractures on routine studies. Furthermore, ankylosed cervical spine fractures with a B3 type hyperextension configuration often hinge on a posteriorly located fulcrum and may close down when patients are lying supine and having their head supported by cushions.23 As a general rule, a physician needs to proactively rule out a fracture in patients with any signs of spinal ankylosis complaining of neck pain or spinal pain after suffering a traumatic event, however small. In some cases the fracture is visible only on MRI, and this modality should be used liberally, as the consequences of discharging a patient with a missed ankylosed spine fracture may be disastrous.24 A second common pitfall is secondary deterioration of neurologic function after hospital admission due to spinal cord injury caused by loss of spinal alignment.3 Every manipulation or transfer of the patient should be performed with maximum attention to maintaining alignment of the complete spinal column. The correct maneuver to transfer a patient or to change

a patient’s position is by using the log-roll technique. This technique requires at least three (but preferably more) well-instructed individuals for safe execution. Although halo-vest fixation of fractures of the ankylosed spine is not recommended as definitive treatment, it may be helpful in providing sufficient stabilization to decrease the risk of secondary neurologic deficit during manipulation or transfer of the patient. Furthermore, halo-vest fixation may be valuable while positioning the patient on the operating table and to maintain gross alignment during surgery. A third pitfall can be encountered during the final steps of surgical fixation of the an­ kylosed cervical spine. Preexistent deformities should be acknowledged and respected when fixating the cervical spine in its final position, as (over)correction of the, usually kyphotic, deformity may not be tolerated and could lead to iatrogenic spinal cord injury due to stretching or vascular compromise.24 Therefore, the surgeon should try to reconstruct the most probable pretrauma alignment of the cervical spine based on all radiographic studies (preferably also from an earlier date) and try to approximate this previous state when connecting rods to the implanted screws.

■■ Chapter Summary Ankylosis of the cervical spine is a relatively frequent finding caused by AS and DISH. As cervical segments become progressively fused, the flexibility of the neck decreases considerably, and the biomechanical characteristics of the cervical spine increasingly resemble that of long bones. As a result of stress shielding, the bone mineral density in the ankylosed spinal column is typically lower than in a control population. The combination of cervical ankylosis and poor bone strength results in a stiff and brittle neck susceptible to fracture after even minimal trauma. During transport and diagnostic workup, until definitive treatment can be started, great care should be taken to prevent further fracture dislocation and iatrogenic spinal cord injury. Fractures of the ankylosed

cervical spine can be difficult to diagnose due to preexisting abnormalities confounding interpretation of radiographic studies, inconclusive results due to insufficient/inappropriate imaging techniques, patient delay in presenting and physician delay in diagnosing, and underestimation of the traumatic impact. In patients with signs of ankylosis of the spinal column and with neck or back pain following (minor) trauma, physicians should have an extremely high index of suspicion for a ­spinal fracture. Treatment of fractures of the ankylosed cervical spine has some similarities with long bone fracture treatment principles. Surgical fixation is usually the treatment of choice, as indirect fracture stabilization (with halo-vest fixation or collar) is often insufficient and may lead to fracture dislocation, secondary neurologic deficits, or formation of pseudarthrosis. In general, long bridging-type constructs should be used to provide adequate stabilization at the fracture site while the instrumentation should preferably not end at vulnerable locations such as the cervicothoracic junction. The outcome of the management of patients with ankylosed cervical spine fractures depends mainly on their neurologic

Cervical Trauma in Combination status at admission and prevention of secondary neurologic injury. Pearls ◆◆ Maintain a high index of suspicion for cervical an-

kylosed spine fractures in every trauma patient with signs of spinal ankylosis and tenderness of the neck. ◆◆ Protecting the cervical spine is of extreme importance in patients with cervical ankylosed spine fractures until definitive treatment has been established. ◆◆ Treatment principles for cervical ankylosed spine fractures follow long bone fracture management to a large extent. ◆◆ Early mobilization and ambulation are key factors for good clinical outcome following cervical ankylosed spine fracture. Pitfalls ◆◆ Failure to recognize a cervical ankylosed spine

fracture may have disastrous consequences.

◆◆ Preexisting deformities should be respected

when immobilizing patients with (known) ankylosing disorders of the spine prior to transfer. ◆◆ Secondary neurologic deficits have great negative impact on ultimate clinical outcome and may often be avoidable.

References

Five Must-Read References 1. Navarro S, Montmany S, Rebasa P, Colilles C, Pallisera A. Impact of ATLS training on preventable and potentially preventable deaths. World J Surg 2014;38: 2273–2278 PubMed  2. Caron T, Bransford R, Nguyen Q, Agel J, Chapman J, Bellabarba C. Spine fractures in patients with ankylosing spinal disorders. Spine 2010;35:E458–E464 PubMed  3. Westerveld LA, van Bemmel JC, Dhert WJ, Oner FC, Verlaan JJ. Clinical outcome after traumatic spinal fractures in patients with ankylosing spinal disorders compared with control patients. Spine J 2014; 14:729–740 PubMed  4. Westerveld LA, Verlaan JJ, Oner FC. Spinal fractures in patients with ankylosing spinal disorders: a systematic review of the literature on treatment, neurological status and complications. Eur Spine J 2009;18: 145–156 PubMed 5. Braun J, Sieper J. Ankylosing spondylitis. Lancet 2007;369:1379–1390 PubMed

6. Mader R, Verlaan JJ, Buskila D. Diffuse idiopathic skeletal hyperostosis: clinical features and pathogenic mechanisms. Nat Rev Rheumatol 2013;9:741– 750 PubMed 7. van den Berg R, Stanislawska-Biernat E, van der ­Heijde DM. Comparison of recommendations for the use of anti-tumour necrosis factor therapy in ankylosing spondylitis in 23 countries worldwide. Rheumatology (Oxford) 2011;50:2270–2277 PubMed 8. Resnick D, Shapiro RF, Wiesner KB, Niwayama G, Utsinger PD, Shaul SR. Diffuse idiopathic skeletal hyperostosis (DISH) [ankylosing hyperostosis of Forestier and Rotes-Querol]. Semin Arthritis Rheum 1978;7:153–187 PubMed 9. Senolt L, Hulejova H, Krystufkova O, et al. Low circulating Dickkopf-1 and its link with severity of spinal involvement in diffuse idiopathic skeletal hyperostosis. Ann Rheum Dis 2012;71:71–74 PubMed 10. Westerveld LA, van Ufford HM, Verlaan JJ, Oner FC. The prevalence of diffuse idiopathic skeletal hyper-

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Chapter 13 ostosis in an outpatient population in The Netherlands. J Rheumatol 2008;35:1635–1638 PubMed 11. Verlaan JJ, Boswijk PF, de Ru JA, Dhert WJ, Oner FC. Diffuse idiopathic skeletal hyperostosis of the cervical spine: an underestimated cause of dysphagia and airway obstruction. Spine J 2011;11:1058–1067 PubMed 12. Sarzi-Puttini P, Atzeni F. New developments in our understanding of DISH (diffuse idiopathic skeletal hyperostosis). Curr Opin Rheumatol 2004;16:287– 292 PubMed 13. Verlaan JJ, Oner FC, Maat GJ. Diffuse idiopathic skeletal hyperostosis in ancient clergymen. Eur Spine J 2007;16:1129–1135 PubMed 14. Westerveld LA, Verlaan JJ, Lam MG, et al. The influence of diffuse idiopathic skeletal hyperostosis on bone mineral density measurements of the spine. Rheumatology (Oxford) 2009;48:1133–1136 PubMed 15. Diederichs G, Engelken F, Marshall LM, et al; Osteoporotic Fractures in Men Research Group. Diffuse idiopathic skeletal hyperostosis (DISH): relation to vertebral fractures and bone density. Osteoporos Int 2011;22:1789–1797 PubMed 16. Verlaan JJ, Westerveld LA, van Keulen JW, et al. Quantitative analysis of the anterolateral ossification mass in diffuse idiopathic skeletal hyperostosis of the thoracic spine. Eur Spine J 2011;20:1474–1479 PubMed 17. Vaccaro AR, Oner C, Kepler CK, et al; AOSpine Spinal Cord Injury & Trauma Knowledge Forum. AOSpine thoracolumbar spine injury classification system: fracture description, neurological status, and key modifiers. Spine 2013;38:2028–2037 PubMed

18. Danish SF, Wilden JA, Schuster J. Iatrogenic paraplegia in 2 morbidly obese patients with ankylosing spondylitis undergoing total hip arthroplasty. J Neurosurg Spine 2008;8:80–83 PubMed 19. Thompson C, Moga R, Crosby ET. Failed videolaryngoscope intubation in a patient with diffuse idiopathic skeletal hyperostosis and spinal cord injury. Can J Anaesth 2010;57:679–682 PubMed 20. Williams TH, Schenk W. Bridging-minimally invasive locking plate osteosynthesis (Bridging-MILPO): technique description with prospective series of 20 tibial fractures. Injury 2008;39:1198–1203 PubMed 21. Sapkas G, Kateros K, Papadakis SA, et al. Surgical outcome after spinal fractures in patients with ankylosing spondylitis. BMC Musculoskelet Disord 2009;10: 96–24 PubMed 22. Aoki Y, Yamagata M, Ikeda Y, et al. Failure of conservative treatment for thoracic spine fracture in ankylosing spondylitis: delayed neurological deficit due to spinal epidural hematoma. Mod Rheumatol 2013; 23:1008–1012 PubMed 23. Gilard V, Curey S, Derrey S, Perez A, Proust F. Cervical spine fractures in patients with ankylosing spondylitis: Importance of early management. Neurochirurgie 2014;60:239–243 PubMed 24. Elgafy H, Bransford RJ, Chapman JR. Epidural hematoma associated with occult fracture in ankylosing spondylitis patient: a case report and review of the literature. J Spinal Disord Tech 2011;24:469–473 PubMed

14 Rheumatoid Arthritis and Osteoporosis David T. Anderson

■■ Introduction Rheumatoid arthritis (RA) is a chronic, inflammatory autoimmune disorder characterized by symmetric erosive synovitis of the peripheral joints. It affects 1 to 2% of the world population and often entails early involvement of the cervical spine, affecting anywhere from 17 to 86% of patients.1 It can lead to progressive destruction of the synovial joints, ligaments, and bone in the cervical spine, particularly in the atlantoaxial segment. This progressive destruction can further lead to instability that generally follows three characteristic patterns, which may occur together or alone: atlantoaxial impaction (AAI), atlantoaxial subluxation (AAS), and subaxial subluxation (SAS). Each form of instability can in turn lead to spinal cord compression and neurologic symptoms.2–8 With the increased use of disease-modifying antirheumatic drugs (DMARDs), the need for surgical decompression and stabilization for cervical spine pathology due to RA has fallen.9,10 Nevertheless, the spine surgeon caring for patients with RA in the setting of cervical spine trauma must be aware of the specific challenges this patient population presents. Preexisting instability, neural compression, deformity, compromised bone quality, and impaired healing capabilities can all complicate the treatment of cervical spine trauma in patients with RA. Spine trauma centers should be encouraged to develop sound

treatment protocols to effectively treat these unique patients. Osteoporosis is a progressive bone disease characterized by loss of bone mass and density, deterioration of the microarchitecture of bone, and fragility fractures. It is a widespread disease that affects millions of elderly patients, both men and women, regardless of ethnicity. It leads to an increased risk of fractures of the hip, spine, and wrist, most notably. With the aging population, it is especially burdensome on health care systems. Osteoporosis is a relatively silent, asymptomatic disease until a fracture occurs, causing significant morbidity, mortality, and cost. It is estimated that 50% of women after age 50 and 20% of men after age 50 will sustain an osteoporotic fracture.11 Vertebral compression fractures are more common and occur earlier in the disease, but hip fracture risk increases exponentially with age. Vertebral compression fractures can lead to chronic back pain, progressive kyphosis, diminished quality of life, and increased utilization of medical resources.12 Osteoporosis generally results in thoracic and lumbar compression fractures. However, decreased bone mineral density in the elderly can also lead to characteristic fracture patterns of the cervical spine in the setting of even low-energy trauma. Odontoid fractures have recently received much attention due to the controversy that exists over optimal treatment.



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Chapter 14 Additionally, cervical vertebral body compression fractures and fracture dislocations at the cervicothoracic junction warrant attention because of the deformity they may create and the challenges that this region of the spine present. When treating these fractures, the surgeon must be acutely aware of the inherent difficulties in both nonsurgical as well as surgical management. Both are associated with risks of complications, morbidity, and death in the elderly population.

■■ Rheumatoid Arthritis Pathophysiology and Biomechanics Rheumatoid patients experience a cell-mediated immune response against soft tissue early, cartilage later, and bone last. A complex interplay of rheumatoid factor (an immunoglobulin M [IgM] antibody), mononuclear cells, interleukin-1 (IL-1), and tumor necrosis factor-α (TNF- α) results in a cascade of events, including antibody-antigen reactions, microvascular proliferation, and eventually hyperplasia of the synovium. This can lead to pannus formation, erosive joint and soft tissue destruction, and eventual subluxation and instability.2,4,7 The cervical spine has several separate synovial-lined joints. The occipitoatlantal and atlantoaxial articulations do not have intervertebral disks, and therefore their entire stability relies on these synovial joints and the complex ligamentous structures (transverse cruciate and alar ligaments) providing support. For this reason, the occipitoatlantal and atlantoaxial joints are most commonly affected. Three typical patterns of instability can develop. First, AAI is the result of rostral migration of the odontoid process due to destruction of articulation of the occipital condyles, the C1 lateral mass, and the C1-C2 lateral masses. This pattern is also called basilar invagination and cranial settling. This pattern can result in compression of the brainstem, and it may carry a poor prognosis. Usually diagnosed on lateral upright radiographs, several different proposed

measurements (McRae’s line, McGregor’s line, the Ranawat method, and others) have been developed over the years to make the diagnosis. The second pattern, AAS, is the most common form of instability in RA and is the result of destruction of the transverse ligament complex or erosion of the odontoid process, which in turn leads to abnormal anterior-posterior motion of the atlantoaxial articulation in flexion and extension. This is exacerbated in flexion and is manifested on lateral radiographs as an increase in the anterior atlanto-dens interval (AADI) greater than 5 mm and a decrease in the posterior atlanto-dens interval (PADI) to less than 14 mm.3 Repetitive compression of the upper cervical spinal cord in flexion can result in neurologic symptoms or injury. The third pattern, SAS, entails instability that is the result of synovial destruction of the facet joints, capsules, and weakening of the posterior ligamentous complex. From C3 to C7, there is progressive subluxation of one vertebral body on another that can result in the hallmark “staircase” on upright lateral radiographs (Fig. 14.1). This entity can be distinguished from degenerative spondylolisthesis by the lack of

Fig. 14.1  Rheumatoid arthritis. Involvement of the cervical spine typically results in progressive anterior subluxation of one vertebral body on the next, creating a “staircase” spine on standing lateral radiograph. Note the involvement of the C2–C3 and C3–C4 segments, not typically seen in the degenerative cervical spine.

osteophyte formation and by the frequent involvement of the C2–C3 and C3–C4 segments. Neural compression and subsequent symptoms can result. Again, flexion and extension views will determine the extent of subluxation. Space available for the cord (SAC) of less than 14 mm should alert the surgeon to pos­ sible cord compression.

Imaging The challenge in treating RA patients who present with trauma is to delineate preexisting deformity from new traumatic changes. RA patients may very well present with mild symptoms. At baseline, rheumatoid involvement of the cervical spine is often asymptomatic or may only include neck pain.1,2 It is important to understand that 40 to 80% of RA patients will have neck pain, and 43 to 86% will already have subluxation on radiographs; however, only 7 to 34% will have any neurologic deficits.2,3,8 A very complete history and physical exam should uncover any new symptoms, neurologic symptoms, and deficits. Upright radiographs should be obtained whenever possible. Most trauma centers now use computed tomography (CT) as a screening tool for head and neck trauma, which can demonstrate any obvious new fracture. Magnetic resonance imaging (MRI) should be obtained for any patient presenting with neurologic changes on physical examination. It also should be considered in the setting of basilar invagination on radiographs. MRI helps differentiate new traumatic injury from pre­ existing deformity, instability, or degeneration. More importantly, MRI displays an abnormal spinal cord signal, which may guide treatment. Trauma protocols have been established in most centers and should be closely followed. The Advanced Trauma Life Support (ATLS) guidelines aid the team in determining the presence of any life-threatening injuries, in addressing those injuries, and in uncovering any distracting injuries, regardless of an RA diagnosis. However, a thorough history should be taken, including questions about a prior diagnosis of RA. If the patient reports a prior diagnosis, this should immediately alert the treating team to pay close attention to more subtle symptoms

Rheumatoid Arthritis and Osteoporosis and signs on physical exam. All patients are assessed for distracting injures and neurologic status. CT of the cervical spine is standard screening protocol in most emergency departments. If any neurologic deficits are found, an MRI should be obtained. If the patient is neurologically intact and can stand, upright radiographs and flexion-extension views should be obtained at the discretion of the spine trauma team based on the findings on CT. It can be very helpful to obtain any prior radiographs, CT, or MRI if the patient has been seen and evaluated by a spine specialist prior to the trauma. These prior findings can help distinguish new trauma from existing deformity. During the clinical evaluation, patients should be assessed for pain and tenderness to palpation. Neck pain and occipital headaches are the most common symptoms in RA patients.1 Neurologic exam should uncover any deficits, myelopathic signs, weakness, gait disturbances, fine motor skill deficits, or paresthesias in the hands. It is paramount to obtain a good history and determine any preexisting symptoms.

Treatment Treatment of cervical spine fractures should adhere to the standard of care for the specific fracture pattern identified. Nonoperative treatment for relatively stable fracture patterns may be indicated. Immobilization in a hard cervical orthosis or halo vest is a reasonable option, but halo vest utilization in the elderly seems to be falling out of favor due to the high rate of associated complications.13 Unstable fracture patterns, injuries with continued spinal cord compression, and incomplete neurologic injuries may require surgical stabilization eventually with decompression. Spine surgeons should adhere to the Subaxial Cervical Spine Injury Classification (SLIC) guidelines.14 If surgical treatment of a RA patient with comorbid cervical spine trauma is indicated, the treating surgeon should strongly consider the use of anterior and posterior fixation due the poor bone quality often encountered in RA patients. One approach or the other, used alone, may be at high risk of failure. Again, this patient population can present challenges and

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Chapter 14 obstacles in the form of osteoporotic bone, preexisting deformity or stenosis, medical comorbidities, functional limitations, and relative activity of the disease itself. The risks and benefits of surgery must be thoroughly evaluated and discussed with the patient and family. The ultimate goal of surgical intervention is to decompress any cord compression, stabilize any instability, and restore alignment. Presurgical halo traction can be utilized to aid in this goal. The patient may require several days of traction before surgery is attempted. With the multitude of bone grafting options and instrumentation available, every attempt should be made to achieve a solid arthrodesis. Meticulous fusion bed preparation, careful placement of rigid instrumentation, and strong consideration of the use of autografts will aid in the fusion. In addition, the treating surgeon should consider longer postoperative immobilization than for a typical patient without RA. The three specific patterns of instability in the RA patient with trauma should be treated accordingly. In the RA patient with SAS, a SAC of less than 14 mm, and dynamic instability on flexion-extension radiographs, an anterior/ posterior procedure should be considered. If the instability is not reducible, the anterior approach should be done first to restore sagittal alignment, followed by posterior instrumented fusion. In the RA patient with AAS, a SAC of less than 14 mm, cord compression, and dynamic instability, consideration should be given to a posterior C1–2 arthrodesis. If the instability is fixed, laminectomy may be required. In the RA patient with AAI and cord compression, surgery may be indicated. Traction followed by an occipital-cervical fusion is a reasonable choice. If the deformity is fixed, a C1 laminectomy may be required.

■■ Osteoporosis Pathophysiology Osteoporosis is a systemic disease that eventually reduces the mechanical strength of bone. Essential in preventing osteoporosis is the achievement of normal peak bone mass, which

occurs in the third decade of life. Proper nutrition, appropriate calcium and vitamin D intake, regular menstrual cycles, and a regular exercise program all contribute to overall bone health. After menopause, women undergo ­accelerated bone loss without the protective effects of estrogen. After the age of 50, women and men gradually lose bone mass.11 The National Osteoporosis Foundation has identified and published patient characteristics that may predict poor bone quality. They include a history of previous fragility fracture or a fracture in a first-degree relative, Caucasian ethnicity, smoking, low body mass index, female gender, dementia, poor health, and fragility.15 Bone quality can be assessed with plain ­radiographs and CT, but is better evaluated with a dual-energy radiograph absorptiometry (DEXA). A T-score of 1 to 2.5 standard deviations below the value for healthy 25-year-old controls is considered osteopenia. Osteoporosis is defined as greater than 2.5 standard deviations below the control. DEXA scans can closely follow bone quality during medical treatment of osteoporosis, and can provide information that may aid in the elective treatment of spine pathology. It is not routinely obtained in the setting of trauma, however. Osteoporosis affects the cancellous portion of bone earlier and, only in the later stages, affects cortical bone. The weight-bearing vertebral bodies of the anterior column of the spine consist largely of cancellous bone covered by a thin cortical shell. Conversely, the posterior elements of the spinal column contain larger quantities of cortical bone and are mechanically stronger. Osteoporosis affects the microarchitecture of the cancellous bone, and therefore fractures are more prone in these areas under higher stress with less mechanical strength.16

Fracture Patterns Osteoporotic compression fractures typically occur in the midthoracic region (T5–T8) and the thoracolumbar junction (T10-L2). The mid­ thoracic vertebrae are the region of the most kyphosis and have increased load on the anterior column and weaker cancellous bone in flexion. The thoracolumbar junction represents

a straight section of the spine where there is a transition from a relatively stiff thoracic spine (due to the added stability of the rib cage) to a mobile lumbar spine. This makes the region susceptible to complex forces, most notably including axial compression, leading to failure of the anterior column and compression and burst-type fractures. Alignment and the effects of arthrosis also play a role in the osteoporotic compression fracture patterns in the aging spine. Areas of lordosis typically are protected due to the compressive forces being transmitted through the more cortical bone-rich posterior elements; compression fractures of the cervical spine and lumbar spine are therefore seen less often. Additionally, degenerative changes and arthrosis can lead to sclerosis of the subchondral bone and have an overall protective effect. Often the older patient exhibits both osteoporosis and degenerative changes concomitantly. In regard to the cervical spine, there are two fracture patterns that typically develop as a result of the overall clinical picture of weak osteoporotic bone, stiff arthritic segments, and possible upper thoracic kyphosis. Fractures at the atlantoaxial complex and fractures of the cervicothoracic junction require special attention. Fractures at the C1-C2 articulation in the osteoporotic spine are often the result of relatively low-energy falls. The elderly spine can often assume a hyperkyphotic thoracic region, which is accompanied by a compensatory hyperlordotic upper cervical segment. Additionally, the unique anatomy of the C2 vertebral body puts the odontoid at risk in these falls. There is also a high proportion of cancellous bone in the C2 body and a horizontally oriented joint at C1-C2. This allows considerable motion at the C1-C2 articulation but puts stress on the odontoid process, especially in accidental falls. There has long been significant controversy over the management of odontoid fractures in the elderly. Fractures at the cervicothoracic junction can also be seen in the osteoporotic spine with low-energy trauma. In the setting of hyper­ kyphosis of the upper thoracic spine, the cervicothoracic junction can be put in a position that predisposes it to more compressive forces,

Rheumatoid Arthritis and Osteoporosis as well as shear forces, in trauma. Although traditionally difficult to image, the cervicothoracic junction is now easily evaluated with the readily available and quick CT scan in the emergency department. Again, the transition from relatively stiff thoracic segments to the more mobile cervical spine can put the vertebral bodies of C7 and T1 at risk for fractures in the elderly population.

Treatment and Surgical Strategies Management of cervical spine trauma should adhere strictly to the ATLS guidelines, with identification of any life-threatening conditions and distracting injuries, a thorough history, and a neurologic exam. Evaluation of the elderly patient with high- or low-energy trauma often includes a CT scan of the cervical spine. The treating surgeon must be aware of the inherent changes in bony architecture and alignment that puts particular areas of the cervical spine at risk in this patient population. In the osteoporotic and stiff spine, clinicians should maintain a high index of suspicion for injuries at the atlantoaxial junction and the cervicothoracic junction. The workup should include an MRI if there is any neurologic deficit. In most trauma centers, an MRI will be obtained if a fracture is identified as well. Plain radiographs in the weight-bearing position, if possible, can also aid in the treatment choice. As mentioned previously, the treatment of geriatric type II odontoid fractures has been the subject of intense debate for years. More recently, the AO (Arbeitsgemeinschaft für Osteosynthesefragen) Spine North America organization has closely studied nonoperative versus operative treatment in a multicenter study with a large number of patients.17–19 Odontoid fracture management, regardless of treatment choice, is inherently difficult and can result in multiple complications, significant morbidity, and even mortality. Type I and type III odontoid fractures are typically treated nonoperatively with hard collar immobilization. Type II fractures (Fig. 14.2) present a challenge due their higher rate of nonunion.17–20 Nonoperative treatment options include hard cervical orthosis or halo vest immobilization. Again, the halo

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Fig. 14.2  Type II geriatric odontoid fracture in the setting of osteoporosis. A relatively minor trauma in an elderly patient resulted in this fracture pattern. Note the stiff, spondylotic, and osteoporotic cervical spine.

vest immobilization has fallen out of favor in the elderly population due to the high rate of complications and general patient intolerance.13,20 However, it is a reasonable option in a younger patient without risk factors for nonunion. A hard cervical orthosis is the most common option for nonoperative treatment. It may not result in a bony union of the fracture, but a fibrous union may provide sufficient stability. In the AO Spine study, 36% of patients underwent conservative care. Of those, 81% were treated in a hard collar, 9% in a soft collar, and 10% in halo vest immobilization.17 Operative treatment can be considered in the patient with risk factors for nonunion who is otherwise a suitable surgical candidate. Additionally, displaced fractures and nonunions with instability are indications for surgical ­intervention. Practices seem to vary widely across trauma centers. Surgical approaches include an anterior odontoid screw or posterior

C1–C2 arthrodesis (Fig. 14.3). Transoral resection of the odontoid and posterior stabilization is reserved for rare cases. In the AO Spine study, 64% of patients underwent operative fixation of a type II odontoid fracture. Of those, 79% underwent posterior C1–C2 fusion with screw fixation, 12% underwent anterior odontoid screw fixation, and the remainder underwent posterior fusion with various wiring or screw fixation techniques. In this study, operative treatment was associated with a higher union rate, relatively equivalent complication rate, and an overall better outcome. Initial nonoperative treatment, male gender, older age, and neurologic impairment were associated with failure of treatment. Follow-up studies confirmed that, regardless of treatment, the 1-year mortality rate was relatively high at 18%.19 Additionally, 22% of those patients initially treated nonoperatively developed symptomatic nonunions, and over 60% of those patients required delayed



Rheumatoid Arthritis and Osteoporosis quire operative fixation to regain adequate alignment and stability. Compression fractures typically occur at the lower levels of the cervical spine and may be accompanied by a hyperkyphotic upper thoracic spine, making access anteriorly difficult. Flexion-extension films should provide the treating surgeon with enough information to decide if an anterior approach is feasible. Strong consideration should be given to a combined anterior-posterior approach to obtain a rigid construct and a solid arthrodesis.

■■ Chapter Summary

Fig. 14.3  Type II geriatric odontoid fracture. A suitable candidate for surgical intervention, this patient was treated with posterior C1-C2 fusion. Anatomic limitations required the use of trans­ laminar screws at C2.

surgical fixation.18 These studies represent the most robust literature we have at this point regarding the treatment of geriatric odontoid fractures. Again, they highlight the inherent difficulty in treating these fractures that are often partially the result of osteoporotic bone. As the population ages, the spine surgeon treating these injuries must closely weigh the risks and benefits of treatment options and provide this information to the patient and family when jointly making decisions regarding treatment. Fractures at the cervicothoracic junction also present challenges in the osteoporotic spine. Failure of the anterior column in this region can lead to an increase in kyphosis of the upper thoracic region and possibly chin-on-chest deformities. Additionally, fractures in this region are often mechanically unstable and may re-

Rheumatoid arthritis is a chronic, proliferative autoimmune disease with early involvement of the cervical spine. Although surgery for cervical spine deformities has become less frequent with the use of DMARDs, the spine surgeon treating cervical trauma must be aware of the challenges inherent in this difficult patient population. Cervical trauma protocols should be closely followed, regardless of a preexisting diagnosis of RA. However, the spine surgeon must be acutely aware of the multiple problems often encountered when treating cervical spine trauma in these patients. Again, the difficulty lies in distinguishing preexisting deformity from new trauma. Careful history regarding new symptoms is very important. When surgery is indicated, strong consideration should be given to combined anterior and posterior fixation to aid in fusion. Every attempt should be made to achieve near-normal anatomic alignment as well and prevent development of any neurologic decline. Lastly, the surgeon needs to be aware of the challenges in the postoperative recovery of these patients in regaining function. Osteoporosis is a progressive bone disease characterized by loss of bone mass and density, deterioration of the microarchitecture of bone, and fragility fractures. Compression fractures of the midthoracic and thoracolumbar regions are the most common form of spine fractures encountered, but special attention must be paid to the osteoporotic spine in the setting of

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Chapter 14 cervical spine trauma. Preexisting deformity of the upper thoracic region and upper cervical region accompanied by a relatively stiff spine create characteristic fractures of these two regions. Proper workup and identification of potential challenges will aid the treating surgeon in dealing with these fractures. Regardless of treatment choice, these fractures generally represent a poor prognosis for the patient. When operative treatment is indicated, special consideration must be given to fixation in weak bone. Careful technique, prolonged immobilization, close follow-up, and good rehabilitation are important in achieving a solid arthrodesis and overall recovery.

◆◆ Early involvement of the medical team and the

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Pearls ◆◆ ◆◆ Strict adherence to sound surgical techniques

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can help avoid surgical complications. However, when treating RA patients, the surgeon must be ready to deal with complications in this challenging patient population. The risk of pseudarthrosis can be mitigated with meticulous preparation of fusion bed, careful placement of rigid instrumentation, and the use of autograft with allograft extenders. Prolonged collar immobilization or the possible use of the halo vest in select patients can help in achieving a solid arthrodesis. The recovery and rehabilitation of RA patients after cervical spine surgery is often prolonged. A strong rehabilitation and physical therapy team is paramount. Patients may have functional limitation due to limb deformities, in addition to any preexisting myelopathic symptoms. Early involvement of the physical medicine and rehabilitation team is helpful. The treating surgeon must be acutely aware of the inherent difficulties in treating fractures of the cervical spine that present in osteoporotic patients. Preexisting deformity, including hyperkyphotic thoracic segments, compensatory hyperlordotic cervical segments, and stiff spines, all can make treatment difficult. Patients with osteoporosis often present with other comorbidities that must be taken into ­account when discussing treatment options. A careful assessment of overall health and risk stratification is important.

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physical medicine and rehabilitation team is helpful in transitioning the patient from initial injury, through treatment, and ultimately to a rehabilitation program. Identification of specific needs and proper assistive devices can facilitate functional recovery and avoid medical problems. When treating type II odontoid fractures with operative fixation, meticulous preparation of fusion surfaces is paramount in achieving a successful union. Careful attention must be paid to preoperative imaging to determine the feasibility of various screw trajectories. Longer and thicker screws afford better purchase and therefore more rigid fixation. C2 pedicle screws should be favored over the shorter C2 pars screw, but may not be feasible based on the vertebral artery pathway. Strong consideration should be given to anterior/ posterior approaches when dealing with the cervicothoracic junction due to the higher stresses in this region. Longer constructs may be necessary to achieve mechanical stability.

Pitfalls ◆◆ The RA patient may have several medical co-

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morbidities that can have a negative impact in the setting of undergoing cervical decompression and stabilization. It is important to have the medical team closely involved in the treatment plan. Active RA disease and the DMARDs used to treat it can be difficult to manage. The skin of RA patients can cause wound healing problems. Regardless of treatment choice, management of osteoporotic fractures entails considerable risk of complications. Construct failure and screw pullout may be avoided with prolonged immobilization in a collar for C1-C2 fractures. Consideration should be given to a custom-­ molded cervicothoracic brace in the setting of operative fixation in this region. If loss of fixation is identified at the cervicothoracic junction, revision surgery with re-instrumentation and extension of the construct may be required.



Rheumatoid Arthritis and Osteoporosis

References

Five Must-Read References 1. Rawlins BA, Girardi FP, Boachie-Adjei O. Rheumatoid arthritis of the cervical spine. Rheum Dis Clin North Am 1998;24:55–65 PubMed 2. Kim DH, Hilibrand AS. Rheumatoid arthritis in the cervical spine. J Am Acad Orthop Surg 2005;13:463– 474 PubMed  3. Boden SD, Dodge LD, Bohlman HH, Rechtine GR. Rheumatoid arthritis of the cervical spine. A longterm analysis with predictors of paralysis and re­ covery. J  Bone Joint Surg Am 1993;75:1282–1297 PubMed 4. Pellicci PM, Ranawat CS, Tsairis P, Bryan WJ. A prospective study of the progression of rheumatoid ­arthritis of the cervical spine. J Bone Joint Surg Am 1981;63:342–350 PubMed 5. Ranawat CS, O’Leary P, Pellicci P, Tsairis P, Marchisello  P, Dorr L. Cervical spine fusion in rheumatoid arthritis. J Bone Joint Surg Am 1979;61:1003–1010 PubMed 6. Nurick S. Pathogenesis of spinal cord disorders. Brain 1972;95:87–100 PubMed 7. Zeidman SM, Ducker TB. Rheumatoid arthritis. Neuroanatomy, compression, and grading of deficits. Spine 1994;19:2259–2266 PubMed 8. Youseff JA, Forsythe SL, Glover N, Patterson AJ. Rheumatoid arthritis. In: Vaccaro AR, Anderson P, eds. Cervical Spine Trauma. Philadelphia: Rothman Institute; 2010 9. Kauppi MJ, Neva MH, Laiho K, et al; FIN-RACo Trial Group. Rheumatoid atlantoaxial subluxation can be prevented by intensive use of traditional disease modifying antirheumatic drugs. J Rheumatol 2009; 36:273–278 PubMed 10. Mallory GW, Halasz SR, Clarke MJ. Advances in the treatment of cervical rheumatoid: Less surgery and less morbidity. World J Orthod 2014;5:292–303 PubMed

11. Lane JM, Russell L, Khan SN. Osteoporosis. Clin Orthop Relat Res 2000;372:139–150 PubMed 12. Cumhur Oner F. Osteoporosis. In: Vaccaro AR, Anderson P, eds. Cervical Spine Trauma. Philadelphia: Rothman Institute; 2010 13. Majercik S, Tashjian RZ, Biffl WL, Harrington DT, Cioffi WG. Halo vest immobilization in the elderly: a death sentence? J Trauma 2005;59:350–356, discussion 356–358 PubMed 14. Joaquim AF, Patel AA, Vaccaro AR. Cervical injuries scored according to the Subaxial Injury Classification system: an analysis of the literature. J Craniovertebr Junction Spine 2014;5:65–70 PubMed 15. Heinemann DF. Osteoporosis. An overview of the National Osteoporosis Foundation clinical practice guide. Geriatrics 2000;55:31–36, quiz 39 PubMed 16. White AA, Panjabi MM. Clinical Biomechanics of the Spine. Philadelphia: Lippincott; 1978:31 17. Chapman J, Smith JS, Kopjar B, et al. The AOSpine North America Geriatric Odontoid Fracture Mortality Study: a retrospective review of mortality outcomes for operative versus nonoperative treatment of 322 patients with long-term follow-up. Spine 2013;38:1098–1104 PubMed 18. Smith JS, Kepler CK, Kopjar B, et al. Effect of type II odontoid fracture nonunion on outcome among elderly patients treated without surgery: based on the AOSpine North America geriatric odontoid fracture study. Spine 2013;38:2240–2246 PubMed 19. Fehlings MG, Arun R, Vaccaro AR, Arnold PM, Chapman JR, Kopjar B. Predictors of treatment outcomes in geriatric patients with odontoid fractures: AOSpine North America multi-centre prospective GOF study. Spine 2013;38:881–886 PubMed 20. Lewis E, Liew S, Dowrick A. Risk factors for nonunion in the non-operative management of type II dens fractures. ANZ J Surg 2011;81:604–607 PubMed

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15 Pediatric Cervical Spine Ahmet Alanay and Caglar Yilgor

■■ Introduction This chapter discusses cervical spinal injury in children, which is somewhat different from that in adult patients, due to differences in an­ thropometrics, biomechanics, clinical presen­ tation, and management principles. Although an infrequent entity, because of the high rates of associated morbidity and mortality, the di­ agnosis should be quickly and accurately made. The epidemiology, developmental anatomy, and normal variants by age that complicate the ­interpretation of findings in these patients are explained in this chapter. Mechanisms and patterns of injury, clinical and radiological cer­ vical spine clearance, treatment strategies, and possible complications are described.

■■ Epidemiology Cervical spine injury in children is rare, rep­ resenting a small percentage of all pediatric traumas. However, those who sustain injury have a high morbidity and mortality in com­ parison with adult patients. More than 60% of spinal injuries in children are in the cervical spine. Spinal cord injury with transient or per­ manent neurologic injury is common. About half of these injuries do not demonstrate ra­ diographic evidence of bony involvement. Chil­

dren younger than 8 years of age are less likely to sustain fractures and are at greater risk for cord injuries. One third to one half of all children with cervical injuries demonstrate neurologic defi­ cits; 75% of these are incomplete and the rest are complete. The mortality rate ranges from 16 to 18%. However, due to their greater heal­ ing potential, surviving children have superior outcomes when compared with adults, with up to 90% partial and 60% complete recovery.1 Sixty percent of injuries occur in boys, with a bimodal distribution that peaks at age 2 to 4 years and 12 to 15 years. The most commonly identified injury type among all ages is iso­ lated ligamentous injury. Even in children older than 10 years of age, 20% of injuries are purely ligamentous. The spinal column shows significant differ­ ences between infants (0 to 2 years), young children (>2 to 8 years), and older children (>8 years) related to the proportionality of the head to the spine, bone composition, vertebral body shape, development of neck musculature, inclination of facet joints, and ligamentous laxity. Furthermore, the presence of synchon­ droses confers increased susceptibility to shear forces. The younger the child, the more likely the injury involves the upper cervical spine. Lower cervical injuries are associated with a higher percentage of spinal cord trauma, whereas upper cervical injuries have higher rates of mortality,

with atlanto-occipital dislocation having the highest. Motor vehicle accidents, with their impact on vehicle occupants, pedestrians, and bicycle riders, are the most common source of injury. Falls and sports injuries account for up to 30% of injuries in younger children and older chil­ dren, respectively. Nonaccidental trauma is also found in smaller numbers that often present with associated injuries to the head, thorax, abdomen, and musculoskeletal system. Conditions such as Down syndrome, muco­ polysaccharidosis or spondyloepiphyseal dys­ plasia, and congenital anomalies including dysraphism and os odontoideum can predis­ pose children to cervical spine and cord injury.

■■ Mechanism of Injury Cervical spine injuries are caused by flexion, extension, lateral flexion, compression, distrac­ tion, and rotation, and by the simultaneous or sequential effects of these factors. For example, the nonaccidental trauma due to vigorous shak­ ing would occur secondary to flexion-extension and rotation-type moments. Hyperflexion injuries include flexion tear­ drop fracture, wedge (compression) fractures, uni- and bilateral facet subluxation/dislocations, anterior subluxation, and spinous process frac­ tures. Spinous process fractures, unilateral facet fractures, and some anterior subluxations are considered stable, whereas the rest are unstable. The mechanism of injury in hyperextension is often a blow to the face or forehead. Hyper­ extension injuries include avulsion of the ante­ rior arch of C1, isolated fracture of the posterior arch of C1, hyperextension teardrop fracture, hyperextension dislocation, lamina fracture, and traumatic spondylolysis of C2 (Hangman’s fracture).2 The hyperextension teardrop is a result of avulsion of the anterior longitudinal ligament. Although it is more frequent at C2 in adults, in children it is more common in the subaxial spine and is often associated with spinal cord injury and prevertebral soft tissue swelling.

Pediatric Cervical Spine Axial compression forces can result in the Jefferson fracture of the atlas or the burst frac­ ture in the lower cervical spine. This mecha­ nism is especially dangerous if it occurs with the neck slightly flexed because it brings the spinal alignment into a straight line where the normal force distribution is disturbed and the neck musculature cannot assist with shock absorption. Rotation injuries occur usually in combina­ tion with flexion or extension forces and are often associated with vertebral artery injury. Lateral flexion injuries are relatively uncommon, and include lateral vertebral body compression fracture, uncinate and transverse process frac­ ture, and occipital condyle fracture.2 Other types of injuries such as atlanto-­occipital dis­ sociation, atlantoaxial injuries, and odontoid fractures do not result from a single mecha­ nism and are due to a combination of forces. Inappropriate or inadequate restraint within motor vehicles may increase the rates and se­ verity of injury. Placing small children in adult three-point seat belts result in an imbalance between their proportionately larger head and restraint of the torso, causing injury due to hy­ perflexion of the neck.

Associated Injuries Approximately half of the patients have other associated traumatic injuries. Injury to the head is the most common associated injury seen in up to 40% patients, and is associated with a lower Glasgow Coma Scale score and higher mortality, and with spinal cord injury. Other commonly associated injuries include solid organ and abdominal wall injuries, and skeletal injuries such as pelvic and extremity fractures. Thoracic and vascular trauma may be less fre­ quently present. Although multilevel spinal injuries may be identified in up to 40% of the patients, multi­ level cervical spinal injury is uncommon, with only 1% of more than one level of dislocation, and 3% of fractures involving more than one cervical vertebra.3 Injuries to the spinal cord at C3-C5 may re­ sult in phrenic nerve failure with subsequent

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Chapter 15 apnea or hypoventilation. Spinal shock can also affect the cardiovascular system, leading to hypotension or bradycardia. Hence, attention should be paid to breathing and circulation in a child with suspected cervical injury.

■■ Developmental Anatomy

and Embryology

Most vertebrae originate from four primary ossification centers: one in each hemi-arch and two within the centrum. Longitudinal and cir­ cumferential growth occurs in the chondro­ epiphyseal portions. Longitudinal growth is the result of enchondral ossification, whereas cir­ cumferential growth is due to perichondral and periosteal apposition. Through a separate posterior growth plate at the spinous process synchondrosis, posterior elements also demon­ strate longitudinal growth. Ossification of the anterior arch of the atlas begins between the third month and first year of life. Ossification of the posterior arch is com­ pleted by the age of 3 years. The synchondroses between the body and the posterior elements fuse by 7 years of age.4 The axis has two additional ossification centers that fuse in the midline to form the odontoid process. The body and the odontoid fuse between ages 3 and 6 years, yet the fusion line might remain visible throughout the life.4 There is a secondary ossification center at the apex of the odontoid that appears and fuses between the ages of 6 and 12 years. Failure of fusion results in persistent ossiculum termi­ nale, which should be differentiated from os odontoideum. Another secondary ossification center at the inferior epiphyseal ring appears at puberty and fuses with the body by age 25 years.4 The development of the subaxial cervical spine is similar from C3 to C7. The central part ossifies first, and the arches fuse in the midline between the ages of 3 and 6 years. Secondary ossification centers are located at the anterior transverse processes, spinous process apices, and superior and inferior epiphyseal rings.4

■■ Normal Anatomic,

Biomechanical, and Radiological Variations

It is important to understand the changing anatomy of the pediatric cervical spine to in­ terpret injury patterns and distinguish injury from a large number of normal variants. Al­ though it varies with age, in general, the fol­ lowing anatomic differences in children are frequently seen: • The facet joints are more shallow and horizontal. • The interspinous ligaments, joint capsules, and cartilaginous end plates are more stretch­ able without tearing. • The uncinate process, which restricts rota­ tional and lateral movements, is absent in children younger than 10 years of age. • Vertebral bodies are wedge shaped and spi­ nous processes are not fully developed. Biomechanical variations arise from the fact that the immature spine is more elastic. The skeletal elements are far more stretchable than the neural elements; thus, posttraumatic my­ elopathy, even without any evident injury to the vertebral column, is much more common in children than adults. This also exhibits the underlying cause for the phenomenon called spinal cord injury without radiographic abnor­ mality (SCIWORA). This entity is discussed in detail later in this chapter. Other biomechani­ cal variations in children are the following: • Subaxial hypermobility is present, due to the aforementioned anatomic traits, and is more prominent in children under 8 years of age. • The inherent hypermobility of the pediatric spine results in a higher fulcrum of motion at C2-C3. This fulcrum shifts caudally to­ ward C5-C6 by the age of 10, subsequently resulting in more adult-like injury patterns in older children and adolescents.5 • The atlanto-occipital joint is less stable in children due to physiological ligamentous laxity, the presence of synchondroses, more



Pediatric Cervical Spine planar C1 lateral masses and smaller occipi­ tal condyles that increase the joint’s suscep­ tibility to translational injury.

On both plain radiographs and computed tomography (CT), synchondroses may be mis­ taken for fracture lines. Secondary ossification centers, bifid spinous processes, and unfused ring apophyses can mimic traumatic injury. Conversely, fractures through synchondroses may be misinterpreted as within the realm of normal. Therefore, familiarity with the average ages of appearance and fusion, and with the types of growth plates and secondary ossifi­ cation centers is essential. Growth plates are in general symmetrical and have smooth and sclerotic borders. Common normal radiological variations are as follows: ◆◆ Pseudosubluxation or pseudolisthesis is com-

◆◆ ◆◆

◆◆

◆◆

monly observed in the upper cervical vertebrae before the age of 8 years, with anterior displacement of C2 on C3, and to a less common degree of C3 on C4. It may be present in up to 20% of normal children. Pseudosubluxation is differentiated from a true instability with the use of posterior cervical (Swischuk’s) line.6 A line is drawn to connect anterior cortical borders of the spinous processes of C1 to C3 on a true lateral radiogram. If the anterior cortical border of the spinous process of C2 is > 2 mm away from this line, a true anteriorly displaced C2 is suggested. The loss/absence of cervical lordosis can be seen in children up to 16 years of age. Wedging of immature vertebral bodies up to 3 mm may be present below C2 until ~ 8 years of age. This is due to the ovoid appearance with vertebral interspaces equivalent to the height of the vertebral bodies and should not be confused with compression fractures. With increasing age, the vertebral bodies adopt a more rectangular shape. However mild C3 wedging can persist until the age of 12 years.7 The atlanto-dens interval (ADI) is the distance between the anterior aspect of the dens and the posterior aspect of the anterior ring of the atlas. ADI may be increased in children, and values up to 4.5 or 5 mm are accepted to be within the normal range. In adults, a noteworthy prevertebral space would often suggest edema or hemorrhage resulting from cervical injury. A widened retropharyngeal

space up to 6 mm may be observed as a thickened prevertebral shadow on plain radiographs in children. This is related to expiration, especially if the child is crying. When in doubt, repeat radiography performed in mild extension and inspiration may be used to distinguish between normal variations and abnormal findings. ◆◆ Synchondroses of C2 may be misinterpreted for fractures. The apical odontoid synchondrosis may appear as separations in children between 6 and 12 years of age. The dens–C2 body synchondrosis may be mistaken for a type II dens fracture. In contrast, the most common injury involving the odontoid process in children younger than 6 years of age is a fracture through this particular synchondrosis, which may be missed. Dorsal tilting of the dens is normal, whereas ventral tilting is not. ◆◆ Pseudo-Jefferson fracture may be seen in openmouth odontoid views of children up to 7 years of age, and is particularly common in children younger than 4 years of age. This phenomenon describes the appearance of spread of the atlas on the axis where the lateral masses can displace as much as 6 mm from the dens, which is due to the discrepancy in the growth rate of the atlas compared with the axis.

■■ Cervical Spine Clearance Prehospital Considerations Immediate in-the-field cervical immobilization of patients with multisystem trauma, a blunt injury above the clavicle, or a suspicious mech­ anism of injury, or of patients presenting with a neurologic deficit or an altered level of con­ sciousness, is likely essential to prevent repet­ itive spinal cord or spinal column injury. All patients should be treated as though they have an unstable spine until proven otherwise. Therefore, immobilization of the cervical spine before clinical or radiographic clearance is the standard of care. Because of the proportionately large head in younger children, immobilization should be done with either a backboard with a recess for the occiput or a standard backboard with pads placed under the torso to eliminate back­ board-induced flexion and partial airway ob­

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Chapter 15 struction. A rigid cervical collar and sandbags used in combination with the straps of the backboard is most effective in limiting cervical spine motion. Yet it should be kept in mind that immobilization can be problematic in a fright­ ened or combative child. Plus, cervical collars may lead to supraphysiological distraction. Thus, although three-point immobilization re­ mains the aim, manual inline immobilization as tolerated may be more appropriate in such circumstances. If cervical spine injury is suspected, direct transport to a pediatric trauma center should be considered. However, if the closest center requires traveling long distances, local hospi­ tals may provide important interventions to stabilize the patient prior to transport.

Assessment of the Risk of the Patient and Diagnostic Recommendations Clearance of the pediatric cervical spine can be done using clinical, radiographic, and ad­ vanced imaging data. It is dependent on an ­accurate assessment of the degree of risk to the individual child. To date, there are no vali­ dated prediction rules that are derived from children. Instead, the adult data are generally extrapolated. Clinical clearance requires a synthesis of his­ tory, presentation, and physical examination. In the setting where the child is alert and as­ ymptomatic, and can be considered low risk using several criteria, the cervical spine can be cleared. But in the child who cannot be consid­ ered low risk, the consensus on the method of clearance is less clear. The first goal of clearance is to stratify the child into one of the following categories: (1) low risk, (2) conscious but not low risk, and (3) unconscious or obtunded. The National Emergency X-Radiography Utilization Study (NEXUS)8 identified five cri­ teria to determine if the risk is low: (1) no mid­ line cervical tenderness on direct palpation, (2) normal alertness, (3) no evidence of in­ toxication, (4) no neurologic abnormality, and (5)  no painful or distracting injuries. Use of

these criteria was estimated to reduce the need for pediatric spinal imaging by up to 20%. How­ ever, the NEXUS study includes few children under the age of 9 and no children under the age of 2 years with spinal cord injury. There­ fore, care must be taken in the extrapolation of results to these subgroups.8 Some authors advocate adding a sixth criteria: the ability to appropriately communicate verbally.9 Pain-free range of motion and the mechanism of injury may also be considered when deciding on the need for imaging.10 In a more recent study, cervical spine imag­ ing was not recommended in children over the age of 3 years who are alert; have no neuro­ logic deficit, midline cervical tenderness, or painful distracting injury; do not have unex­ plained hypotension; and are not intoxicated.11 In another study of children in this age group, imaging was not recommended in children who have a Glasgow Coma Scale score > 13; do not have a neurologic deficit, midline cervical tenderness, or painful distracting injury; are not intoxicated; do not have unexplained hy­ potension; and did not sustain an injury in a motor vehicle accident, a fall from a height > 3 m (10 feet), or a nonaccidental trauma as a known or suspected mechanism of injury.11 Al­ though prehospital immobilization is currently recommended, trained prehospital providers may also safely implement these low-risk cri­ teria to prevent unnecessary interventions. Conscious children who do not meet the low-risk criteria require immobilization and further investigation. Lee et al12 proposed a 10-criteria tool for immobilization and radio­ graphic evaluation that includes similar points to those discussed above. There is no clear consensus on the method of clearance for unconscious or obtunded chil­ dren. National Institute for Health and Care Excellence (NICE) recommends computed to­ mography (CT) scanning of head and cervical spine within 1 hour of presentation.13 The use of magnetic resonance imaging (MRI) in this subgroup of patients facilitates earlier clear­ ance and a shorter intensive care unit (ICU) and overall hospital stay. For children who are likely to remain unconscious beyond 48 hours, or for whom clearance is unlikely to be obtained

within 72 hours, MRI is recommended.14 In this report, MRI altered the diagnosis in 34% from that obtained from plain radiographs or CT, and 23% of the children with normal radiographs had abnormal findings on MRI. However, it is very unlikely that a patient who is normal or has a stable injury pattern that demonstrates abnormal MRI findings will eventually develop instability.

Use of Plain Radiographs in Clearing the Pediatric Cervical Spine Anteroposterior and lateral views, oblique ra­ diographs, flexion and extension films, openmouth odontoid images, and radiographs taken under slight traction are options that may be used for cervical spine clearance. Among these views, the lateral image, in which the external auditory canals and the lower cervical facets are superimposed, has the highest sensitivity for cervical spine injury. Oblique radiographs and odontoid view add little diagnostic value to conventional radio­ graphs in the pediatric population, particularly in younger children or children who are less cooperative. An odontoid view may not be nec­ essary for cervical spine clearance for children younger than 8 years of age. Formerly, flexion and extension radiographs were used for evaluation of the neurologically intact patients with normal initial radiographs but a persistence of spinal tenderness. This dynamic evaluation of cervical stability should best be performed with an active range of mo­ tion, which is usually limited due to muscle spasm and pain. Also, these children should not be subjected to passive flexion and exten­ sion that poses a risk for further injury. Because flexion and extension films have not been shown to be clearly beneficial, and because MRI is now more widely available, these films have fallen out of favor. MRI can detect all the changes that would be found on dynamic films, whereas flexion and extension films might miss several ligamentous injuries that are iden­ tified on MRI. The current trend is to use dy­ namic images 2 to 3 weeks later in the follow-up

Pediatric Cervical Spine evaluation of a previously detected ligamen­ tous injury that is associated with possible instability. A radiograph under slight traction can fur­ ther illustrate the disruption of the diskoliga­ mentous structures. The use of such films has also fallen out of favor for similar reasons. Skeletal development makes the interpreta­ tion of roentgenograms age dependent. Careful evaluation of the interspinous distances, disk spaces, and neuroforamina is necessary at each level. The use of Swischuk’s line and the ADI was described above. Another measure, the Powers ratio, is the distance from the tip of the basion to the pos­ terior arch of the atlas, divided by the distance from the opisthion to the posterior aspect of the anterior arch of the atlas. A ratio > 0.9 sug­ gests atlanto-occipital dislocation. Two other measures, the Wackenheim cli­ vus line and the rule of thirds, may also be used to determine atlantoaxial instability (AAI). The Wackenheim line is drawn along the posterior cortical margin of the clivus, which should in­ tersect the odontoid or be tangential to it. It suggests AAI if it does not intersect. The rule of thirds states that the dens and the spinal cord should each fill one third of the canal space, and the final third should be free. Normal values for other measurements that might be useful for determining ligamentous injury are as follows: • Basion-dens interval (BDI) < 10.5 mm in CT (unreliable in age 5 mm an­ terior displacement with bilateral anterior facet dislocations. • Type IV is a posterior displacement of the axis on the atlas and is rare. Initial management consists of 1 to 4 weeks of cervical traction followed by 4 to 6 weeks of immobilization. Delays in the diagnosis and treatment lead to C1-C2 adherence, and are related with increased rates of irreducibility, a  greater chance of recurrence, higher rates of C1-C2 motion loss, and greater need for sur­ gical stabilization. Fig. 15.1 demonstrates the management of a 16-year-old patient with AARS who was treated with halo traction and immobilization.

Odontoid Fracture C2 has the most numerous synchondroses, and has by far the highest incidence of synchondro­ sis injury. Fractures of the odontoid are rela­ tively common and typically occur through the synchondrosis at the base of the odontoid. Small children secured in forward-facing car seats have sustained this injury pattern. Pa­ tients are usually neurologically intact. In gen­ eral, this epiphyseal injury may have an intact periosteal sleeve, increasing the likelihood of successful reduction and healing with immobi­ lization in extension.

Lower Cervical Spine Injury Although relatively uncommon, fracture, frac­ ture/dislocation, dislocation, and purely liga­ mentous injury may be seen, usually in children over 9 years of age. In neurologically intact patients, the initial management should be done with emergent manual reduction followed by external immo­ bilization. Immediate MRI should follow to de­ termine the presence of an epidural hematoma or herniated disk. Some of these patients may require surgery due to irreducibility or on an emergent basis to treat compressive pathology within the spinal canal.

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a

b

c

d

e

f

Fig. 15.1a–f  A 16-year-old patient with atlantoaxial rotatory subluxation. (a) Coronal, (b) axial 15-mm maximum intensity projection, and (c) three-­ dimensional (3D) reconstruction images. (d) Coronal,

(e) axial 15-mm maximum intensity projection, and (f) 3D reconstruction images of the same patient after halo traction and immobilization, showing complete reduction.



SCIWORA Pang and Wilberger18 first defined this entity in 1982 as neurologic signs or symptoms with no radiographic abnormality. Advances in im­ aging led to a change in definition, whereby plain films and CT findings are normal, but MRI displays pathological findings such as cord edema, paraspinal muscle edema or hemor­ rhage, epidural or subdural hematomas, cord hemorrhage, ligamentous disruption, disk edema or herniation, and complete cord transection. The basis for the existence of SCIWORA is that the spinal column can stretch up several centimeters before rupture and can display a transient displacement with subsequent re­ alignment, whereas the spinal cord that is teth­ ered superiorly and inferiorly is damaged after several millimeters of traction. Although delayed onset of several days has been reported, closer analysis often shows transient neurologic symptoms at or near the time of initial trauma or subtle neurologic defi­ cits that were missed in the initial physical examination. There are some clinical and radiographic findings that may be helpful in determining prognosis. Severity and completeness of injury generally correlates with the outcome. Chil­ dren with complete lesions rarely improve. Children with severe, incomplete lesions im­ prove, but are unlikely to regain full function. In comparison, children with mild to moderate deficits improve, and some achieve full recov­ ery. Age and the location of injury may also help to determine the prognosis. SCIWORA is more likely to occur at upper levels and be more severe in children younger than 8 years of age, and at lower levels and be less severe in older children. MRI can be a better predictor of outcome than neurologic status alone. The absence of spinal cord signal changes on T2weighted images indicates an excellent progno­ sis. Minor hemorrhage and edema only predicts a favorable outcome. Major hemorrhage and complete spinal cord disruption suggest severe and possibly permanent injury. Typically, SCIWORA is managed with 12 weeks of external immobilization followed by 12 weeks of activity modification to allow lig­

Pediatric Cervical Spine amentous injuries to heal, and to prevent recurrence.

Sports Injuries Sports-related injuries are the second most common cause of cervical spine injury in chil­ dren older than 10 years of age and in adoles­ cents. Soft tissue injuries resulting from direct trauma include sprains and strains. Common findings are midline tenderness, muscle spasm, and loss of range of motion with intact neu­ rology. Management consists of cervical im­ mobilization and medical therapy with gradual return to sports activities. The injury that causes stinging or burning that spreads from the shoulders to the hand after injuries in contact or collision sports are called “burners” or “stingers.” The transient weakness resulting from brachial plexus trac­ tion typically involves only one arm and lasts up to 30 minutes. Most of these injuries do not require treatment and resolve within a few minutes or several days. Recurrent burners and stingers may require working with a trainer or therapist. If the injury results in spinal cord concus­ sion, also known as cervical cord neurapraxia, the sensory and motor symptoms may involve both arms, both legs, or all four extremities. Patients are managed with 2 weeks of cervical immobilization in a hard cervical collar fol­ lowed by dynamic films.

Neonatal Injuries Infants with birth-related cervical spine and spinal cord injuries present with flaccidity and absence of spontaneous motion; these injuries are associated with cephalic presentation and the use of forceps. The upper cervical spine is most susceptible to injury. External custom-­ made immobilization spanning from the oc­ ciput to the thorax may be used.

C2 Fracture Bilateral fractures of the pars interarticularis of C2 leading to traumatic spondylolisthesis are rare in children. Differentiating this injury from

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Chapter 15 synchondroses in young children can be diffi­ cult and may require advanced imaging.

Os Odontoideum A well-corticated odontoid process that lacks continuity with the C2 body is called os odon­ toideum. It may be associated with atlantoaxial instability and myelopathy. In general, the be­ lief is that the risks of untreated os odontoi­ deum outweigh the risks of C1-C2 fusion.

■■ Treatment Strategies Although some patients will require hospital­ ization or an ICU stay, most pediatric cervical spine injuries can be treated conservatively. Surgery is generally indicated for unstable in­ juries, irreducible fractures or dislocations, pro­ gressive neurologic deficits, or deformities due to epidural hematoma, disk protrusion, or cord compression. With the advance of fixation sys­ tems and techniques recently, more and more surgeons prefer to electively treat patients sur­ gically if halo immobilization is to be used for a long time, given the hazards of prolonged im­ mobilization in children. Due to the paucity of data on the use of meth­ ylprednisolone specific to pediatric patients, coupled with the controversy surrounding its administration, steroids are not considered a standard procedure and are used at the discre­ tion of the treating physician. Halo immobilization may safely be used in children as young as 7 months old. Due to the thin calvaria before the age of 5, stable fixation requires more pins with less torque to decrease the risk of skull penetration. Weight should be administered cautiously with close neurologic monitoring, because of the increased risk of overdistraction due to ligamentous laxity and underdeveloped musculature. Minor complica­ tions, such as pin site infections are common. Cervical instrumentation in children has satisfactory results with low complication rates. The cartilaginous nature and small size of the anatomy demand great accuracy in the place­ ment of screws. Manipulation during intuba­ tion must be done rigorously in the child with

unstable cervical spine to prevent additional spinal cord injury. The patient should be turned with a cervical collar, and a radiograph should be obtained prior to prepping to confirm that no change in position occurred during transfer. The iliac crest, ribs, or calvarial grafts may be used to achieve fusion. Commercially available bone grafts, demineralized bone matrix, or bone substitutes may still maintain the rates of fusion while reducing harvest related morbid­ ity. Wound closure is important, and soft tis­ sues should adequately cover bulky implants to allow for proper healing. Occipitocervical fusion can be achieved with threaded contoured rods and wiring. Plate-rod constructs coupled with C1-C2 transarticular screws or C2 pedicle screws may also be used. Atlantoaxial fusion may be achieved by poste­ rior wiring using several graft types or using rod-screw constructs. Subaxial stabilization may be attained via an anterior or posterior ap­ proach. Pedicle or lateral mass screws can be used for posterior instrumented fusion. Short stature and low-profile anterior plates are ap­ propriate for anterior fusion.

■■ Outcomes and Late

Complications

Although outcomes are generally favorable due to the greater healing potential of children, most children having cervical spinal cord injury ­before their growth spurt will develop spinal deformities. Such deformities are paralytic or neuromuscular in nature, and should be ad­ dressed accordingly. Posttraumatic syringomy­ elia can develop due to residual kyphosis or canal stenosis after remodeling. Such patients may present with an upward-creeping neuro­ logic level and increased spasticity. The results of shunt surgeries are not always very satisfying.

■■ Chapter Summary Cervical spine injury in children is rare, repre­ senting a small percentage of all pediatric trauma patients. The most commonly identi­

fied injury type among all ages is isolated liga­ mentous injury. However, those who sustain injury have a high morbidity and mortality in comparison to adults. Motor vehicle accidents are the most common cause of injury. Spinal cord injury with transient or permanent neu­ rologic injury is common; however, children have better outcomes due to their greater heal­ ing potential. Approximately half of the pa­ tients have other associated traumatic injuries. It is important to understand the changing anatomy of the pediatric cervical spine to in­ terpret injury patterns and distinguish injury from a large number of normal variants. Im­ mediate in-the-field cervical immobilization is essential to prevent repetitive spinal cord or spinal column injury. Clearance of the pediatric cervical spine can be done using clinical, radio­ graphic, and advanced imaging data. Antero­ posterior and lateral plain radiographs should be the first-line screening tool whenever clini­ cal clearance cannot be achieved. CT should be used judiciously to manage the child with the lowest possible radiation exposure. MRI is rec­ ommended for all patients with an abnormal neurologic examination and for patients requir­ ing special investigation of their soft tissues and spinal cord. Most pediatric cervical spine injuries can be treated conservatively. Surgery is generally indicated for unstable injuries, irreducible frac­ tures or dislocations, progressive neurologic deficits, or deformities. Halo immobilization may safely be used in children. Cervical instrumen­ tation in children has satisfactory results with low complication rates. Although outcomes are

Pediatric Cervical Spine generally favorable due to greater healing po­ tential of children, some children having cervi­ cal spinal injury before their growth spurt will develop spinal deformities. Pearls ◆◆ Cervical spinal injuries represent a small percent-

◆◆ ◆◆

◆◆

◆◆

◆◆

age of all pediatric traumas, but they entail high morbidity and mortality. Associated spinal, head, and other injuries are seen in approximately half of the patients. The changing anatomy of the pediatric cervical spine should be understood to facilitate interpreting injury patterns and distinguish injury from a large number of normal variants. Although immediate in-the-field cervical immobilization is currently recommended, trained prehospital providers may also safely implement the low-risk criteria. When a halo is to be applied, more pins with less torque should be used to decrease the risk of penetration of the thin calvaria. Cervical instrumentation in children has satisfactory results with low complication rates.

Pitfalls ◆◆ Odontoid view radiographs may be inconclusive

for children under the age of 8 years.

◆◆ A widened retropharyngeal space may not indi-

cate edema or hemorrhage, especially if the child is crying. ◆◆ Normal initial radiographs do not exclude spinal injury. The spinal column can stretch up several centimeters and display a transient displacement with subsequent realignment, whereas the spinal cord is damaged after several millimeters of traction.

References

Five Must-Read References  1. Easter JS, Barkin R, Rosen CL, Ban K. Cervical spine injuries in children, part I: mechanism of injury, cli­ nical presentation, and imaging. J Emerg Med 2011; 41:142–150 PubMed 2. Junewick JJ. Cervical spine injuries in pediatrics: are children small adults or not? Pediatr Radiol 2010; 40:493–498 PubMed   3. Leonard JR, Jaffe DM, Kuppermann N, Olsen CS, Leo­ nard JC; Pediatric Emergency Care Applied Research

Network (PECARN) Cervical Spine Study Group. Cer­ vical spine injury patterns in children. Pediatrics 2014;133:e1179–e1188 PubMed 4. Fesmire FM, Luten RC. The pediatric cervical spine: developmental anatomy and clinical aspects. J Emerg Med 1989;7:133–142 PubMed 5. d’Amato C. Pediatric spinal trauma: injuries in very young children. Clin Orthop Relat Res 2005;432:34– 40 PubMed

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Chapter 15 6. Swischuk LE. Anterior displacement of C2 in children: physiologic or pathologic. Radiology 1977;122:759– 763 PubMed 7. Eubanks JD, Gilmore A, Bess S, Cooperman DR. Clear­ ing the pediatric cervical spine following injury. J Am Acad Orthop Surg 2006;14:552–564 PubMed 8. Viccellio P, Simon H, Pressman BD, Shah MN, Mower WR, Hoffman JR; NEXUS Group. A prospective multi­ center study of cervical spine injury in children. Pe­ diatrics 2001;108:E20 PubMed 9. Gore PA, Chang S, Theodore N. Cervical spine injuries in children: attention to radiographic differences and stability compared to those in the adult patient. Semin Pediatr Neurol 2009;16:42–58 PubMed 10. Chung S, Mikrogianakis A, Wales PW, et al. Trauma association of Canada Pediatric Subcommittee Na­ tional Pediatric Cervical Spine Evaluation Pathway: consensus guidelines. J Trauma 2011;70:873–884 PubMed 11. Rozzelle CJ, Aarabi B, Dhall SS, et al. Management of pediatric cervical spine and spinal cord injuries. Neu­ rosurgery 2013;72(Suppl 2):205–226 PubMed 12. Lee SL, Sena M, Greenholz SK, Fledderman M. A mul­ tidisciplinary approach to the development of a cer­

vical spine clearance protocol: process, rationale, and initial results. J Pediatr Surg 2003;38:358–362, dis­ cussion 358–362 PubMed 13. National Institute for Health and Care Excellence. Head injury guidance (CG176). http://www.nice.org .uk/guidance/CG176. Accessed November 27, 2014 14. Flynn JM, Closkey RF, Mahboubi S, Dormans JP. Role of magnetic resonance imaging in the assessment of pediatric cervical spine injuries. J Pediatr Orthop 2002;22:573–577 PubMed 15. Ramrattan NN, Oner FC, Boszczyk BM, Castelein RM, Heini PF. Cervical spine injury in the young child. Eur Spine J 2012;21:2205–2211 PubMed 16. Sun PP, Poffenbarger GJ, Durham S, Zimmerman RA. Spectrum of occipitoatlantoaxial injury in young children. J Neurosurg 2000;93(1, Suppl):28–39 PubMed 17. Phillips WA, Hensinger RN. The management of ro­ tatory atlanto-axial subluxation in children. J Bone Joint Surg Am 1989;71:664–668 PubMed 18. Pang D, Wilberger JE Jr. Spinal cord injury without radiographic abnormalities in children. J Neurosurg 1982;57:114–129 PubMed

16 The New AOSpine Subaxial Cervical Spine Injury Classification System Gregory D. Schroeder, Paul W. Millhouse, Alexander R. Vaccaro, F. Cumhur Oner, and Luiz Roberto Vialle

There are two main goals of an injury classification system. The first is to facilitate accurate communication between health care professionals, including treating physicians, trainees, and researchers. The second is to guide the treatment of the injury. The utility of classification systems in orthopedic trauma vary significantly, with some well-designed classifications, such as the Schatzker classification for tibial plateau fractures,1,2 being used for over 40 years, whereas classification systems of other injuries are constantly replaced. In 1951, Böhler3 published the first major classification of injuries to the spinal column, but as the knowledge of spinal anatomy, biomechanics, and physiology improved, these early spinal injury classifications proved to be inadequate. This has led to many iterations of subaxial cervical spine injury classifications. In 1970, Holdsworth4 published a mechanistic classification for the entire spine based on his observation of over 2,000 patients with spinal injuries. This was the first major classification to define stable and unstable injuries, and to recognize the biomechanical importance of the posterior ligamentous complex. In an effort to improve upon this classification, the Allen and Ferguson and their group5 later created a more detailed mechanism-based classification, which divided fractures into six major types: compressive flexion, vertical compression, distractive flexion, compressive extension, distractive extension, and lateral flexion. De-

spite the apparent simplicity of this classification, it has poor reliability and limited clinical relevance.6 Further modifications were made to this system by Harris et al,7 who changed the mechanisms to include flexion, flexion and rotation, hyperextension and rotation, vertical compression, extension, and lateral flexion; however, these changes complicated the system without improving the clinical relevance. Understanding the limitations of the previous classifications and using a similar methodology as was used in the development of the Thoracolumbar Spine Injury Classification System (TLICS), Vaccaro et al8 developed the Subaxial Injury Classification (SLIC) and Severity Scale in 2007. This classification simplified the morphological category into three basic types: compression, distraction, and rotation/translation. Additionally, it was the first classification of subaxial cervical spine injuries to formally consider the integrity of the diskoligamentous complex and the neurologic status of the patient. Finally, the SLIC system assigned a point value to the morphology of the injury, the integrity of the diskoligamentous complex, and the neurologic status of the patient. An injury score was determined based on the summation of the value for each variable, and this score could be used to propose appropriate treatment algorithms. In spite of initial reports of acceptable reliability,8 a more recent independent validation study reported poor interobserver reliability for fracture morphology (k = 0.29),



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Chapter 16

Fig. 16.1  Subtype A0. Minor bony injury that does not affect stability, such as a spinous/transverse process fracture; additionally, this subtype can be used for neurologic injuries without a fracture, such

as a central cord injury. (From Vaccaro AR, Koerner JD, Radcliff KE, et al. AOSpine subaxial cervical spine injury classification system. Eur Spine J 2015 Feb 26 [Epub ahead of print]. Reproduced with permission.)

and only moderate reliability for the integrity of the diskoligamentous complex (k = 0.46).9 Furthermore, because the classification was designed by a select group of surgeons with limited global input, it has been criticized for fostering the views of its creators and recommending treatments that may not be consistent with the local treatment practices. Lastly, magnetic resonance imaging (MRI) is often needed to assess the integrity of the diskoligamentous complex, and this is not readily available in many parts of the world. Because of the aforementioned concerns with previous subaxial cervical spine injury classifi-

cations, in 2015 AOSpine published the new AOSpine Subaxial Cervical Spine Injury Classification System. The new classification separates fractures into three major morphological types10: • Type A: Compression injury (Figs. 16.1, 16.2, 16.3, 16.4, 16.5) • Type B: Injury to the anterior or posterior tension band (Figs. 16.6, 16.7, 16.8) • Type C: Translational injury (Fig. 16.9) Additionally, type A and B fractures are further subcategorized (Table 16.1) similar to the AOSpine Thoracolumbar Classification system.11

Fig. 16.2  Subtype A1. Compression fractures involving a single end plate without involvement of the posterior wall of the vertebral body. (From Vaccaro AR, Koerner JD, Radcliff KE, et al. AOSpine subaxial cervical spine injury classification system. Eur Spine J 2015 Feb 26 [Epub ahead of print]. Reproduced with permission.)

Fig. 16.3  Subtype A2. Coronal split fracture that involves both end plates but not the posterior wall. (From Vaccaro AR, Koerner JD, Radcliff KE, et al. AOSpine subaxial cervical spine injury classification system. Eur Spine J 2015 Feb 26 [Epub ahead of print]. Reproduced with permission.)



The New AOSpine Subaxial Cervical Spine Injury Classification System

Fig. 16.4  Subtype A3. Incomplete burst fracture involving one end plate and the posterior wall. (From Vaccaro AR, Koerner JD, Radcliff KE, et al.

AOSpine subaxial cervical spine injury classification system. Eur Spine J 2015 Feb 26 [Epub ahead of print]. Reproduced with permission.)

Fig. 16.5  Subtype A4. Complete burst fracture involving both end plates and the posterior wall. (From Vaccaro AR, Koerner JD, Radcliff KE, et al.

AOSpine subaxial cervical spine injury classification system. Eur Spine J 2015 Feb 26 [Epub ahead of print]. Reproduced with permission.)

171



172

Chapter 16 Fig. 16.6  Subtype B1. Transosseous disruption of the tension band. (From Vaccaro AR, Koerner JD, Radcliff KE, et al. AOSpine subaxial cervical spine injury classification system. Eur Spine J 2015 Feb 26 [Epub ahead of print]. Reproduced with permission.)

Fig. 16.7  Subtype B2. Any injury that disrupts the posterior ligamentous tension band. (From Vaccaro AR, Koerner JD, Radcliff KE, et al. AOSpine subaxial cervical spine injury classification system. Eur Spine J 2015 Feb 26 [Epub ahead of print]. Reproduced with permission.)

Fig. 16.8  ubtype B3. Any injury that disrupts the anterior ligamentous tension band. (From Vaccaro AR, Koerner JD, Radcliff KE, et al. AOSpine subaxial

cervical spine injury classification system. Eur Spine J 2015 Feb 26 [Epub ahead of print]. Reproduced with permission.)



The New AOSpine Subaxial Cervical Spine Injury Classification System Fig. 16.9  Type C. Translational injury. (From Vaccaro AR, Koerner JD, Radcliff KE, et al. AOSpine subaxial cervical spine injury classification system. Eur Spine J 2015 Feb 26 [Epub ahead of print]. Reproduced with permission.)

Table 16.1  Subtypes of Fracture Types A and B for the New AOSpine Subaxial Cervical Spine Injury Classification System Type

Definition 

A A0

Compression Injury Minor bony injury that does not affect stability such as a spinous/transverse process fracture; additionally, this can be used for neurologic injuries without a fracture such as a central cord injury in the setting of a spondylotic spine Wedge fracture that involves a single (usually superior) end plate and does not disrupt the posterior wall Coronal split fracture that involves both end plates both not the posterior wall Incomplete burst fracture involving one end plate and the posterior wall Complete burst fracture involving both end plates and the posterior wall Tension band injury Transosseous disruption of the tension band Any injury that disrupts the posterior ligamentous tension band Any injury that disrupts the anterior ligamentous tension band

A1 A2 A3 A4 B B1 B2 B3

173



174

Chapter 16 Next, injuries to the facet joints are classified separately (Table 16.2; Figs. 16.10, 16.11, 16.12, 16.13), and the neurologic status of the patient is evaluated (Table 16.3). Lastly, patient-­ specific modifiers, if appropriate, are assigned (Table 16.4).

An initial reliability analysis of the classification yielded promising results, with good interobserver reliability reported for morphological subtypes (k = 0.64).10 A worldwide reliability study is ongoing. Additionally, multiple international studies are being performed on

Table 16.2  Grading of the Facet Injury for the New AOSpine Subaxial Cervical Spine Injury Classification System Injury

 Definition

F1 F2 F3 F4 BL

A nondisplaced fracture that is less than < 1 cm in height and involves  1 cm in height or involving > 40% of the lateral mass Floating lateral mass Any fracture that results in a subluxed, perched, or dislocated facet Bilateral facet involvement

Fig. 16.10  Subtype F1. A nondisplaced fracture that is less than < 1 cm in height and involves < 40% of the lateral mass. (From Vaccaro AR, Koerner JD,

Radcliff KE, et al. AOSpine subaxial cervical spine injury classification system. Eur Spine J 2015 Feb 26 [Epub ahead of print]. Reproduced with permission.)

Fig. 16.11  Subtype F2. Any displaced fracture or a fracture > 1 cm in height or involving > 40% of the lateral mass. (From Vaccaro AR, Koerner JD, Radcliff KE, et al. AOSpine subaxial cervical spine injury classification system. Eur Spine J 2015 Feb 26 [Epub ahead of print]. Reproduced with permission.)



The New AOSpine Subaxial Cervical Spine Injury Classification System

Fig. 16.12  Subtype F3. Floating lateral mass. (From Vaccaro AR, Koerner JD, Radcliff KE, et al. AOSpine subaxial cervical spine injury classification system.

Eur Spine J 2015 Feb 26 [Epub ahead of print]. Reproduced with permission.)

Fig. 16.13  Subtype F4. Any fracture that results in a subluxed, perched, or dislocated facet. (From Vaccaro AR, Koerner JD, Radcliff KE, et al. AOSpine subaxial cervical spine injury classification system. Eur Spine J 2015 Feb 26 [Epub ahead of print]. Reproduced with permission.)

Table 16.3 Grading for the Neurologic Status of the Patient for the New AOSpine Subaxial Cervical Spine Injury Classification System Status

Definition 

N0 N1

Neurologically intact Neurologic symptoms that have completely resolved Persistent radiculopathy/nerve root injury Incomplete spinal cord injury Complete spinal cord injury Unable to obtain a neurologic exam Ongoing compression of the spinal cord

N2 N3 N4 Nx +

Table 16.4  Patient-Specific Modifiers for the New AOSpine Subaxial Cervical Spine Injury Classification System Modifier

Definition

M1

Unclear integrity of the posterior ligamentous complex Significant disk herniation present The patient has a of a stiffening/ metabolic bone disease such as diffuse idiopathic skeletal hyperostosis or ankylosing spondylitis Vertebral artery injury

M2 M3

M4

175



176

Chapter 16 the effect of individual variables on the treatment algorithms, and eventually an AOSpine Subaxial Cervical Injury Score will be published as a treatment algorithm to accompany the new classification. In an effort to prevent the errors of the previous classification systems, the development of the surgical algorithm is

References

Five Must-Read References 1. Schatzker J, McBroom R, Bruce D. The tibial plateau fracture. The Toronto experience 1968–1975. Clin Orthop Relat Res 1979;138:94–104 2. Schatzker J. Compression in the surgical treatment of fractures of the tibia. Clin Orthop Relat Res 1974; 105:220–239 3. Bohler L. Die Technik der Knochenbruchbehandlung. Wien: Maudrich; 1951 4. Holdsworth F. Fractures, dislocations, and fracture-dislocations of the spine. J Bone Joint Surg Am 1970;52:1534–1551 5. Allen BL Jr, Ferguson RL, Lehmann TR, O’Brien RP. A  mechanistic classification of closed, indirect fractures and dislocations of the lower cervical spine. Spine (Phila Pa 1976) 1982;7:1–27  6. Stone AT, Bransford RJ, Lee MJ, et al. Reliability of classification systems for subaxial cervical injuries. Evid Based Spine Care J 2010;1:19–26

being done in a stepwise fashion using a modified Delphi method. In this way, global input will be used to determine the treatment algorithm, and a universally accepted treatment algorithm for subaxial cervical spine injuries will be established.

7. Harris JH Jr, Edeiken-Monroe B, Kopaniky DR. A practical classification of acute cervical spine injuries. Orthop Clin North Am 1986;17:15–30  8. Vaccaro AR, Hulbert RJ, Patel AA, et al. The subaxial cervical spine injury classification system: a novel approach to recognize the importance of morphology, neurology, and integrity of the disco-ligamentous complex. Spine (Phila Pa 1976) 2007;32:2365–2374  9. van Middendorp JJ, Audige L, Bartels RH, et al. The Subaxial Cervical Spine Injury Classification System: an external agreement validation study. Spine J 2013;13:1055–1063 10. Vaccaro AR, Koerner JD, Radcliff KE, et al. AOSpine subaxial cervical spine injury classification system. Eur Spine J. 2015 Feb 26 [Epub ahead of print] 11. Vaccaro AR, Oner C, Kepler CK, et al. AOSpine thoracolumbar spine injury classification system: fracture description, neurological status, and key modifiers. Spine (Phila Pa 1976). 2013;38:2028–2037

Index

Note: Page references followed by f or t indicate pages or tables, respectively. A Accessory nerve, 51 Agency for Healthcare Research and Quality (AHRQ), 94–95 Airway obstruction, closed reduction-related, 40 Alar ligaments, anatomy and function of, 18, 19, 50 Ankylosing spondylitis biomechanics of, 140–141 cervical spine trauma associated with, 102, 103, 139–146 prehospital assessment and transportation in, 142 treatment for, 142–144, 143f definition of, 102 diagnosis of, 140 epidemiology of, 140 evaluation of, 96 imaging of, 102, 140, 144–145 pathophysiology of, 139–140 Ankylosis, spinal, 139. See also Ankylosing ­spondylitis; Diffuse idiopathic skeletal hyperostosis (DISH) osteoporosis associated with, 140–141 Ansa cervicalis, 14 Anterior approach anatomic considerations in, 1 to compression fractures, 89–90 to facet joint dislocations, 121, 122–123, 125–126 to lateral mass fractures, 111 between neurovascular and visceral compartments, 14, 14f Anterior cervical diskectomy and fusion of facet joint dislocations, 121, 123 of facet joint fractures, 107f of flexion-distraction injuries, 100, 100f

Anterior fixation of flexion-distraction injuries, 101–102 in rheumatoid arthritis patients, 149 Anterior fusion, in children, 166 Anterior longitudinal ligament anatomy and function of, 3, 4f, 18–19 injuries to extension-distraction injury-related, 100 lateral mass fracture-related, 109 tears, 22 AO Spine Subaxial Cervical Spine Injury Classification System, 83–84, 84t, 115, 118, 119t, 169–176 compression injuries (type-A), 115, 118, 170, 170f, 171f subtypes of, 170f, 171f, 173t distraction/tension band injuries (type B), 115, 118, 119t, 170, 172f subtypes of, 170, 172f, 173t facet joint injuries, 119t, 174, 174f, 174t, 175f neurologic status evaluation, 174, 175t reliability analysis of, 175, 177 translational injuries (type C), 115, 118, 119t, 170, 173f subtypes of, 173f Ascending cervical artery, anatomy of, 6 Aspen rigid cervical orthosis, 41, 42, 42f Atlanto-axial complex, osteoporotic fractures of, 151 Atlanto-axial fusion, posterior, of atlas fractures, 65, 68–70, 68f, 69t Harms technique, 68, 69t, 70 Magerl/Gallie technique, 68, 69, 69t, 70 Atlanto-axial joints anatomy and function of, 9, 18 dislocation of, 23



178 Index Atlanto-axial joints (continued) injuries to, in children, 163 subluxation of, 23 rheumatoid arthritis-related, 147, 148, 150 rotatory, in children, 163, 164f Atlanto-axial junction, instability of, 19 Atlanto-dens interval (ADI) anterior, in rheumatoid arthritis, 148 in children, 159 definition of, 159 in spinal instability, 19 Atlanto-occipital dissociation (AOD) anatomic features and biomechanics of, 50–51 classification of, 53 delayed diagnosis of, 59 diagnosis of, 51–56 epidemiology of, 49–50 prognosis and outcome of, 58 treatment for, 56–58, 59 Atlanto-occipital joints anatomy and function of, 8–9, 15 in children, 158–159, 161 dislocations of, 156–157, 162–163 Atlanto-occipital membrane, anatomy and function of, 50 Atlas (C1), 77, 77f anatomy and function of, 4f, 7f, 8, 15, 17–18 anomalies of, 77 development of, 76–77, 158 ossification centers of, 158 Atlas body, fractures of, 79–80, 81 Atlas fractures avulsion-type, 22 burst, 61, 62 stable, 63 unstable, 63, 68 classification of, 61, 62, 62f, 63f clinical presentation of, 61–62 Dickman type, 63f, 65 Gehweiler type, 62, 62f, 63–65 imaging of, 63, 63f, 70 Jefferson, 61 in children, 57 halo vest immobilization of, 43 pseudo-Jefferson, 159 nonoperative treatment for, 45 operative management of, 65–70, 66f with isolated osteosynthesis, 65–68, 71 therapy algorithm for, 63–65, 64f with transverse atlantal ligament bony avulsion, 61, 62, 63f, 64, 66f, 71 unstable, 62, 63 conservative management of, 65 Axis (C2) anatomy and function of, 2f, 8, 15, 18 in children, 76–77 anomalies of, 77 development of, 76–77, 158 ossification centers of, 77, 77f, 158

Axis fractures, 22–23 hangman’s fractures, 22–23, 77–79 C1-C2 pedicle fixation of, 78 nonoperative treatment for, 43, 44, 78 B Babinski’s sign, 131 Basion-axial interval (BAI), 161 Basion-dens interval (BDI), 161 Biomechanics, of the cervical spine, 17–24 in children, 158–159 compressive forces, 19 functional anatomy and stability, 17–19, 19t of injured cervical spine, 20–23 extension injuries, 22–23 flexion injuries, 20–22 instability, 19–20 Blunt cervical trauma evaluation of, 25–38 grading of, 32 Blunt head trauma, 51 Braces for cervicothoracic junction injuries, 133 for compression fractures, 89 Minerva-type, 41–42, 43–44 Brain injury, atlanto-occipital dissociation-related, 51 “Burners”, 165 C C-spine clearance protocol, 30–32, 31f, 33f, 35 for children, 159–162, 167 C2. See Axis Cardiac arrest, craniocervical instability-related, 51 Cervical collars, 40–42, 41f, 42f for atlanto-occipital dissociation, 57 for cervical sprains, 44 complications of, 42 for compression fractures, 87 for craniocervical junction injuries, 56–57 for hangman’s fractures, 78 types of, 41–42 use in children, 160 Cervical cord neurapraxia, 165 Cervical immobilization in children, 159–160 discontinuation of, 25, 30–32, 35 Cervical spine anatomy and function of, 1–16 adult/child comparison of, 158–159 joints and ligaments, 3–4, 4f, 8–10, 15 muscles, 4–6, 7f, 11f, 12 occipital and upper spine, 6–12 subaxial spine, 12–15 suboccipital region, 10–12, 10t, 11f upper cervical spine, 17–18 vascular supply, 6 topographical relationships of, 13–15

Index Cervical spine injuries. See also specific types of injuries evaluation of, 25–38, 95–97 C-spine clearance protocol in, 30–32, 31f, 33f, 35 clinical evaluation, 25–26 magnetic resonance imaging in, 34 plain radiography versus CT scans in, 32–34 radiological assessment in, 26–30, 27f–30f nonoperative management of, 39–48 with cervical orthoses, 40–42, 41f, 42f general principles of, 44–46 with halo vest immobilization, 42–44 initial assessment in, 39 with skeletal traction, 39–40 Cervical Spine Injury Severity Score (CSISS), 84, 105 Cervical thoracic orthoses, 89 Cervicothoracic junction anatomy and function of, 130, 131f, 134, 136 injuries to, 130–138 closed reduction of, 133 diagnosis of, 130–133 fracture-dislocations, 130, 131f imaging of, 133, 137, 151 nonsurgical treatment for, 133 osteoporotic fractures, 148, 151, 153 surgical approaches to, 134–137, 134t, 135f, 136f treatment algorithm for, 133, 134f Children C2 anatomy in, 76–77 cervical spine injuries in, 156–168 anatomic considerations in, 158–159, 167 C2 fractures, 76–77, 81 cervical spine clearance protocol for, 159–162, 167 epidemiology of, 156–157 imaging of, 76–77, 160–162 mechanism of injury in, 157–158 outcomes and late complications of, 166–167 specific injuries, 162–166 treatment for, 166 Clay-shoveler’s fractures, 20 Closed reduction, of cervical spine, 39–40. See also under specific injuries Collet-Sicard syndrome, 61–62 Comatose patients/unconscious patients C-spine clearance protocol for, 32 cervical spine injury imaging in, 26, 28, 34, 35, 39 prior to closed reduction, 40 Compression fractures AO type-A, 83–93, 94, 170, 170f, 171f burst-type, 85–88, 86f–87f classification of, 83–84, 84t, 115, 118, 119t epidemiology of, 85 imaging of, 85–86, 86f–87f impaction-type, 84t, 85, 91 initial management of, 87–88 nonsurgical treatment for, 88, 89, 91–92 split-type, 84t, 85, 91

subtypes of, 170f, 171f, 173t surgical treatment for, 88, 89–92 flexion-compression (teardrop), 21, 157 osteoporotic odontoid process fractures, 151–153, 153f patterns of, 150–151 treatment for, 151–153 simple wedge, 21 Computed tomography (CT), of cervical spine injuries, 26, 29f, 34, 39 of atlanto-occipital dissociation, 52–53 in children, 160, 161–162 comparison with plain radiographs, 32–34 Condylar gap, 161 Condyle-C1 interval (CCI), 52–53, 53f Corticosteroids, as spinal cord injury treatment, 97 Costotransversectomy, 134t, 135f, 137 Cranial nerve palsy craniocervical trauma-related, 51 occipital condyle fracture-related, 59 Craniocervical dislocation. See Atlanto-occipital dissociation Craniocervical dissociation. See Atlanto-occipital dissociation Craniocervical junction, anatomy and function of, 50–51 Craniovertebral joints, anatomy and function of, 8, 15, 16 Craniovertebral junction, injuries to, 49 D Decompression, of traumatic cervical spine fractures, 39–40 Decubitus ulcers, cervical orthoses-related, 42 Deep cervical artery, anatomy of, 6 Dens. See Odontoid process Diffuse idiopathic skeletal hyperostosis (DISH), 22, 139–146 biomechanics of, 140–141 with C6-C7 extension-distraction injuries, 98f cervical spine fractures associated with, 102, 103, 139–146 diagnosis of, 140 epidemiology of, 140 imaging of, 140, 144–145 prehospital assessment and transportation for, 142 treatment for, 142–144 definition of, 102 evaluation of, 96 imaging of, 102 DISH. See Diffuse idiopathic skeletal hyperostosis (DISH) Disk disruption, in flexion-distraction injuries, 98–99 Disk herniation closed reduction-related, 99 facet joint dislocation-related, 120–121, 123–124, 125–126, 125f, 127

179



180 Index Disk space injuries, 22 Distraction injuries (AO type-B), 94–104 ankylosing spondylitis and, 94 classification of, 95, 96f, 96t, 115, 118, 119t, 170, 172f, 173f closed reduction of, 103 diffuse skeletal hyperostosis and, 94 extension-distraction, 94 extension-distraction injuries, 95 flexion-distraction, 94 hyperextension injuries, 95 imaging of, 97, 97f, 98f management of, 97 morphology of, 95 subtypes of, 170, 172f, 173f DLC, in compression injuries, 88, 89, 91 Dorsal approaches, to cervicothoracic junction injuries, 132f, 136–137 Dorsal muscles, anatomy and function of, 4, 7f, 15 Dual-energy X-ray absorptiometry (DEXA), 150 Dublin method, of atlanto-occipital dissociation diagnosis, 52 Dysphagia, 42, 51, 59 E Epidural space, 9, 10 Erector muscle, anatomy and function of, 5 Extension injuries, 22–23 Extension instability, 19 Extension-distraction injuries (EDIs), 94, 95, 100–102, 101f closed reduction of, 101 nonsurgical treatment for, 101 surgical approaches to, 101–102 F Facet joints anatomy and function of, 2f, 8, 12, 15, 18 dislocations of, 21, 22, 115–129 bilateral, 97f, 117f, 120, 123, 125f, 126 classification of, 115–118, 118t, 119t closed reduction of, 120–121, 124–125, 124f, 127 flexion-distraction, 97f, 99, 120 imaging of, 118–119, 120–121, 127 initial management of, 120–121 pathomechanics of, 119–120 subluxations, 120 surgical management of, 121–127, 122t, 124f unilateral, 115, 116f, 120, 123 fracture-dislocations of, 108, 108f, 120 fractures of, 21, 22 level of injury of, 108 mechanism of injury of, 106, 113 nonoperative treatment for, 44 soft tissue involvement in, 109, 113 spinal cord injury associated with, 110 treatment for, 111–113, 112–113 injury classification of, 174, 174f, 174t, 175f Fascia, cervical, 13–14, 14f

Flexion injuries biomechanics of, 20–22 subaxial, 97 Flexion instability, 19 Flexion-distraction injuries, 21, 94, 98–100 closed reduction of, 99 of the facet joints, 97f, 99, 120 imaging of, 97f, 98f nonsurgical treatment for, 99, 100, 101 surgical approaches to, 99–100 Flexion-rotation injuries, 21 Flexion-translation injuries, 21 Fractures. See also specific types of fractures closed reduction of, 39–40 gunshot wound-related, 44–45 G Gardner-Wells tongs, 39, 45, 87, 133 Glossopharyngeal nerve, 51 Grades of Recommendation, Assessment and Evaluation (GRADE) Working Group, 94–95 Greater occipital nerve, anatomy and function of, 10–11, 11f Gunshot wounds, 44–45 H Halo vest, 42–44 for atlas fractures, 65 for cervicothoracic junction injuries, 133 complications of, 44, 65, 89, 151–152 for compression fractures, 88, 89 for craniocervical junction injuries, 56–57 for dens (odontoid process) fractures, 44 for flexion-distraction injuries, 99, 100, 101 for hangman’s fractures, 78 for occipital condyle fractures, 59 use in children, 163, 166, 167 use in elderly patients, 151–152 use in rheumatoid arthritis patients, 149 Hangman’s fractures, 22–23, 77–79 C1-C2 pedicle fixation of, 78 nonoperative treatment for, 43, 44 Harris basion-axis interval, 52 Hyperextension injuries as neurologic injury cause, 101 spinal ankylosis-related, 141, 141f, 144 of the upper spine, 22 Hyperflexion injuries, in children, 157 Hypoglossal nerve lesions, 51 Hypoglossal nerve palsy, 57 Hypoglossal nerve, anatomy and function of, 51 I Iliocostalis muscle, anatomy and function of, 5, 5t Imaging, of cervical spine injuries, 25–38. See also Computed tomography (CT): Magnetic resonance imaging (MRI); X-rays in children, 160–162 in comatose/unconscious patients, 26, 28, 34, 35, 39, 160–162

Index Instability, definition of, 19–20 Instrumentation, cervical, use in children, 166 Interspinalis muscle, anatomy and function of, 5t, 6 Interspinous ligament, anatomy and function of, 3, 4f Intertransversarii muscle, anatomy and function of, 5t, 6 Intervertebral disks. See also Disk disruption; Disk herniation; Disk space injuries anatomy and function of, 12, 15 J Jefferson fractures. See Atlas fractures, Jefferson Journal of Bone and Joint Surgery, American Volume, 94 K Kyphosis cervicothoracic junction injury-related, 132f, 133, 136 osteoporosis-related, 150, 151 posttraumatic, in children, 166 L Lateral flexion injuries, in children, 157 Lateral mass fracture-separation, 22 Lateral mass fractures, 105–114 anatomic considerations in, 105–106 classification of, 106–108, 107t comminuted-type, 107, 111 definition of, 105 floating mass-type, 105, 107, 111, 112f level of injury of, 108 mechanism of injury of, 106 neurovascular injuries associated with, 109–110 pathoanatomy of, 108–109 soft tissue involvement in, 109, 113 split-type, 107, 111 treatment for, 111–112 Lateral mass screws, bicortical and unicortical, 79, 81 Latissimus dorsi muscle, anatomy and function of, 5 Lee’s X-line method, 52 Levator scapulae muscle, anatomy and function of, 5, 13 Ligament injuries to cervicothoracic junction, 137 in children, 161 as instability cause, 20 posterior, 20 Ligamenta flava, anatomy and function of, 3–4, 4f Ligaments anatomy and function of, 18 of craniocervical junction, 50 Longissimus muscle, anatomy and function of, 5, 5t Longus capitis muscle, anatomy and function of, 13 Longus colli muscle, anatomy and function of, 13 Lordosis, cervical, 17 absence of, in children, 159

Lower cervical injuries. See also Subaxial spine in children, 163 M Magnetic resonance imaging (MRI), of cervical spine injuries, 28, 30, 30f, 39 of atlanto-occipital dissociation, 53 in children, 160, 162, 165 for diskoligamentous complex integrity assessment, 170 for instability determination, 20, 23 prior to closed reduction, 40 Methylprednisone, use in children, 166 Miami-J rigid cervical collars, 41, 42f, 43 Midthoracic region, osteoporotic fractures of, 150, 153–154 Minerva brace, 41–42, 43–44 Multifidus muscle, anatomy and function of, 5t, 6 Muscles, of the back, 4–6, 7f, 11f, 12. See also specific muscles deep, 4, 5–6, 5t extrinsic, 4–5 intrinsic, 4–5, 5t Myelopathy, traumatic, 28, 30f in children, 158 N Neck, transverse sections of, 13–15, 14f Neonates, cervical spine injuries in, 165 Neurologic examination, 96 in rheumatoid arthritis patients, 149 Neurologic impairment cervicothoracic junction injury-related, 130–131, 133 in children, 156, 167 spinal ankylosis-related, 142, 144, 145 Neurologic status, grading of, 174, 175t Nuchal ligament, anatomy and function of, 3, 4f, 14f, 15, 50 O Obliquus capitis muscles, anatomy and function of, 10, 10t, 11f Occipital artery, anatomy of, 12 Occipital bone, anatomy of, 4f, 6–8, 7f Occipital condyles anatomy and function of, 8, 50–51 fractures of, 39, 44–45 anatomic features and biomechanics of, 50–51 avulsion fractures, 50, 54, 54f, 55f–56f classification of, 53–56, 54f–56f compression fractures, 54f epidemiology of, 50 incidence of, 50 prognosis and outcome of, 58 treatment for, 56–58 Occipitoatlantal joints anatomy and function of, 50 in rheumatoid arthritis, 148

181



182 Index Occipitocervical dissociation. See Atlanto-occipital dissociation (AOD) Occipitocervical fusion, 57–58, 59 of atlas fractures, 64 in children, 166 Occipitocervical joint, anatomy and function of, 18 Occipitocervical junction dislocation of, 22 instability of, 19 Odontoid process (dens) anatomy and function of, 2f, 8, 9, 10 ossification centers of, 158 Odontoid process (dens) fractures, 73–77 anterior screw fixation of, 73–74, 75, 76 in children, 157, 163 classification of, 73, 74f closed reduction of, 40 in elderly patients, 73, 74–76 nonsurgical treatment for, 40, 43, 45 osteoporotic, 151–153, 152f surgical versus nonsurgical treatment for, 74–76 Orthoses, cervical, 40–42, 41f, 42f complications of, 42, 89 for osteoporotic fractures, 152 types of, 41–42 use in rheumatoid arthritis patients, 149 Os odontoideum, 166 Ossification, diffuse idiopathic skeletal hyperostosis-­ related, 140 Osteoporosis as compression fracture cause, 147 odontoid process fractures, 147–148, 151–153, 153f patterns of, 150–151 treatment for, 151–153 pathophysiology of, 150 spinal ankylosis-related, 140–141 Osteosynthesis, of the atlas, 65–68, 67t P Pars interarticularis fractures. See also Hangman’s fractures; Spondylolysis in children, 165–166 Philadelphia cervical collars, 41, 42, 43 Phrenic nerve injuries, 157, 158 PMT® CervMax™ Cervical Orthosis Collar, 41 Posterior approach anatomic considerations in, 1 to compression fractures, 91 to facet joint dislocations, 121–123, 126 to flexion-distraction injuries, 99–100, 101f to lateral mass fractures, 111 Posterior fixation of flexion-distraction injuries, 101–102 in rheumatoid arthritis patients, 149 Posterior fusion, in children, 166 Posterior ligamentous complex, disruption of, 97, 98f

Posterior longitudinal ligament anatomy and function of, 3, 4f, 18–19 injuries to facet joint fracture-related, 109 flexion-distraction injuries-related, 98–99 transection, 20 Powers ratio, 52 in children, 161, 163 Predental space, in children, 161 Prevertebral muscles, anatomy and function of, 4 Prevertebral space, in children, 159 Pseudoarthroses, in children, 159 Pseudosubluxation, in children, 159 R Radiculopathy, facet joint fracture-related, 110 Rectus muscles, anatomy and function of, 10, 10t, 11f, 12, 13 Recurrent laryngeal nerve, anatomy and function of, 15 Retropharyngeal space, in children, 159, 161 Retrotracheal space, in children, 161 Rheumatoid arthritis, 147, 148–150, 153 cervical spine trauma in evaluation of, 149 imaging of, 149 treatment for, 149–150, 153, 154 pathophysiology and biomechanics of, 148–149, 148f spinal instability in, 147 Rhomboid muscles, anatomy and function of, 5 Rotation injuries, 94 in children, 157 Rotation, of cervical spine, 19, 19t Rotatores muscle, anatomy and function of, 5t, 6 “Rule of Spence,” 63 S Sacroiliitis, 140 Scalenus muscles, anatomy and function of, 13 SCIWORA (spinal cord injury without radiographic abnormality), 158, 162, 165 Seatbelt injuries, in children, 157 Semispinalis capitis muscle, anatomy and function of, 10, 11f Skull base, fractures of, 54, 54f Smith-Robinson anteromedial approach, 136 Space available for the cord (SAC), 19 in rheumatoid arthritis, 149, 150 Spinal cord concussion, 165 Spinal cord injury atlanto-occipital dissociation-related, 51 burst fracture-related, 85 cervicothoracic junction injury-related, 131 in children, 157–158, 167 facet joint fracture-related, 110 without radiographic abnormality (SCIWORA), 158, 162, 165

Index Spinal cord, anatomy and function of, 9–10 Spinal shock, 96–97, 158 Spinous processes anatomy and function of, 2f, 3, 8, 14f avulsion of, 20 Splenius capitis muscle, anatomy and function of, 5, 5t, 6 Splenius cervicis muscle, anatomy and function of, 5, 5t, 6 Spondylolisthesis degenerative, differentiated from subaxial subluxation, 148–149 traumatic cervical. See Hangman’s fractures Spondylolysis lateral mass injury as, 107, 108, 111 unilateral, 109 Sports-related injuries, 165 Sprains, cervical, 44 Stability, definition of, 19 Stenosis, congenital cervical, 22 “Stingers,” 165 Subaxial cervical spine anatomy and function of, 12–15, 18–19 development of, 158 dislocations of, 39 fractures of, 39 nonoperative treatment for, 44 instability of, 19–20 Subaxial Cervical Spine Injury Classification (SLIC) and Severity Scale, 84, 88, 95, 96t, 115, 118t, 133 limitations of, 169–170 Subaxial stabilization, in children, 166 Suboccipital muscles, anatomy and function of, 6, 10, 10t Suboccipital nerve, anatomy and function of, 11–12, 11f Suboccipital region, anatomy and function of, 10–12, 10t, 11f Suboccipital triangle, anatomy and function of, 10, 11f Sun’s interspinous ratio, 52 Supraspinous ligament, anatomy and function of, 3, 4f Swischuk’s line, 59, 161 Sympathetic trunk, 14, 15 Synchondroses, 156 differentiated from C2 fractures, 165–166 misinterpreted as fractures, 159 T Teardrop fractures, 21 in children, 157 Tectorial membrane, anatomy and function of, 9, 50 Tension band injuries (AO-type B), 170, 172f subtypes of, 170, 172f, 173t Third occipital nerve, anatomy and function of, 11, 11f

Thoracolumbar junction, osteoporotic fractures of, 150–151, 153–154 Thoracolumbar spine injuries, classification of, 83–84, 169 Torticollis, craniocervical trauma-related, 51 Traction, 39–40 for cervicothoracic junction injuries, 133 for compression fractures, 87, 88 for facet joint dislocations, 120 for hangman’s fractures, 78–79 Transarticular screw osteosynthesis, of C0-C1, 57 Translational injuries (AO type-C), 170, 173f classification of, 115, 118, 119t subtypes of, 173f Transverse atlantal ligament, bony avulsion of, 61, 62, 63f, 64, 66f, 71 Transverse ligament, anatomy and function of, 9 Transverse process, anatomy and function of, 2f, 3, 8 Transversospinalis muscles, anatomy and function of, 5–6, 5t, 5t Trapezius muscle, anatomy and function of, 5, 6, 7f Traumatic brain injury, occipital condyle fracture-­ associated, 50 U Uncinate process anatomy and function of, 18 fractures of, 21 Unconscious patients. See Comatose/unconscious patients Uncovertebral joints, anatomy and function of, 12 Upper cervical spine, fractures of, 39 nonoperative treatment for, 44–45 V Vagal nerve, 51 Venous plexuses anatomy and function of, 6, 10 suboccipital, 12 Ventral approaches, to cervicothoracic junction injuries, 134, 136, 136f Vertebrae, cervical. See also Atlas (C1); Axis (C2) anatomy and function of, 1–3, 2f ossification centers in, 158 Vertebral arch, cervical, anatomy and function of, 1, 2f Vertebral artery injuries atlas fracture-related, 63, 67, 97 axis fracture-related, 97 in children, 157 diagnosis of, 127 facet joint dislocation-related, 127–128 facet joint fracture-related, 110–111 flexion-distraction injuries-related, 99 lateral mass fracture-related, 109–110 risk factors for, 127 treatment for, 127

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184 Index Vertebral artery, anatomy of, 6, 8, 10, 11–12, 11f, 14f, 15 Vertebral bodies, cervical anatomy and function of, 1, 2f fractures of, 98f osteoporotic compression fractures of, 148 wedging of, in children, 159 Vertebral foramen, anatomy and function of, 1, 2f, 3 Vertebral notch, anatomy and function of, 2f, 3 Vista cervical collars, 41

W Whiplash injuries, treatment for, 44 Wholey basion-dens interval, 52, 52f X X-rays, of cervical spine injuries, 26, 27f, 28f of atlanto-occipital dissociation, 52, 53 comparison with computed tomography, 32–34 of craniocervical junction injuries, 59 of pediatric cervical spine trauma, 161–162