Ultrasound of the Musculoskeletal System (Medical Radiology) [2007 ed.] 9788181287038, 3540422676

Table of contents :
Cover
Ultrasoundof theMusculoskeletalSystem
Series Editor’s Foreword
Foreword
Preface
Contents
Instrumentation
1 Technical Requirements
1.1 Advances in US Technology
1.1.1 Transducers
1.1.2 Imaging Algorithms
1.1.3 Ultrasound Contrast Media
References
General
2 Skin and Subcutaneous Tissue
2.1 Histologic Considerations
2.2 Normal US Findings
2.3 Pathologic Findings
2.3.1 Skin Abnormalities
2.3.2 Subcutaneous Tissue Abnormalities
2.3.3 Tumors and Tumor-Like Conditions
References
3 Muscle and Tendon
3.1 Muscle
3.1.1 Histologic Considerations
3.1.2 Normal US Anatomy and Scanning Technique
3.1.3 Anatomical Variants and Heritable Disorders
3.1.4 Traumatic Lesions
3.1.5 Infl ammatory and Ischemic Conditions
3.1.6 Tumors
3.2 Tendon
3.2.1 Histologic Considerations
3.2.2 Normal US Anatomy and Scanning Technique
3.2.3 Tendon Instability
3.2.4 Degenerative Changes and Tendon Tears
3.2.5 Infl ammatory Conditions
3.2.6 Tumors and Tumor-Like Conditions
References
4 Nerve and Blood Vessels
4.1 Nerve
4.1.1 Histologic Considerations
4.1.2 Normal US Anatomy and Scanning Technique
4.1.3 Anatomic Variants, Inherited andDevelopmental Anomalies
4.1.4 Nerve Instability
4.1.5 Compressive Syndromes
4.1.6 Traumatic Injuries
4.1.7 Rheumatologic and Infectious Disorders
4.1.8 Tumors and Tumor-Like Conditions
4.2 Blood Vessels
4.2.1 Histologic Considerations
4.2.2 Normal US Anatomy and Scanning Technique
4.2.3 Musculoskeletal-Related Vascular Disorders
4.2.4 Vascular Tumors
References
5 Bone and Joint
5.1 Bone
5.1.1 Histologic Considerations
5.1.2 Normal US Anatomy and Scanning Technique
5.1.3 Outgrowths
5.1.4 Defects
5.1.5 Irregularities of the Cortical Outline
5.1.6 Osteomyelitis
5.2 Joint
5.2.1 Histologic Considerations
5.2.2 Normal US Anatomy and Scanning Technique
5.2.3 Pathologic Changes
5.3 Space-Occupying Masses
5.3.1 Bone Tumors
5.3.2 Pigmented Villonodular Synovitis
5.3.3 Lipoma Arborescens
5.3.4 Synovial Osteochondromatosis
5.3.5 Synovial Hemangioma
References
Individual Anatomic Sites
6 Shoulder
6.1 Introduction
6.2 Clinical Anatomy
6.2.1 Osseous and Articular Anatomy
6.2.2 Muscles and Tendons
6.2.3 Bursae and Gliding Spaces
6.2.4 Neurovascular Structures
6.2.5 Thoracic Outlet Structures
6.3 Essentials of Clinical History and PhysicalExamination
6.3.1 Rotator Cuff Pathology
6.3.2 Thoracic Outlet and Brachial Plexus Pathology
6.4 Normal Ultrasound Findings and ScanningTechnique
6.4.1 Biceps Tendon and Rotator Cuff
6.4.2 Shoulder Beyond the Cuff
6.5 Shoulder Pathology
6.5.1 Pathophysiologic Overview
6.5.2 Rotator Cuff Pathology
6.5.3 Biceps Tendon Pathology
6.5.4 Shoulder Pathology Beyond the Rotator Cuff
6.5.5 Thoracic Outlet and Brachial Plexus Pathology
6.5.6 Shoulder Masses
References
7 Arm
7.1 Introduction
7.2 Clinical and US Anatomy
7.2.1 Anterior Arm
7.2.2 Posterior Arm
7.2.3 Neurovascular Bundle
7.3 Arm Pathology
7.3.1 Anterior Arm
7.3.2 Posterior Arm
References
8 Elbow
8.1 Introduction
8.2 Clinical Anatomy
8.2.1 Joint and Ligament Complexes
8.2.2 Muscles and Tendons
8.2.3 Neurovascular Structures
8.3 Essentials of Clinical History and Physical Examination
8.4 Ultrasound Anatomy and ScanningTechnique
8.4.1 Anterior Elbow
8.4.2 Medial Elbow
8.4.3 Lateral Elbow
8.4.4 Posterior Elbow
8.5 Elbow Pathology
8.5.1 Anterior Elbow Pathology
8.5.2 Medial Elbow Pathology
8.5.3 Lateral Elbow Pathology
8.5.4 Posterior Elbow Pathology
8.5.5 Bone and Joint Disorders
8.5.6 Elbow Masses
References
9 Forearm
9.1 Introduction
9.2 Clinical and US Anatomy
9.2.1 Volar Forearm
9.2.2 Dorsal Forearm
9.3 Forearm Pathology
9.3.1 Volar Forearm
9.3.2 Dorsal Forearm and Mobile Wad
References
10 Wrist
10.1 Introduction
10.2 Clinical Anatomy
10.2.1 Osseous and Articular Anatomy
10.2.2 Tendons and Retinacula
10.2.3 Neurovascular Structures
10.3 Essentials of Clinical History and PhysicalExamination
10.3.1 De Quervain Disease
10.3.2 Carpal Tunnel Syndrome
10.4 US Scanning Technique andNormal US Anatomy
10.4.1 Dorsal Wrist
10.4.2 Volar Wrist
10.5 Wrist Pathology
10.5.1 Dorsal Wrist Pathology
10.5.2 Ventral Wrist Pathology
10.5.3 Bone and Joint Disorders
References
11 Hand
11.1 Introduction
11.2 Clinical Anatomy
11.2.1 Osseous and Articular Anatomy
11.2.2 Tendons, Pulley System and Muscles
11.2.3 Neurovascular Structures
11.3 Essentials of Clinical History andPhysical Examination
11.3.1 Tendon Tears
11.4 US Scanning Technique and Normal USAnatomy
11.4.1 Hand
11.4.2 Fingers
11.5 Hand and Finger Pathology
11.5.1 Dorsal Hand and Finger Pathology
11.5.2 Palmar Hand and Finger Pathology
11.5.3 Foreign Bodies
11.5.4 Bone and Joint Disorders
11.5.5 Hand and Finger Masses
References
Individual Anatomic Sites
12 Hip
12.1 Introduction
12.2 Clinical Anatomy
12.2.1 Osseous and Articular Anatomy
12.2.2 Joint and Ligament Complexes
12.2.3 Muscles and Tendons
12.2.4 Neurovascular Structures
12.2.5 Bursae
12.3 Essentials of Clinical History and PhysicalExamination
12.4 Normal US Findings and ScanningTechnique
12.4.1 Anterior Hip
12.4.2 Medial Hip
12.4.3 Lateral Hip
12.4.4 Posterior Hip
12.5 Hip Pathology
12.5.1 Anterior and Medial Hip Pathology
12.5.2 Lateral Hip Pathology
12.5.3 Posterior Hip Pathology
12.5.4 Joint and Bone Disorders
12.5.5 Hip Masses
References
13 Thigh
13.1 Introduction
13.2 Clinical and US Anatomy
13.2.1 Anterior Thigh
13.2.2 Medial Thigh
13.2.3 Posterior Thigh
13.3 Thigh Pathology
13.3.1 Anterior Thigh
13.3.2 Medial Thigh
13.3.3 Posterior Thigh
13.3.4 Thigh Masses
References
14 Knee
14.1 Introduction
14.2 Clinical Anatomy
14.2.1 Osseous and Articular Anatomy
14.2.2 Joint and Ligamentous Complexes
14.2.3 Tendons
14.2.4 Popliteal Fossa
14.2.5 Bursae
14.3 Essentials of Clinical History and PhysicalExamination
14.3.1 Knee Joint Effusions
14.4 Normal US Findings and ScanningTechnique
14.4.1Anterior Knee
14.4.2 Medial Knee
14.4.3 Lateral Knee
14.4.4 Posterior Knee
14.5 Knee Pathology
14.5.1 Anterior Knee Pathology
14.5.2 Medial Knee Pathology
14.5.3 Lateral Knee Pathology
14.5.4 Posterior Knee Pathology
14.5.5 Joint and Bone Disorders
14.5.6 Knee Masses
References
15 Leg
15.1 Introduction
15.2 Clinical and US Anatomy
15.2.1 Anterolateral Leg
15.2.2 Posteromedial Leg
15.3 Leg Pathology
15.3.1 Anterolateral Leg
15.3.2 Posteromedial Leg
15.3.3 Leg Masses
References
16 Ankle
16.1 Introduction
16.2 Clinical Anatomy
16.2.1 Joints and Ligament Complexes
16.2.2 Tendons and Retinacula
16.2.3 Neurovascular Structures
16.3 Essentials of Clinical History and PhysicalExamination
16.3.1 Ankle Sprains
16.3.2 Achilles Tendon Tears
16.4 Normal US Findings and ScanningTechnique
16.4.1 Anterior Ankle
16.4.2 Lateral Ankle
16.4.3 Medial Ankle
16.4.4 Posterior Ankle
16.5 Ankle Pathology
16.5.1 Anterior Ankle Pathology
16.5.2 Lateral Ankle Pathology
16.5.3 Medial Ankle Pathology
16.5.4 Posterior Ankle Pathology
16.5.5 Bone and Joint Disorders
16.5.6 Ankle Masses
References
17 Foot
17.1 Introduction
17.2 Clinical Anatomy
17.2.1 Osseous and Articular Anatomy
17.2.2 Soft Tissues: Dorsal Foot
17.2.3 Soft Tissues: Plantar Foot
17.2.4 Joints and Para-articular Structures of the Toes
17.3 Essentials of Clinical History and PhysicalExamination
17.3.1 Morton Neuroma and Metatarsalgia
17.4 US Scanning Technique and Normal USAnatomy
17.4.1 Dorsal Foot
17.4.2 Plantar Foot
17.5 Foot Pathology
17.5.1 Dorsal Hindfoot and Midfoot
17.5.2 Plantar Hindfoot and Midfoot
17.5.3 Forefoot
17.5.4 Foot Masses
References
Interventional Procedures
18 US-Guided Interventional Procedures
18.1 General Considerations
18.1.1 US-guided Needle Placement
18.1.2 Arthrocentesis and Drainage of Soft-TissueCollections
18.1.3 Steroid Injection Procedures
18.1.4 Tumor Biopsy
18.1.5 Removal of Foreign Bodies
18.1.6 US-Guided Regional Anesthesia
18.1.7 Treatment of Painful Neuromas
18.2 Specifi c Applications
18.2.1 Shoulder
18.2.2 Elbow
18.2.3 Wrist and Hand
18.2.4 Adult Hip
18.2.5 Knee
18.2.6 Ankle and Hindfoot
18.2.7 Forefoot
References
Pediatric Applications
19 Pediatric Musculoskeletal Ultrasound
19.1 Introduction
19.2 Hip Disorders
19.2.1 Developmental Dysplasia of the Hip
19.2.2 Painful Hip
19.3 Disorders Beyond the Hip
19.3.1 Bone
19.3.2 Tendons and Ligaments
19.3.3 Joints
19.3.4 Muscles
References
Subject Index
List of Contributors

Citation preview

Contents

MEDICAL RADIOLOGY

Diagnostic Imaging Editors: A. L. Baert, Leuven M. Knauth, Göttingen K. Sartor, Heidelberg

I

Contents

Stefano Bianchi · Carlo Martinoli

Ultrasound of the Musculoskeletal System With Contributions by

L. E. Derchi · G. Rizzatto · M. Valle · M. P. Zamorani Foreword by

A. L. Baert

Introduction by

I. F. Abdelwahab

With 1111 Figures in 3669 Separate Illustrations, 286 in Color

123

III

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Contents

Stefano Bianchi, MD Privat-docent Université de Genève Consultant Radiologist Fondation et Clinique des Grangettes 7, ch. des Grangettes 1224 Genève Switzerland Carlo Martinoli, MD Associate Professor of Radiology Cattedra “R” di Radiologia - DICMI Università di Genova Largo Rosanna Benzi, 8 16132 Genova Italy

Medical Radiology · Diagnostic Imaging and Radiation Oncology Series Editors: A. L. Baert · L. W. Brady · H.-P. Heilmann · M. Knauth · M. Molls · C. Nieder · K. Sartor Continuation of Handbuch der medizinischen Radiologie Encyclopedia of Medical Radiology

Library of Congress Control Number: 2003057335

ISBN 978-3-540-42267-9 Springer Berlin Heidelberg New York This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitations, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable for prosecution under the German Copyright Law. Springer is part of Springer Science+Business Media http//www.springer.com ¤ Springer-Verlag Berlin Heidelberg 2007 Printed in Germany The use of general descriptive names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Product liability: The publishers cannot guarantee the accuracy of any information about dosage and application contained in this book. In every case the user must check such information by consulting the relevant literature. Medical Editor: Dr. Ute Heilmann, Heidelberg Desk Editor: Ursula N. Davis, Heidelberg Production Editor: Kurt Teichmann, Mauer Cover-Design and Typesetting: Verlagsservice Teichmann, Mauer Printed on acid-free paper – 21/3151xq – 5 4 3 2 1 0

Contents

D e dicat ion

To Maria Pia, Elena and Eugenio, the loves of my life – S.B. To Maura and Roberto, for their love, support and forbearance – C.M.

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Contents

Series Editor’s Foreword

Modern ultrasound has now acquired a very important role in the spectrum of imaging modalities available for the study of the musculoskeletal system. This technique has become an indispensable tool in the clinical management of sports injuries, degenerative and traumatic lesions of the articulations and periarticular soft tissues, as well as – in certain circumstances – clinical management of the bones. Stefano Bianchi and Carlo Martinoli are internationally renowned leaders in their field who, as a long-standing and remarkable team, have acquired an exceptional expertise. This is amply demonstrated by their numerous and outstanding contributions to the literature, as well as by their worldwide lecturing and participation in teaching seminars on musculoskeletal ultrasound. Although some additional chapters have been authored by other well-known ultrasound specialists, most of the chapters have been prepared and written by Stefano Bianchi and Carlo Martinoli. This feature is a guarantee for uniformity and homogeneity of style, concept and presentation throughout the whole volume. An update of our knowledge and the latest insights into this subject are provided for each anatomic area of the musculoskeletal system. I would like to congratulate the authors most sincerely for their superb efforts in preparing this remarkable volume, which comprehensively covers the extensive and varied spectrum of musculoskeletal diseases, in the management of which ultrasound can make an important, if not essential, contribution to better clinical diagnosis and better guidance of therapy. Moreover, this work is superbly and abundantly illustrated by numerous anatomical drawings, photographs and ultrasound images, all realized with state-of-the-art and high-end equipment. These well chosen illustrations strongly enhance the didactic and educational value of this book. Without doubt, this outstanding volume will be of great value to certified general and musculoskeletal radiologists, radiologists in training, as well as orthopedic surgeons and rheumatologists in their daily clinical practice. I am confident that it will meet with the same success among readers as the previous volumes published in this series. Leuven

Albert L. Baert

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Contents

Foreword

Over the last 15 years, musculoskeletal ultrasonography has become an important imaging modality used in sports medicine, joint disorders, and rheumatology. With the rapid development and sophistication of this modality, essential information for a better understanding of the pathophysiologic assessment of many disorders has been established. This, in turn, has aided both in making crucial decisions regarding surgical intervention and in monitoring the effects of therapy. Equally important is the ready availability, affordability, speed, and diagnostic accuracy of ultrasonography. Ultrasound of the Musculoskeletal System is an invaluable text comprising 19 chapters and approximately one thousand pages and figures. The authors have designed unique schematic drawings which aid in better understanding the anatomy of the body part in terms of its sonographic characteristics discussed in each chapter. Correlations of ultrasonography with CT and MRI findings are applied throughout the text, demonstrating not only the exact indications for its use, but also highlighting its limitations. Technical advances continue to improve the utility of ultrasonography as a diagnostic technique in musculoskeletal imaging. Drs. Bianchi and Martinoli have successfully capitalized on the collaboration between radiologists, orthopedists, and rheumatologists as exemplified by their representative images and correlative discussions. Many of the techniques described in the text have been pioneered or improved by Dr. Bianchi and Dr. Martinoli. This text should become a key library reference source for radiologists, orthopedists, and rheumatologists. It is extremely readable and its illustrations help in the clarification of points made in the text. Ultrasound of the Musculoskeletal System is the most comprehensive work of its kind to date. It establishes a higher standard in musculoskeletal imaging and should remain a classic for years to come. Ibrahim Fikry Abdelwahab, MD Formerly Professor of Radiology The Mount Sinai School of Medicine, Weill Medical College, Cornell University, and New York Medical College

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Preface

The use of ultrasound in the assessment of the musculoskeletal system started many years ago. Nevertheless, the continuing innovations in instrumentation and the advances in clinical applications suggest that we have only just started to “peel the onion” in this field. This fact has also been reflected in the length of time needed to prepare this book. The project started some five years ago, with an approximate estimation of 300 pages to cover the whole field. As our personal experience and the literature expanded as a result of new technological improvements, more and more information was added, resulting in a final book size of over 1000 pages. This textbook can be considered the result of a continuing cooperation of two friends and colleagues who started their common practice many years ago publishing scientific papers and teaching at courses and congresses, and then decided to put their experience into a monograph with the aim of sharing their own knowledge and, most importantly, their enthusiasm for this wonderful imaging technique. Given these considerations, this book aims to cover the whole of this field, thus providing both help to those who are already expert in ultrasound and want to acquire further knowledge and skills in this special area, as well as an introduction to beginners, irrespective of whether they are musculoskeletal radiologists, rheumatologists, orthopaedic surgeons, or in-training residents, among others. Since many of the difficulties encountered while learning musculoskeletal ultrasound result from an inability to correctly interpret the images, many figure captions, references for probe placement, oneto-one correlations with clinical photographs, anatomical and operative specimens, as well as images obtained with other modalities were systematically added to the ultrasound illustrations. Schematic drawings have also been extensively used throughout the chapters to emphasize depiction of anatomy, pathomechanisms and biomechanics underlying the disease processes. It was our deliberate intention to compile the book with a uniform style throughout. This is the reason why most of the chapters have been written by the two editors and by a relatively small numbers of authors who have worked or continue to work with the editors. The book begins with an introductory section on the instrumentation and general aspects of musculoskeletal ultrasound, followed by a systematic overview of the applications of this technique in the different areas of the upper and lower extremities. An additional final section devoted to both interventional and pediatric applications has been included. With regard to certain clinical applications, there is still considerable difference of opinion on the role of musculoskeletal ultrasound as compared to that of other imaging modalities, such as magnetic resonance imaging. Obviously, there is a “bias” towards the use of ultrasound in this text. However, every effort has been made to provide accurate accounts of present knowledge and experience, as well as to indicate the most advanced references of emerging applications.

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A new textbook of this size inevitably contains errors and weaknesses -- we welcome corrections and suggestions for future editions. Meanwhile, happy reading! “Nulla res me delectabit, licet sit eximia et salutaris, quam mihi uni sciturus sum”. (Seneca, Epist. 6,4) “I might not be delighted with anything, even eminent and beneficial, if I am the only one to know it”. (Seneca, Epist. 6,4) Genève Genova

Stefano Bianchi Carlo Martinoli

Acknowledgments We are deeply indebted to the many colleagues who have provided information and illustrations of rare pathology, operative and anatomical views, as well as to the models who helped us to obtain correlative photos of anatomical landmarks. These colleagues are listed below. Special thanks go to Alberto Tagliafico (Genova, Italy) for the task of checking the entire book for errors, to the „Subject Index team“, including Enrico Capaccio, Maria Beatrice Damasio, Nunzia Pignataro, Nicola Stagnaro, Alberto Tagliafico and Simona Tosto, and to Jane Farrell for copyediting the manuscript and correcting language errors. Finally, it is a pleasure to acknowledge the skillful help, pleasant cooperation, and patience of the publisher’s staff during the five years of intense work it has taken to prepare this textbook. Elena and Eugenio Bianchi (Geneva, Switzerland) Silvio Boero (Genova, Italy) Gianni Cicio (Genova, Italy) Giovanni Crespi (Genova, Italy) Marino Delmi (Geneva, Switzerland) Jean H Fasel (Geneva, Switzerland) Sergio Gennaro (Genova, Italy) Maurizio Giunchedi (Lavagna, Italy) Claudio Guido Mazzola (Genova, Italy) Vincenzo Migaleddu (Sassari, Italy) Roberto Pesce (Genova, Italy) Nicolò Prato (Genova, Italy) Fabio Pretolesi (Genova, Italy) Maurizio Rubino (Genova, Italy) Federico Santolini (Genova, Italy) Giovanni Serafini (Pietra Ligure, Italy) Stefano Simonetti (Genova, Italy) Enrico Talenti (Padova, Italy) Paolo Tomà (Genova, Italy) Bruno Valle (Rapallo, Italy) Marzia Venturini (Genova, Italy) The Staff of the Institut de Radiologie, Clinique des Grangettes, (Geneva, Switzerland) and the Cattedra di Radiologia “R” – DICMI, Università di Genova (Genova, Italy).

Contents

Contents

Intrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

1 Technical Requirements Lorenzo E. Derchi and Giorgio Rizzatto . . . . . . . . . . . . . . . . . . . . . . .

3

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2 Skin and Subcutaneous Tissue Maura Valle and Maria Pia Zamorani. . . . . . . . . . . . . . . . . . . . . . . . . 19 3 Muscle and Tendon Maura Valle and Maria Pia Zamorani. . . . . . . . . . . . . . . . . . . . . . . . . 45 4 Nerve and Blood Vessels Maura Valle and Maria Pia Zamorani. . . . . . . . . . . . . . . . . . . . . . . . . 97 5 Bone and Joint Maura Valle and Maria Pia Zamorani. . . . . . . . . . . . . . . . . . . . . . . . . 137

Individual Anatomic Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 Upper Limb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 6 Shoulder Stefano Bianchi and Carlo Martinoli . . . . . . . . . . . . . . . . . . . . . . . . 189 7 Arm Carlo Martinoli and Stefano Bianchi . . . . . . . . . . . . . . . . . . . . . . . . 333 8 Elbow Stefano Bianchi and Carlo Martinoli . . . . . . . . . . . . . . . . . . . . . . . . 349 9 Forearm Carlo Martinoli and Stefano Bianchi . . . . . . . . . . . . . . . . . . . . . . . . 409 10 Wrist Stefano Bianchi and Carlo Martinoli . . . . . . . . . . . . . . . . . . . . . . . . 425 11 Hand Carlo Martinoli and Stefano Bianchi . . . . . . . . . . . . . . . . . . . . . . . . 495

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Lower Limb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 549 12 Hip Carlo Martinoli and Stefano Bianchi . . . . . . . . . . . . . . . . . . . . . . . . 551 13 Thigh Stefano Bianchi and Carlo Martinoli) . . . . . . . . . . . . . . . . . . . . . . . . 611 14 Knee Carlo Martinoli and Stefano Bianchi) . . . . . . . . . . . . . . . . . . . . . . . . 637 15 Leg Stefano Bianchi and Carlo Martinoli) . . . . . . . . . . . . . . . . . . . . . . . . 745 16 Ankle Carlo Martinoli and Stefano Bianchi) . . . . . . . . . . . . . . . . . . . . . . . . 773 17 Foot Stefano Bianchi and Carlo Martinoli) . . . . . . . . . . . . . . . . . . . . . . . . 835

Interventional Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 889 18 US-Guided Interventional Procedures Stefano BianchI and Maria Pia Zamorani . . . . . . . . . . . . . . . . . . . . . . 891

Pediatric Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 919 19 Pediatric Musculoskeletal Ultrasound Carlo Martinoli and Maura Valle . . . . . . . . . . . . . . . . . . . . . . . . . . . 921

Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 961 List of Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 975

Technical Requirements

Instrumentation

1

Technical Requirements

Technical Requirements Lorenzo E. Derchi and Giorgio Rizzatto

1.1.1 Transducers

CONTENTS 1.1 1.1.1 1.1.1.1 1.1.1.2 1.1.1.3 1.1.2 1.1.2.1 1.1.2.2 1.1.2.3 1.1.2.4 1.1.2.5 1.1.2.6 1.1.3

Advances in US Technology 3 Transducers 3 Broadband Transducers 3 Focusing 6 Transducer Selection and Handling 6 Imaging Algorithms 7 Advances in Doppler Imaging 8 Compound Imaging 8 Extended Field-of-View Imaging 9 Steering-Based Imaging 11 Three-Dimensional Imaging 13 Elastographic Imaging 14 Ultrasound Contrast Media 14 References

15

1.1 Advances in US Technology US technology is rapidly advancing and being refined, and is aimed at both increasing image quality and opening new fields of applications. This chapter will review the main advances in US technology and address the clinical impact they have had or are likely to have in the future in the field of the musculoskeletal system. New developments in transducer technology and advances in the quality and presentation of US images will be discussed.

L. E. Derchi, MD Professor of Radiology, Cattedra di Radiologia “R” - DICMI – Università di Genova, Largo Rosanna Benzi 8, 16132 Genova, Italy G. Rizzatto, MD Head of Department of Radiology, Ospedale di Gorizia, 34170 Gorizia, Italy

The transducer is an essential element of US equipment, responsible for the generation of a US beam and the detection of returning echoes. It greatly influences spatial resolution, penetration and signal-to-noise ratio. In recent years, research in transducer technology has been focused on the development of piezoelectric crystals with lower acoustic impedances and greater electromechanical coupling coefficients, as well as on improving the characteristics of absorbing backing layers and quarter-wave impedance matching layers (Claudon et al. 2002). Currently, transducer arrays formed by ceramic polymer composite elements of variable shape and thickness and multilayered technology are used, leading to a more accurate shaping of US pulses in terms of frequency, amplitude, phase and length (Whittingham 1999a; Rizzatto 1999). These refinements led to the use of very short pulses and an increased bandwidth (Fig. 1.1).

1.1.1.1 Broadband Transducers

One of the original objectives in designing broadband transducers was to improve axial resolution without changing the emission frequency. This is related to the fact that the shorter transmission pulses used in a broadband emission generate shorter echo pulses which can be faithfully converted into electric signals (Whittingham 1999b). Because short pulses suffer attenuation to a greater extent and are characterized by less penetration than long pulses, some specific techniques have been introduced by different manufacturers to compensate for these drawbacks, including single-pulse and multi-pulse techniques (Claudon et al. 2002). Among single-pulse techniques, the emission of a long, peculiarly shaped transmission pulse, which varies in frequency and

S. Bianchi, C. Martinoli, Ultrasound of the Musculoskeletal System, DOI 10.1007/978-3-540-28163-4_1, © Springer-Verlag Berlin Heidelberg 2007

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L. E. Derchi and G. Rizzatto

a

c

b

d

Fig. 1.1a–d. Relationship between spatial pulse length and frequency spectrum. a,b Intensity versus time diagrams illustrate different pulse lengths (λ). Two sine wave pulses are shown lasting 2 µs (four-cycle) and 1 µs (two-cycle) respectively. c,d Corresponding Fourier power (intensity versus frequency) diagrams show the spectrum of frequencies present in the pulses shown in a and b. The bandwidth is measured between the 6 dB points on each side of the spectrum. The longer pulse in a generates a narrower bandwidth (1 MHz) than the shorter pulse (2 MHz) in b

amplitude within the duration of the pulse itself, has been used instead of a simple sinusoidal pulse (Fig. 1.2). When the signal is received, a filter analyzes the signal frequencies as a short pulse, erasing the components introduced to make it long (chirp): the result is increased image penetration with an improved signal-to-noise ratio, without compromising axial resolution. Other multi-pulse techniques make use of a coded-emission mode consisting of transmission of an integrated sequence of many short, high-frequency transmission pulses which vary in terms of phase and are modulated in a code sequence. When the signal is received, the signal frequencies are compared with the transmission pulses by a matching decoding filter working at a high sampling rate. The subtraction process results in increased image penetration without loss of axial resolution or an increase in emission peak pulses (Claudon et al. 2002).

Apart from advances in emission pulse technology, broadband transducers use a spectrum of frequency distribution (i.e., 12–5 MHz) instead of a single fundamental frequency (i.e., 10 MHz): the high-frequency components tend to increase the intensity maximum in the focal zone but cause a prompt decrease in intensity with depth, whereas the low-frequency components extend the penetration depth (Whittingham 1999b). In multiple-frequency imaging, the available broad bandwidth is subdivided into multiple frequency steps for transmission and reception of sound waves: these transducers enable selection of the optimal frequency range in a given scanning plane as though two or more independent transducers – each with a different center frequency – were available (Fig. 1.3). Other systems use the total transducer bandwidth for the transmitted pulse and then adjust the receiver bandwidth to lower frequencies as deeper depths are

Technical Requirements

a

b

Fig. 1.2a,b. US pulse shaping. a Intensity versus time diagram illustrates a short pulse wave (arrow) characterized by a few oscillations rapidly dampened by the backing material of the transducer. This short-duration pulse is associated with a broad bandwidth but, when transmitted through tissues, it is rapidly attenuated and absorbed resulting in a poor penetration of the US beam. b Intensity versus time diagram illustrates a chirp pulse. This pulse has a longer duration to increase the penetration of the US beam. It is not a simple sine wave: it is modulated in terms of phase and frequency to include a central component (arrow) – that a receive filter reads as a short pulse to obtain high axial resolution – and two sine queues (arrowheads) on each side of the central component to give penetration capabilities. Example of Chirped Emission (Siemens)

* a

b

c

d Fig. 1.3a–d. Multiple-frequency transducers. a,b Longitudinal US images obtained over the palmar aspect of the hand with a 18–6 MHz multiple frequency transducer by setting the center frequency at a 8 MHz and b 16 MHz respectively. Shifting on the lower frequencies of the bandwidth, penetration (large open arrows) of the field-of-view is achieved; on the other hand, the small superficial cyst (arrowheads) overlying metacarpal bone (thin white arrows) does not appear completely anechoic, subcutaneous tissue echoes are coarse and reverberation artifacts (asterisk) appear deep to the bone. Shifting the frequency band upward, a more defined echotexture is appreciated in the superficial part of the image as a result of an increased resolution. In contrast, a strong attenuation affects the deep part of the US image, which loses intensity. c,d Corresponding intensity versus frequency diagrams illustrate how the frequency band is modulated in multiple-frequency transducers. Example of “eXtreme High-Frequencies imaging” technology (Esaote)

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L. E. Derchi and G. Rizzatto

sampled. These systems give increased flexibility to the US examination, enabling the same transducer to change the image acquisition parameters during scanning based on the desired clinical information. In musculoskeletal imaging, this is particularly important when the study focuses on both superficial (i.e., subcutaneous tissue planes) and deep (i.e., muscle tissue layers) tissues in the same study and body area to be explored.

1.1.1.2 Focusing

Reducing the width and thickness of the US beam has definite advantages in terms of contrast and spatial resolution. In modern linear-array transducers, focusing is currently not obtained by means of a fixed lens as in the old mechanical sector probes in which degrading of the image quality occurred at a short distance from the focal zone (Fig. 1.4a). Focusing is now produced electronically by activating a series of elements in the array with appropriate delays, so that the trigger pulses to the inner elements are delayed with respect to the pulses to the outer ones. In this way a curved wavefront results from constructive interference bringing the US beam toward a focus. By adjusting the values of the delays applied to the trigger pulses, the curvature of the wavefront and, therefore, the focal depth can be changed dynamically. As the resulting wavefront has the characteristics of a short excitation pulse, the axial resolution is preserved. When the pulses are received, the US machine continuously refocuses them according to the position from which the echoes come, thus giving real-time focal tracking along the depth axis: synchronization of the received signals is essential to minimize out-of-axis echo interference. An important factor influencing the lateral resolving power of the system is the dynamic aperture: this is achieved by activating variable numbers of elements dynamically to optimize focusing at many depths. As a rule, the higher the number of channels (electric pathways) involved in this process to activate the elements in a combined mode and with appropriate delays, the higher the complexity and the cost of the equipment, but the more accurately the beam can be focused. Recently, the introduction and refinement of matrix (1.5D probes) transducers led to further progress. In these transducers, the single row of long piezoelectric elements found in a conventional probe is replaced by more layers (three to seven) incorporated into a single thin layer to produce parallel

rows of short elements. The slice thickness of the US image is improved by performing dynamic focusing in the elevation plane (Fig. 1.4b). This leads to better spatial and contrast resolution and reduction of partial-volume averaging artifacts (Rizzatto 1999). A less expensive alternative to 1.5D probes is the use of peculiar acoustic lenses –Hanafy lenses –placed in front of the piezoelectric elements. The Hanafy lens has non-uniform thickness and resonance properties: it produces a narrow and uniform image slice thickness and, simultaneously, a very broad bandwidth pulse. The inner portion of the lens is thinner, resonates at higher frequencies and focuses in the near field, whereas its outer portions resonate at lower frequency and are focused in both transmission and reception at the deepest part of the image providing better penetration (Claudon et al. 2002).

1.1.1.3 Transducer Selection and Handling

A variety of linear-array transducers, including large (>40 mm), medium-sized (4 mm in depth has been regarded as highly sensitive and specific for the diagnosis of necrotizing fasciitis (Yen et al. 2002). In addition, US can reveal loculated abscesses in the fascial plane – allowing US-guided diagnostic aspiration – and gas formation in soft tissues in advanced disease (Robben 2004; Wilson 2004). Gas gangrene, which is produced by organisms of bowel origin or by Clostridium, is an ominous sign (Fig. 2.6b). Aggressive surgical debridement and a course of broad-spectrum antibiotics are critical for the patient’s survival.

2.3.2.3 Fatty Atrophy

Focal reabsorption of the subcutaneous tissue and depigmentation of the overlying skin can be observed following local inadvertent injection of long-acting corticosteroids (Canturk et al. 2004). This “sideeffect” is somewhat related to the catabolic effect of the drug: thinning of the subcutaneous fat is dose-related, may be appreciated up to complete reabsorption of the fatty tissue layer and shows a maximal decrease 4–8 weeks after a single injection of steroids (Gomez et al. 1982). US is a reliable means to confirm the presence of focal shrinkage of the subcutaneous fat by comparing the affected side with either the contralateral healthy side or an adjacent normal area. In clinical practice, focal areas of subcutaneous atrophy may occur around the radial head following steroid injection for treatment of tennis elbow and at the buttock secondary to intramuscular injections. Although the US appearance of subcutaneous atrophy is rather specific, awareness of the clinical history is essential to correlate the US findings with a specific causative factor.

2.3.2.4 Traumatic Injuries

In a traumatic setting, and especially in contusion traumas, changes of the subcutaneous tissue are commonly encountered. Depending on the strength and duration of the insult and the patient’s state

a

b Fig. 2.6a,b. Necrotizing fasciitis. Transverse 12–5 MHz US images over the lower anterolateral leg in a severely compromised diabetic patient with necrotizing fasciitis demonstrate accumulation of fluid along fascial planes (arrows) and scattered bright foci in the soft-tissues refl flecting initial gas formation (arrowheads)

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(anticoagulation therapy, steroids, etc.), soft-tissue abnormalities may range from simple hemorrhagic infiltration of fat lobules, to fat necrosis, hematomas and abscesses. US reveals bloody fat infiltration as an increased echogenicity of fatty lobules that can make the separation from the hyperechoic skin and the connective tissue strands of the subcutaneous tissue undefined (Fig. 2.7a). Hemorrhagic fat infiltration can be readily distinguished from simple edema because of the absence of anechoic fluid distending the connective septa. The differential diagnosis with a superficial hyperechoic lipoma is based on the clinical history and the oval, well-circumscribed appearance of the soft-tissue mass. Following a contusion trauma, subcutaneous fat necrosis may arise with edema, hemorrhage and fibrosis with lack of a discrete soft-tissue mass and volume loss of the subcutaneous tissue (Tsai et al. 1997; Ehara 1998). Fat necrosis appears as a hyperechoic focus containing hypoechoic spaces related to infarcted fat (Fernando et al. 2003) (Fig. 2.7b). In hematomas, the US appearance of the bloody collection varies over time. Soon after the blood leakage, fresh fluid may appear highly reflective up to a pseudosolid appearance because of fibrin and erythrocytes forming multiple acoustic interfaces. With time, the hematoma tends to become completely anechoic as a result of liquefaction of the clot and increases in size (Fig. 2.8a). A network of thin strands may often be seen resulting from fibrin organization (Fig. 2.8b). Fluid levels reflecting separation between serum (anechoic) and cellular com-

a

*

ponents (echogenic) of blood can also be observed. Over a period of months, the hematoma eventually resolves, but a residual fibrous scar and focal retraction of the overlying skin may persist (Fig. 2.8c). As described in Chapter 12, a hematoma that has a peculiar disposition related to the subcutaneous tissue is the Morel-Lavallée lesion. This condition indicates a post-traumatic seroma which derives from local trauma usually located over the lateral aspect of the proximal thigh. The collection typically intervenes between the deep layer of the subcutaneous tissue and the fascia as a result of a shear strain mechanism causing disruption of the rich vascular plexus that pierces the fascia lata (Morel-Lavallée 1863). US depicts a Morel-Lavallée lesion as an elongated fluid collection overlying the straight echogenic appearance of the fascia (Parra et al. 1997; Mellado et al. 2004). In cases of an abscess secondary to trauma, the examiner should attempt to recognize any possible foreign body within it as the causative factor (Fig. 2.9). This is valid even if the patient denies previous open wounds, because the presence of foreign bodies requires surgical removal. In an effort to exclude a more extensive spread of infection that may deserve different treatment, the examiner should check the status of underlying regional muscles, tendon sheaths and joint spaces. Finally, a contusion trauma on the skin by a pointed, sharp object can be transmitted to the subcutaneous tissue causing laceration and focal discontinuity of fat lobules. This category of lesions results in “fat fractures”

*

Fig. 2.7a,b. Subcutaneous tissue contusion trauma and fat necrosis. a Transverse extended-fi field-of-view 12–5 MHz US image of the trochanteric region in a patient with local contusion trauma after a fall demonstrates an undefi fined increased echogenicity of fatty lobules (arrowheads) refl flecting hemorrhagic fat infi filtration. Note that the abnormal area is located just superfi ficial to the osseous prominence of the greater trochanter (asterisk). b Longitudinal 12–5 MHz US image over the anterolateral thigh in another patient with previous local contusion caused by a sharp object. US shows three well-circumscribed hypoechoic areas (arrows) surrounded by ill-defi fined hyperechoic halo (arrowheads) within the subcutaneous tissue (asterisk) representing fat necrosis

b

27

Skin and Subcutaneous Tissue

*

*

a

T b

c Fig. 2.8a–c. Superfi ficial hematoma: spectrum of 12–5 MHz US appearances. a Hematoma of the subcutaneous tissue examined a few days after blunt trauma. US demonstrates an echo-free fl fluid collection (asterisks) reflecting fl the phase of clot liquefaction. b Pretibial hematoma (arrowheads) examined 15 days after trauma reveals closely packed fibrous stranding within the collection refl flecting fibrin organization. T T, tibia. c Residual fibrous scar following a large hematoma in the buttock. US shows the scar as a hyperechoic reflection fl (arrows) with posterior acoustic shadowing (open arrowheads) causing distorsion of the adjacent subcutaneous fat (white arrowheads)

that may mimic a tendon gap at physical examination. US can determine whether the discontinuity is limited to the subcutaneous fat or involves the deeper structures too (Thomas et al. 2001) (Fig. 2.10). Subcutaneous scars are easily depicted with US as vertically -oriented thin linear stripes surrounded by hyperechoic halo that interrupt the normal tissue layers. The abnormal tissue can extend deeply across the fascia into the muscles or the ligaments. Scars may eventually calcify (see Fig. 2.8c).

*

2.3.2.5 Foreign Bodies

Foreign bodies can be found in the subcutaneous tissues as the result of traumatic injuries or therapeutic procedures. In a post-traumatic setting, foreign bodies derive from open or penetrating wounds. Most are composed of plant fragments (wood splinters, thorns, etc.), metal or glass. In terms of prevalence, wood fragments are the most frequently found, fol-

*

a

b Fig. 2.9a,b. Foreign-body-related abscess. a Longitudinal and b transverse 12–5 MHz US images over the dorsum of the hand in a patient with signs of local inflammation fl and a recent open wound. US demonstrates a subcutaneous collection (asterisk) with posterior acoustic enhancement (black arrowheads) and fl fluid-debris levels (open arrowheads). A small highly refl flective foreign body (white arrowhead) is contained within the collection. Surgery revealed an abscess containing a small wood splinter

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* *

* *

*

a

b Fig. 2.10a,b. Subcutaneous fat fracture. a Transverse and b longitudinal 12–5 MHz US images of the gluteal region in a patient with previous local blunt trauma reveal a wide fl fluid-fi filled gap (arrowheads) representing a subcutaneous fat fracture. Note the disrupted appearance of fatty lobules (asterisks) and the alignment of the fracture plane with the edge (white arrow) of the iliac bone

a

d

b

c

e

Fig. 2.11a–e. Foreign bodies: US appearance in two patients presenting with a–c wood and d,e glass fragments. a Long-axis and b short-axis 12–5 MHz US images of a carpenter who injured his left hand during manual work show an elongated hyperechoic foreign-body (arrow) inside the subcutaneous tissue. The fragment is surrounded by a hypoechoic rim (arrowheads) representing reactive edema and granulation tissue. c At surgery, a wood splinter 1 cm long was removed. d Sagittal 12–5 MHz US image of the distal forearm with e radiographic correlation in a patient who had an accident during which he broke a glass with his left hand. Initially, physical exploration was negative for foreign bodies and the wound was sutured. At 3 weeks after trauma, US demonstrated two bright linear images (arrows) with posterior reverberation (arrowheads) refl flecting retained glass fragments in the subcutaneous tissue, just superficial fi to the ulnar nerve (arrowheads). e Radiographic correlation

Skin and Subcutaneous Tissue

lowed by glass and metal fragments (Anderson et al. 1982). Part of them may remain at the site and unrecognized even after apparent successful removal by the patient at the time of the injury (Peterson et al. 2002). If missed, foreign bodies can results in granuloma formation, secondary soft-tissue infection with formation of an abscess, fistula, purulent tenosynovitis and septic arthritis. Bone destructive changes and damage to adjacent nerves may also occur (Choudhari et al. 2001; Peterson et al. 2002). An early diagnosis and prompt removal of foreign bodies is required to prevent complications. Physical examination has intrinsic limitations for detecting and localizing small foreign bodies due to the associated local soft-tissue swelling and pain. It has been reported that approximately 38% of foreign bodies can be overlooked at the initial clinical investigation (Anderson et al. 1982). The deep position of a fragment makes palpation more difficult and less successful. Plain radiography is the initial imaging modality to identify and localize foreign bodies but it can only show radio-opaque fragments: even if very small, metallic fragments are readily detected on plain films. Detection of glass fragments depends on their size and, less importantly, on their lead content, as even if lead-free, almost all glass material is radio-opaque to some degree on radiographs (Felman and Fisher 1969). Radiolucent fragments, such as wood splinters, plant thorns and plastic fragments, cannot be detected by X-rays. Although radiographs allow an estimate of the fragment’s location and its relationships with adjacent bones and joints, in relation with tendons, vessels and nerves cannot be investigated. In addition, local complications are not recognized. Xeroradiography and low-kilovoltage radiography have been proposed to increase the detection rate of foreign bodies, but these techniques are currently obsolete. US is an excellent means of detecting and evaluating post-traumatic foreign bodies (Dean et al. 2003; Soudack et al. 2003; Friedman et al. 2005; Jacobson 2005). In cases of suspected foreign bodies, the examiner should extend the study to a larger area than that closely surrounding the skin wound, as fragments may migrate far away from the entrance point as a result of repeated muscle contraction (Choudhari et al. 2001). As an example, it is not unrealistic to hypothesize that a retained fragment entered the soft tissues on the volar aspect of the wrist may dislocate proximally to reach the anterior distal forearm. As assessed in cadaveric and in vivo studies, the US appearance of foreign bodies varies to a great extent depending on the composi-

tion (metal, glass, wood, etc.), shape and site of the fragment (Blyme et al. 1990; Horton et al. 2001). Either radio-opaque or radiolucent fragments can be identified with US as reflective structures with posterior acoustic shadowing or reverberation artifact, depending on the surface characteristics and composition of the foreign body (Boyse et al. 2001; Horton et al. 2001). In general, wood fragments are characterized by posterior acoustic shadowing, whereas glass and metal exhibit reverberations and comet tail artifact (Fig. 2.11). Although these findings lack specificity, they can help to identify foreign bodies as such. Detection of posterior acoustic artifact is particularly helpful for locating tiny fragments that, because of their small size, can go unnoticed. Similarly, a hypoechoic halo surrounding the fragments is of the utmost importance to distinguish them from adjacent soft-tissue structures, such as fat strands or muscles. As assessed in a comparative US-pathologic study, the halo correlates with fibrin, granulation tissue and collagenous capsule formation, whereas the hypervascular pattern seen at color Doppler imaging reflects neovasculature (Davae et al. 2003). The examiner should be aware that US is not accurate for evaluating the fragment’s size, as the technique is able only to delineate its surface. On the other hand, the relationship of foreign bodies with adjacent vessels, tendons, muscles and nerves can be precisely assessed. US can recognize a variety of complications, including abscess, granuloma, infectious tenosynovitis and septic arthritis (Fig. 2.12). Generally speaking, the main limitations of this technique occur in the acute phases of trauma, when open wounds or soft-tissue emphysema may make the examination difficult. In an acute setting, care should be taken to avoid contamination of the open wound with gel. In these circumstances, the use of sterile gel and a lateral approach to the skin wound can be recommended to image the fragment. If the foreign body is retained in the distal arm or in the distal leg, US examination can be better performed by placing the affected extremity in a water bath (Blaivas et al. 2004). As determined in an in vitro study, air bubbling can decrease the visibility of foreign bodies, leading to attenuation of the US beam deep to the gas (Lyon et al. 2004). In a preoperative setting, US can identify the foreign body, place a skin mark over it and measure the depth of the fragment relative to the skin. As described in Chapter 18, US can guide the removal of superficial foreign bodies during real-time scanning (Shiels et al. 1990). In summary, when a foreign body is suspected on clinical grounds, the examiner should briefly

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* * a

* T

T

*

T

b

T

*

T

c

Fig. 2.12a–c. Tenosynovial foreign body. a Short-axis and b long-axis 15–7 MHz US images over the palm show an elongated wood fragment (curved arrow) that has penetrated within the synovial sheath of the flexor tendons (T). A thin hypoechoic effusion (asterisks) in the tendon sheath allows the fragment to be precisely located in the synovial space. c Short-axis color Doppler 15–7 MHz US image reveals a hypervascular flow fl pattern in the flexor tendon sheath as an expression of reactive hyperemia

discuss the context of trauma with the patient to hear about the nature of possible fragments (glass, wood, metal, etc.). Radiographs should be always performed before US examination. Then, US scanning should cover a wide tissue area around the wound, as foreign bodies may migrate far away from the penetration site. The examiner should seek for bright echoes in the soft tissues but, even more, for structures with posterior acoustic attenuation. Once detected, the fragment should be measured as regards its size, orientation, distance from the skin, and relationships with adjacent tendons, nerves and vessels. Signs of possible infectious complications, such as fluid collections and tenosynovitis, should be annotated as well. Instead of writing a long descriptive report, we prefer to mark the skin overlying the fragment reproducing its size and orientation and to measure the depth of the foreign body: these are important pieces of information for the surgeon before removal. For foreign bodies in deep locations, we recommend appending a drawing to the written report in an effort to better explain the relationship of the foreign body with the adjacent structures. Orthopaedic implants (screws, pins, etc.) can be found in the soft tissues as a consequence of loosening of orthopaedic devices. Metallic devices appear as bright hyperechoic structures with posterior reverberation artifact (Fig. 2.13). Although they are easily detected on plain films, US allows an excellent analysis of the relationship of loosened implants with adjacent structures, thus helping to plan their removal (Grechenig et al. 1999). Implantable subcutaneous devices are used as long-acting and effective methods of contraception. They consist of a single rod implanted in the subcutaneous tissue of

the medial aspect of the arm to release levonorgestrol into the systemic circulation. Based of physical findings, identification of the rod can be difficult if it has inadvertently been inserted too deep or it has migrated away from the insertion point. If removal is required, US is an efficient modality to precisely localize nonpalpable rods, thus allowing their easy removal (Amman et al. 2003; Piessens et al. 2005). Rods appear as a small, elongated, hyperechoic structures with well-defined definite posterior acoustic shadowing, an appearance that correlate well with in vitro findings (Fig. 2.14) (Amman et al. 2003). MR imaging should be used only if US is unrewarding (Merki-Feld et al. 2001). Tissue expanders are widely used in plastic and reconstructive surgery (Neumann 1957). US can assess twisting of injection ports that are surgically inserted into the subcutaneous tissue (Kohler et al. 2005). Twisting is associated with failure of the injection procedure and fluid accumulation in the subcutaneous tissue. US easily demonstrates the upside-down position of the port by showing the linear hyperechoic appearance of the metallic base tilted toward the skin replacing the normal concave superior face of the soft silicone component (Kohler et al. 2005). Suture granulomas may occur after a surgical intervention in which nonabsorbable stitches are used. These tumor-like lesions usually develop slowly and may cause only vague symptoms or remain asymptomatic for many years. US is an accurate way to identify and characterize them by depicting suture material within (Fig. 2.15). As assessed in an in vitro study, the US appearance of surgical sutures is independent of their chemical composition. Monofilament sutures appear as straight bright double lines (like railway

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a

b

Cor

c Fig. 2.13a–c. Loosened surgical screw. a Anteroposterior radiograph of the shoulder with correlative b transverse and c splitscreen sagittal 12–5 MHz US images over the pectoralis region in a patient with a loosened screw (curved arrow) following previous surgery on the shoulder. a Radiograph reveals the loosened screw projecting over the right chest but it does not indicate its precise location. b At US examination, the screw (curved arrow) appears as a hyperechoic structure with posterior reverberation artifact (straight arrows) presenting a head (white arrowhead) and multiple hyperechoic teeth (open arrowheads) at its anterior aspect corresponding to screw spirals. In c, the screw appears as a small hyperechoic dot (curved arrow) surrounded by fluid collection (arrowhead) due to local inflammatory fl reaction. US allows accurate assessment of the relationship of the screw with the short head of the biceps and the coracobrachialis muscles (open arrows) arising from the coracoid (Cor)

lines) due to high-amplitude reflection of the US beam at the superficial and deep interface of the suture with the surrounding tissue; braided sutures most often produce a single echo (Rettenbacher et al. 2001). Both patterns show posterior reverberation artifacts. In general, the surrounding granuloma appears as an ill-defined hypoechoic mass, containing a liquefied center where the stitch lies. The main differential diagnoses are granulomas containing other foreign bodies and inflamed epidermoid cysts containing a hair.

2.3.3 Tumors and Tumor-Like Conditions Soft tissue masses of the subcutaneous tissue include a variety of lesions, such as calcifications, tophaceous gout or rheumatoid nodules, sebaceous cysts

and tumors, ranging from the common lipomas and hemangiomas to the rare metastasis and primary malignant masses. Scattered calcifications in the subcutaneous tissue are observed in scleroderma and systemic lupus erythematosus. They appear as mottled hyperechoic lesions with posterior acoustic shadowing. US has little value in their assessment as they are manifest on plain films. Subcutaneous calcifications are often the result of drug injections. For the most part, they are encountered in the buttock and appear as well-delimited hyperechoic structures with strong posterior acoustic shadowing (Fig. 2.16a). In rheumatologic patients, subcutaneous nodules are mainly due to tophaceous gout or rheumatoid nodules (Tiliakos et al. 1982; Benson et al. 1983; Nalbant et al. 2003). Tophi are softtissue agglomerates of uric acid crystals that can develop in different areas of the body: the hand, the foot and the elbow the most commonly involved.

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a

b

c Fig. 2.14a–c. Subdermal contraceptive device (Implanon). a Short-axis and b long-axis 12–5 MHz US images over a flexible fl subdermal plastic implant (arrows) for long-acting release of synthetic hormones. In selected cases, US can assist in the localization and minimally invasive removal of the implant. c Photograph of an Implanon rod after surgical removal

a

b Fig. 2.15a,b. Suture granuloma. a Long-axis and b short-axis 12–5 MHz US images show a suture granuloma located in the lower abdominal wall after inguinal herniorrhaphy. Within the hypoechoic granuloma (arrows), the surgical suture appears as a hyperechoic rail-like line (arrowheads) when imaged in its long-axis. On the short-axis image, the suture assumes the appearance of a double dot (arrowhead)

At US examination, tophi appear as heterogeneous masses containing hypoechoic areas related to chalky liquid material surrounded by hyperechoic tissue (Nalbant et al. 2003). Rarely, calcific deposits can be detected within the tophaceous mass in the form of hyperechoic spots with or without posterior acoustic attenuation (Fig. 2.16b) (Gerster et al. 2002). Rheumatoid nodules occur in 20–30% of

rheumatoid patients who have a high serum level of rheumatoid factor and active articular disease (McGrath and Fleisher, 1989). They seem to derive from an immune complex process between rheumatoid factor and immunoglobulin G initiating small vessel abnormalities and then progressing to necrosis and granulation tissue. Gross examination of these nodules reveals a semifluid center sur-

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*

* a

b

A

* A

*

A

c

d Fig. 2.16a–d. Non-neoplastic subcutaneous masses. a Elaioma. Transverse 12–5 MHz US image demonstrates dystrophic calcification (arrows) in the subcutaneous tissue of the buttock, at the site of previous injection therapy. b Tophaceous gout. Longitudinal 12–5 MHz US image over the forefoot reveals tophi as para-articular ill-defi fined hypoechoic masses (asterisks) with posterior acoustic shadowing (open arrowheads) and hyperechoic surrounding halo (arrows), adjacent to the MIP joint. Note the osteoarthritic changes (white arrowheads) in the underlying joint. c,d Rheumatoid nodules. c Transverse and d longitudinal 12-5 MHz US images over the Achilles tendon (A) in an HIV-positive patient affected by longstanding rheumatoid arthritis show a rheumatoid nodule as a hypoechoic mass (arrows) arising from the paratenon and growing into the subcutaneous tissue. The nodule has a mixed echotexture with solid (asterisk) and fl fluid (arrowheads) components

rounded by dense connective tissue. Rheumatoid nodules are usually found at pressure sites, such as the extensor aspect of the elbow, the fingers and the calcaneus, and correlate with a bad prognosis. US displays hypoechoic masses with a central sharply demarcated hypoechoic area reflecting necrosis (Fig. 2.16c,d) (Nalbant et al. 2003).

2.3.3.1 Lipomas

Superficial lipomas typically appear as compressible, palpable soft-tissue masses in the subcutaneous tissue not adherent with the overlying skin. Lipomas have a male and familial predominance and tend to grow in the back, shoulder and upper arms with a predilection for the extensor surface. They are more common in the fifth and sixth decades. Although lipomas most often present as a solitary

oval or rounded mass, they may be multiple (5%– 15%) (Murphey et al. 2004). At US examination, lipomas have a wide range of appearances. Typically, they present as elliptical compressible masses containing short linear reflective striations that run parallel to the skin (Fig. 2.17a). However, their internal echogenicity may vary from hyperechoic to hypoechoic or mixed relative to muscle depending on the degree of connective tissue and other reflective interfaces – such as cellularity, fat and water – within the mass (Fornage and Tassin 1991; Ahuja et al. 1998). At least theoretically, it has been postulated that lipomas composed of pure fat should be echofree lesions due to a low number of tissue acoustic interfaces (Behan and Kazam 1978). Based on different series, the incidence of hyperechoic lipomas, reflecting the so-called fibrolipomas, varies from 20% to 76% (Fornage and Tassin 1991; Ahuja et al. 1998; Inampudi et al. 2004). In a recent retrospective review of 39 US-diagnosed superficial and

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c

b

a

* Muscle d

e

Fig. 2.17a–e. Subcutaneous lipoma: spectrum of typical US appearances. a Long-axis extended-fi field-of-view 12–5 MHz US image of a lipoma of the back shows an elongated well-defi fined compressible mass with its greatest diameter parallel to the skin. The mass has well-defi fined margins and appears slightly hyperechoic relative to adjacent fat. Its echotexture consists of short thin linear striations that run parallel to the skin. b Long-axis 12–5 MHz US image at the border of a nonencapsulated lipoma (arrows) in a patient with a palpable mass at the medial aspect of the left thigh with c correlative contralateral image. d Long-axis 12–5 MHz US image of an intrafascial lipoma shows a lenticular fatty mass (asterisk) contained in a split of the muscle fascia (arrows). Note the fascia dividing into two hyperechoic sheets (arrowheads) to envelop the lipoma. e Transverse 12–5 MHz US image of the left forearm in patient with pathologically-proven angiolipoma demonstrates a hyperechoic rounded mass (arrows) with small internal hypoechoic dots

25 lipomas and 14 nonlipomas, including other benign and malignant histotypes (Inampudi et al. 2004). This indicates that the variable echotexture of lipomas may make their differentiation from other masses subjectively difficult. Although many lipomas have a well-circumscribed appearance with an identifiable thin capsule, a significant proportion (12%–60%) have ill-defined borders blending imperceptibly with the surrounding subcutaneous fat (Fig. 2.17b,c) (Fornage and Tassin 1991; Ahuja et al. 1998; Inampudi et al. 2004). This may lead to difficulties in identifying them with US even if the mass is apparent clinically. Nonencapsulated lipomas may require comparison with the contralateral side to detect significant asymmetry of fat tissue. They should be referred to as “probable lipomas” in the report as long as there are corroborative clinical findings of a discrete mass (Roberts et al. 2003).

In daily practice, the occurrence of a superficial palpable lump suggesting a lipoma in the absence of a definite nodule detectable with US is not uncommon. Graded compression with the probe or combined imaging and palpation may be helpful for detecting these “occult” lipomas. Both maneuvers can increase the detection rate of the mass, which is less compressible than the adjacent subcutaneous tissue. Most superficial lipomas do not present substantial internal vasculature at color and power Doppler imaging, a finding that may enhance the confidence of the examiner that a benign mass is present (Ahuja et al. 1998). Some lipomas grow in the deep subcutaneous tissue, in close contact with the fascia. Care should be taken when reporting on these masses not to lead the surgeon to believe that the lesion can be easily excised, because deep subcutaneous lipomas may adhere to the fascia. A well-delimited mass does not always mean an easily

Skin and Subcutaneous Tissue

removable lesion. Lipomas growing inside the deep fascia may also occur. The clinical diagnosis of these lesions may be difficult because they are firm and tethered to the deep plane and may mimic more aggressive tumors. At US examination, intrafascial lipomas appear as lenticular lesions growing into a split of the fascia, which retains a normal hyperechoic appearance (Fig. 2.17d). In these cases, US can rule out abnormalities of the underlying muscles and aggressive growth patterns suggestive of a malignant tumor. Lipomas containing other mesenchymal elements, such as fibrous tissue (fibrous lipomas), cartilage (chondroid lipomas), mucoid component (myxolipoma) and vessels (angiolipoma), may be encountered. In these cases, the presence of nonlipomatous elements may make the US appearance of the lesion less specific. Among these variants, angiolipomas account for 5%–17% of all lipomas (Lin and Lin 1974). They are well-defined hyperechoic subcutaneous masses containing small patchy hypoechoic areas and sparse internal vasculature (Fig. 2.17e) (Choong 2004). Relative to lipomas, angiolipomas have a greater angiomatous component composed of thin-walled capillaries which account for up to 90% or more of the lesion, and occur at an earlier age (early adulthood). Hibernomas (fetal lipomas) are rare benign tumors composed of brown fat. Brown fat is histologically distinct from white adipose tissue and plays a role in nonshivering thermogenesis of hibernating animals and newborn humans. In humans, brown adipose tissue progressively decreases through adulthood. Usual locations of tumors arising from brown fat are the parascapular and interscapular spaces, the mediastinum, the upper thorax and the thighs. US demonstrates a solid well-marginated hyperechoic mass somewhat resembling a lipomatous tumor and Doppler imaging may show a hypervascular pattern reflecting the presence of vascular structures and the increased cellular metabolism of hibernomas. Other rare forms of lipomas, including lipomatosis of nerves (see Chap. 4) and lipoma arborescens (see Chap. 14) are described elsewhere. Other space-occupying nonlipomatous masses containing fat may mimic the US appearance of lipomas. Among them, hemangiomas contain a variable amount of adipose tissue interspersed between abnormal vessels. However, in most cases their typical US appearance made of serpentine or tubular hypoechoic structures contained within the mass, scattered phleboliths and prominent blood flow at

color and power Doppler imaging, allows the correct diagnosis to be made. Lipomatosis represents a diffuse overgrowth of mature adipose tissue histologically similar to simple lipomas. The fatty tissue extensively infiltrates the subcutaneous and muscular tissue and is not associated with nerve involvement. Many entities of superficial lipomatosis are described (Murphey et al. 2004). In multiple symmetric lipomatosis, which is commonly referred to as Madelung or Launois-Bensaude lipomatosis, multiple symmetric lipomas are found in the neck and the shoulder in association with alcoholism, hepatic disease and metabolic disorders (Uglesic et al. 2004). Dercum disease, which is also referred to as lipomatosis dolorosa or adiposis dolorosa, is a rare disorder occurring in middle-aged women, often obese, in which multiple painful subcutaneous lipomas occur (Wortham and Tomlinson 2005).

2.3.3.2 Pilomatricoma and Epidermal Inclusion (Sebaceous) Cysts

Pilomatricoma (pilomatrixoma), also called calcifying epithelioma of Malherbe, is a benign superficial tumor of the hair follicle arising from the hair cortex cells in the deep dermis and extending into subcutaneous tissue as it grows (Malherbe and Chemantais, 1880). Most lesions arise in children less of 10 years of age and appear as small masses (2 kHz) are typically observed and help in distinguishing hemangiomas from other soft-tissue masses (Fig. 2.20b–f) (Dubois et al. 1998, 2002). High-flow malformations are typified by an abnormal network of vascular channels (the nidus), interposed between a prominent feeding artery and a dilated draining

Skin and Subcutaneous Tissue

T

b

a

c

d

Fig. 2.19a–d. Epidermal inclusion cyst. a Lateral radiograph of the middle finger in a patient with a palpable mass on the ventral aspect of the proximal phalanx reveals a superfi ficcial oval soft-tissue mass (arrows). b Transverse 12–5 MHz color Doppler US image of the affected finger demonstrates a wellcircumscribed hypovascular mass (arrows) characterized by a homogeneous texture of medium-level echoes in close relationship with the flexor tendons (T). Correlative c fat-suppressed T2-weighted and d gadolinium-enhanced fatsuppressed T1-weighted MR images show a homogeneous lesion (arrow) of high signal intensity on T2-weighted images, central non-enhancement and peripheral thin rim enhancement. Surgery revealed an epidermal inclusion cyst

d

T

T

a

b

e

c

f

Fig. 2.20a–f. Hemangioma. Transverse a gray-scale and b color Doppler 15–7 MHz US images of the index finger fi in a patient with an indolent palpable mass demonstrate a well-circumscribed solid hypoechoic nodule (arrows) located just superficial fi to the fl flexor tendons (T). The mass reveals several intratumoral vessels. c Coronal fat-suppressed T2-weighted and transverse d T1-weighted, e fat-suppressed T2-weighted and f gadolinium-enhanced T1-weighted MR imaging correlation

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vein. Spectral Doppler analysis demonstrates high systolic arterial flow and arterialization of the veins (Fig. 2.21) (Dubois et al. 1999). Slow-flow (venous) malformations are characterized by abnormally dilated venous spaces and a normal arterial component. Often, they may be suspected on the basis of a subcutaneous bluish or reddish stain. In approximately 15% of cases they contain phleboliths (calcifications in venous thrombosis), which can be seen as hyperechoic foci with posterior acoustic shadowing (Fig. 2.22). Due to slow blood flow, color Doppler imaging may detect only sparse monophasic flow or no blood flow signals at all (Trop et al. 1999). Distinguishing between a slow-flow malformation and an involuted hemangioma may be problematic. In general, vascular malformations are distinguished from hemangiomas owing to the absence of solid tissue (Paltiel et al. 2000). In addition, hemangiomas have similar vessel density and peak systolic velocities but lower venous velocity (Paltiel et al. 2000). Finally, there are capillary malformations limited to the dermis. For the most part, US is unable to display such superficial abnormalities that typically present with a port-wine like stain. In some instances, however, an increased thickness of the subcutaneous tissue and some prominent veins may be demonstrated.

2.3.3.4 Metastases and Lymphomas

Superficial metastases involving the skin and subcutaneous tissue account for approximately 0.5%–9% of tumors. They usually result from seeding of deep tumors during interventional (i.e., needle and surgical biopsy) or surgical procedures or represent a manifestation of end-stage cancer (Galarza and Sosa 2003). In some cases, however, skin metastases can be the first manifestation of an occult cancer, therefore requiring an accurate and early diagnosis (Giovagnorio et al. 2003). Histopathologically, metastases of the skin and subcutaneous tissue can develop from almost any kind of malignancy, but nearly half of them derive from melanoma, lung cancer and breast carcinoma (White 1985). In most cases, metastases appear as well-circumscribed solid hypoechoic masses (Nazarian et al. 1998). A lobulated shape and multiple peripheral vascular pedicles feeding internal irregular vessels seem the most important gray-scale and color Doppler US imaging findings for differentiating them from other benign soft-tissue masses (Fig. 2.23) (Giovagnorio et al. 1999, 2003). In follow-up studies, color Doppler imaging has been proposed as a mean to assess the pharmacodynamic response to chemotherapy

a

b

c Fig. 2.21a–c. Arteriovenous malformation. a Transverse gray-scale 15–7-MHz US image of a 6-month-old infant born with a markedly swollen cheek and upper lip reveals marked thickening of the subcutaneous tissue of the lip (arrows). b Corresponding color Doppler 15–7 MHz US image demonstrates numerous enlarged vessels coursing through the thickened subcutaneous tissue. c Spectral Doppler analysis demonstrates high-velocity arterial waveforms within the vessels

39

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a

c

b Fig. 2.22a–c. Venous malformation. a Longitudinal 12–5 MHz US image of the middle forearm show an ill-defined fi sponge-like subcutaneous mass (arrowheads) containing a network of anechoic channels and a hyperechoic dot (arrow) with posterior acoustic shadowing, likely reflecting fl a phlebolith. b Corresponding 12–5 MHz color Doppler US image reveals only a few, weak signals of flow within the soft-tissue mass (arrowheads). c Radiographic correlation confi firms the presence of a few rounded phleboliths (arrow) within the lesion

* a

c

* b Fig. 2.23a–c. Subcutaneous tissue metastases. a,b Gray-scale and c,d color Doppler 12–5 MHz US images in two patients with previously diagnosed malignancies demonstrate well-defi fined homogeneous hypoechoic nodules (asterisk) located within the subcutaneous tissue. In both nodules, correlative color Doppler imaging shows a hypervascular pattern with peripheral and internal vessels. Postsurgical histologic examination revealed metastases from a,c gut carcinoma and b,d colon adenocarcinoma

d

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by depicting reduction of intratumoral blood flow (Fig. 2.24) (Nazarian et al. 1996). In patients operated on for melanoma, detection of any nonpalpable mass in the subcutaneous tissue or any suspected regional lymphadenopathy should be ascertained by means of US-guided biopsy (Fornage and Lorigan 1989). The subcutaneous tissue can be the primary site of involvement of peripheral T-cell (non-Hodgkin) lymphoma (Lee et al. 2003; Fujii et al. 2004; Giovagnorio 1997). This kind of lymphoma involves the skin and the subcutaneous tissue in two main forms: the cutaneous T-cell lymphoma, which is also known as mycosis fungoides or Sézary syndrome, and the subcutaneous panniculitis-like T-cell lymphoma (Lee et

a

b

al. 2003). Mycosis fungoides is an indolent disorder presenting with cutaneous patches, plaques or erythroderma. With time, the skin lesions may progress to cutaneous tumors, peripheral lymphadenopathies and widespread extracutaneous involvement, with a corresponding drop in patient survival rate. At the stage of tumor formation, US is able to demonstrate diffuse or focal hypoechoic thickening of the skin; the imaging features of this lymphoma are, however, nonspecific (see Fig. 2.3a) (Fornage et al. 1993). The subcutaneous panniculitis-like T-cell lymphoma is a rare condition which may be a diagnostic challenge as it mimics inflammatory cellulitis associated with connective tissue disease (Lee et al. 2003; Sy et al. 2005). This disorder usually presents with multiple

c

Fig. 2.24a–c. Subcutaneous regional metastasis from melanoma. a Gray-scale and b,c color Doppler 15–7 MHz US images in a patient who had a melanoma in his left foot and some regional relapses reveal a small solid homogeneously hypoechoic nodule (arrow) with spiculated margins in the subcutaneous tissue of the left lower leg. The nodule is hypervascular at color Doppler imaging. c After a course of systemic chemotherapy and immunotherapy, the subcutaneous metastasis appears unchanged in size and echotexture but assumes a hypovascular pattern reflecting fl therapy-related change in tumor perfusion

a

b Fig. 2.25a,b. Subcutaneous panniculitis-like T-cell lymphoma. a Gray-scale and b color Doppler 12–5 MHz US images over an hardened ill-defi fined area in the back show diffuse pseudonodular thickening of the subcutaneous tissue (arrows) with a generalized decrease in echogenicity of the fat lobules and a diffuse hypervascular pattern mimicking cellulitis

Skin and Subcutaneous Tissue

palpable subcutaneous nodules, and may undergo rapid deterioration secondary to the onset of the hemophagocytic syndrome (marked anemia due to phagocytosis of red blood cells from monocytes and macrophages). US reveals marked increased echogenicity with swelling of the fat lobules and blurry differentiation between the skin and the subcutaneous tissue, an appearance resembling a diffuse inflammatory infiltrate with edema (Fig. 2.25) (Sy et al. 2005). Hypoechoic nodules surrounded by a hyperechoic rim can also be observed (Fujii et al. 2004). Given the similarity with inflammatory cellulitis, regional enlarged lymph nodes could possibly be misinterpreted as reactive in nature (Sy et al. 2005).

References Ahuja AT, King AD, Kew J et al (1998) Head and neck lipomas: sonographic appearances. AJNR Am J Neuroradiol 19: 505–508 Akesson A, Forsberg L, Hederstrom E (1986) Ultrasound examination of skin thickness in patients with progressive systemic sclerosis (scleroderma). Acta Radiol Diagn 27: 91–94 Amann P, Botta U, Montet X et al (2003) Sonographic detection and localization of a clinically nondetectable subcutaneous contraceptive implant. J Ultrasound Med 22: 855–859 Anderson MA, Newmeyer WL 3rd, Kilgore ES Jr (1982) Diagnosis and treatment of retained foreign bodies in the hand. Am J Surg 144: 63–67 Arslan H, Sakarya ME, Bozkurt M et al (1998) The role of power Doppler sonography in the evaluation of superficial soft tissue abscesses. Eur J Ultrasound 8: 101–106 Behan M, Kazam E (1978) The echographic characteristics of fatty tissues and tumors. Radiology 129: 143–151 Benson CH, Gibson JY, Harisdangkul V (1983) Ultrasound diagnosis of tophaceous and rheumatoid nodules. Arthritis Rheum 26: 696 Blaivas M, Lyon M, Brannam L et al (2004) Water bath evaluation technique for emergency ultrasound of painful superficial structures. Am J Emerg Med 22: 589–593 Blyme PJ, Lind T, Schantz K et al (1990). Ultrasonographic detection of foreign bodies in soft tissue: a human cadaver study. Arch Orthop Trauma Surg 110: 24–25 Boyse TD, Fessell DP, Jacobson JA et al (2001) US of soft-tissue foreign bodies and associated complications with surgical correlation. RadioGraphics 21: 1251–1256 Brenner JS, Cumming WA, Ros PR (1989) Testicular epidermoid cyst: Sonographic and MR findings. AJR Am J Roentgenol 152: 1344 Brocks K, Stender I, Karlsmark T et al (2000) Ultrasonic measurement of skin thickness in patients with systemic sclerosis. Acta Derm Venereol 80: 59–60 Canturk F, Canturk T, Aydin F et al (2004) Cutaneous linear atrophy following intralesional corticosteroid injection in the treatment of tendonitis. Cutis 73: 197–198

Cardinal E, Bureau N, Aubin B et al (2001) Role of ultrasound in musculoskeletal infection. Radiol Clin North Am 39: 191–201 Chau CL, Griffith JF (2005) Musculoskeletal infections: ultrasound appearances. Clin Radiol 60: 49–59 Choong KKL (2004) Sonographic appearance of subcutaneous angiolipomas. J Ultrasound Med 23: 715–717 Choudhari KA, Muthu T, Tan MH (2001) Progressive ulnar neuropathy caused by delayed migration of a foreign body. Br J Neurosurg 15: 263–265 Clements PJ, Hurwitz EL, Wong WK et al (2000) Skin thickness score as a predictor and correlate of outcome in systemic sclerosis. Arthritis Rheum 43: 2445–2454 Davae KC, Sofka CM, DiCarlo E et al (2003) Value of power Doppler imaging and the hypoechoic halo in the sonographic detection of foreign bodies: correlation with histopathologic findings. J Ultrasound Med 22: 1309–1313 Dean AJ, Gronczewski CA, Costantino TG (2003) Technique for emergency medicine bedside ultrasound identification of a radiolucent foreign body. J Emerg Med 24: 303–308 Dubois J, Garel L (1999) Imaging and therapeutic approach of hemangiomas and vascular malformations in the pediatric age group. Pediatr Radiol 29: 879–893 Dubois J, Patriquin HB, Garel L et al (1998) Soft-tissue hemangiomas in children and infants: diagnosis using Doppler ultrasonography. AJR Am J Roentgenol 171: 247–252 Dubois J, Garel L. David M et al (2002) Vascular soft-tissue tumors in infancy: distinguishing features on Doppler sonography. AJR Am J Roentgenol 178: 1541–1545 Ehara S (1998) MR imaging of fat necrosis. AJR Am J Roentgenol 171: 889 Erickson SJ (1997) High-resolution imaging of the musculoskeletal system. Radiology 205: 593–618 Felman AH, Fisher MS (1969) The radiographic detection of glass in soft tissue. Radiology 92: 1529–1531 Fernando RA, Somers S, Edmonson RD et al (2003) Subcutaneous fat necrosis: hypoechoic appearance on sonography. J Ultrasound Med 22: 1387–1390 Fornage BD, Deshayes JL (1986) Ultrasound of normal skin. J Clin Ultrasound 14: 619–622 Fornage BD, Lorigan JG (1989) Sonographic detection and fine-needle aspiration biopsy of nonpalpable recurrent or metastatic melanoma in subcutaneous tissues. J Ultrasound Med 8: 421–424 Fornage BD, Tassin GB (1991) Sonographic appearances of superficial soft tissue lipomas. J Clin Ultrasound 19: 215–220 Fornage BD, McGavran MH, Duvic M et al (1993) Imaging of the skin with 20-MHz US. Radiology 189: 69–76 Friedman DI, Forti RJ, Wall SP et al (2005) The utility of bedside ultrasound and patient perception in detecting soft tissue foreign bodies in children. Pediatr Emerg Care 21: 487–492 Fujii Y, Shinozaki T, Koibuchi H et al (2004) Primary peripheral T-cell lymphoma in subcutaneous tissue: sonographic findings. J Clin Ultrasound 32: 361–364 Galarza M, Sosa FP (2003) Pure subcutaneous seeding from medulloblastoma. Pediatr Neurol 29: 245–249 Gerster JC, Landry M, Dufresne L et al (2002) Imaging of tophaceous gout: computed tomography provides specific images compared with magnetic resonance imaging and ultrasonography. Ann Rheum Dis 61: 52–54 Giovagnorio F (1997) Sonography of cutaneous non-Hodgkin’s lymphomas. Clin Radiol 52: 301–303

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M. Valle and M. P. Zamorani Giovagnorio F, Andreoli C, DeCicco ML (1999) Color Doppler sonography of focal lesions of the skin and subcutaneous tissue. J Ultrasound Med 18: 89–93 Giovagnorio F, Valentini C, Paonessa A (2003) High-resolution and color Doppler sonography in the evaluation of skin metastases. J Ultrasound Med 22: 1017–1022 Gomez EC, Berman B, Miller DL (1982) Ultrasonic assessment of cutaneous atrophy caused by intradermal corticosteroids. J Dermatol Surg Oncol 8: 1071–1074 Grechenig W, Peicha G, Clement HG et al (1999) Ultrasonographic localization of a displaced screw in the carpal canal. A case report. Acta Radiol 40: 625–627 Horton LK, Jacobson JA, Powell A et al (2001) Sonography and radiography of soft-tissue foreign bodies. AJR Am J Roentgenol 176: 1155–1159 Hwang JY, Lee SW, Lee SM (2005) The common ultrasonographic features of pilomatricoma. J Ultrasound Med 24: 1397–1402 Inampudi P, Jacobson JA, Fessell DP et al (2004) Soft-tissue lipomas: accuracy of sonography in diagnosis with pathologic correlation. Radiology 233: 763–767 Jacobson JA (2005) Musculoskeletal ultrasound and MRI: which do I choose? Semin Musculoskelet Radiol 9:135–149 Kohler R, Kritikos N, Poletti PA et al (2005) Sonographic detection of a subcutaneous twisted expander injection port. J Ultrasound Med 24: 1441–1444 Lee HS, Joo KB, Song HT et al (2001) Relationship between sonographic and pathologic findings in epidermal inclusion cysts. J Clin Ultrasound 29: 374–383 Lee HJ, Im JG, Goo JM et al (2003) Peripheral T-cell lymphoma: spectrum of imaging findings with clinical and pathologic features. RadioGraphics 23: 7–28 Lin JJ, Lin F (1974) Two entities in angiolipoma. A study of 459 cases of lipomas with review of literature on infiltrating angiolipoma. Cancer 34: 720–727 Loyer EM, DuBrow RA, David CL et al (1996) Imaging of superficial soft-tissue infections: sonographic findings in cases of cellulitis and abscess. AJR Am J Roentgenol 166: 149–152 Lyon M, Brannam L, Johnson D et al (2004) Detection of soft tissue foreign bodies in the presence of soft tissue gas. J Ultrasound Med 23: 677–681 Malherbe A, Chemantais J (1880) Note sur l’épithélioma calcifie des glandes sebacées. Prog Med 8: 826–837 Maxwell AJ, Mamtora H (1990) Sonographic appearance of epidermoid cyst of the testis. J Clin Ultrasound 18: 188– 190 McGrath MH, Fleisher A (1989) The subcutaneous rheumatoid nodule (1989) Hand Clin 2: 127–135 Mellado JM, Pérez del Palomar L, Diaz L et al (2004) Long standing Morel-Lavallée lesions of the trochanteric region and proximal thigh: MRI features in five patients. AJR Am J Roentgenol 182: 1289–1294 Merki-Feld GS, Brekenfeld C, Migge B, et al (2001) Nonpalpable ultrasonographically not detectable Implanon rods can be localized by magnetic resonance imaging. Contraception 63: 325–328 Morel-Lavallée M (1863) Décollements traumatiques de la peau et des couches sous-jacentes. Arch Gen Med 1: 20–38; 172–200; 300–332 Murphey MD, Carroll JF, Flemming DJ et al (2004) Benign musculoskeletal lipomatous lesions. RadioGraphics 24: 1433–1466

Nalbant S, Corominas H, Hsu B et al (2003) Ultrasonography for assessment of subcutaneous nodules. J Rheumatol 30:1191–1195 Nazarian LN, Alexander AA, Rawool NM et al (1996) Malignant melanoma: impact of superficial US on management. Radiology 199: 273–277 Nazarian LN, Alexander AA, Kurtz AB et al (1998) Superficial melanoma metastases: appearances on gray-scale and color Doppler sonography. AJR Am J Roentgenol 170: 459–463 Nessi R, Betti R, Bencini PL et al (1990) Ultrasonography of nodular and infiltrative lesions of the skin and subcutaneous tissues. J Clin Ultrasound 18: 103–109 Neumann CG (1957). The expansion of an area of skin by progressive distension of a subcutaneous balloon: use of the method for securing skin for subtotal reconstruction of the ear. Plast Reconstr Surg 19: 124–130 Paltiel HJ, Burrow PE, Kozakewich HPW et al (2000) Soft-tissue vascular anomalies: utilities of US for diagnosis. Radiology 214: 747–754 Parra JA, Fernández MA, Encinas B et al (1997) Morel-Lavallée effusions in the thigh. Skeletal Radiol 26: 239–241 Peterson JJ, Bancroft LW, Kransdorf MJ (2002) Wooden foreign bodies: imaging appearance. AJR Am J Roentgenol 178: 557–562 Piessens SG, Palmer DC, Sampson AJ (2005) Ultrasound localization of non-palpable implanon. Aust N Z J Obstet Gynaecol 45:112–116 Rettenbacher T, Macheiner P, Hollerweger A et al (2001) Suture granulomas: sonography enables a correct preoperative diagnosis. Ultrasound Med Biol 27: 343–350 Robben SGF (2004) Ultrasonography of musculoskeletal infections in children. Eur Radiol 14: L65–L67 Roberts CC, Liu PT, Colby TV (2003) Encapsulated versus nonencapsulated superficial fatty masses: a proposed MR imaging classification. AJR Am J Roentgenol 180: 1419–1422 Scheja A, Akesson A (1997) Comparison of high frequency (20 MHz) ultrasound and palpation for the assessment of skin involvement in systemic sclerosis (scleroderma). Clin Exp Rheumatol 15: 283–288 Schmid-Wendtner MH, Burgdorf W (2005) Ultrasound scanning in dermatology. Arch Dermatol 141: 217–224 Shiels WE, Babcock DS, Wilson JL et al (1990) Localization and guided removal of soft-tissue foreign bodies with sonography. AJR Am J Roentgenol 155: 1277–1281 Soudack M, Nachtigal A, Gaitini D (2003) Clinically unsuspected foreign bodies: the importance of sonography. J Ultrasound Med 22: 1381–1385 Struk DW, Munk PL, Lee MJ et al (2001) Imaging of soft-tissue infections. Radiol Clin North Am 39: 277–303 Sy ANL, Lam TPW, Khoo US (2005) Subcutaneous panniculitislike T-cell lymphoma appearing as a breast mass: a difficult and challenging case appearing at an unusual site. J Ultrasound Med 24: 1453–1460 Thomas RH, Holt MD, James SH et al (2001) “Fat fracture”: a physical sign mimicking tendon rupture. J Bone Joint Surg Br 83: 204–205 Tiliakos N, Morales AR, Wilson CH Jr (1982) Use of ultrasound in identifying tophaceous versus rheumatoid nodules. Arthritis Rheum 25: 478–479 Trop I, Dubois J, Guibaud L et al (1999) Soft-tissue venous malformations in pediatric and young adult patients; diagnosis with Doppler US. Radiology 212: 841–845

Skin and Subcutaneous Tissue Tsai TS, Evans HA, Donnelly LF et al (1997) Fat necrosis after trauma: a benign cause of palpable lumps in children. AJR Am J Roentgenol 169: 1623–1626 Uglesic V, Knezevic P, Milic M et al (2004) Madelung syndrome (benign lipomatosis): clinical course and treatment. Scand J Plast Reconstr Surg Hand Surg 38: 240–243 Vincent LM, Parker LA, Mittelstaedt CA (1985) Sonographic appearance of an epidermal inclusion cyst. J Ultrasound Med 4: 609–611

Wilson DJ (2004) Soft-tissue and joint infection. Eur Radiol 14(Suppl 3): 64–71 White JW (1985) Evaluating cancer metastatic to the skin. Geriatrics 40: 67–72 Wortham NC, Tomlinson IP (2005). Dercum’s disease. Skinmed 4: 157–162 Yen ZS, Wang HP, Ma HM et al (2002) Ultrasonographic screening of clinically-suspected necrotizing fasciitis. Acad Emerg Med 9: 1448–1451

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Muscle and Tendon

3

Muscle and Tendon Maria Pia Zamorani and Maura Valle

CONTENTS 3.1 3.1.1 3.1.2 3.1.3 3.1.3.1 3.1.3.2 3.1.4 3.1.4.1 3.1.4.2 3.1.4.3 3.1.5 3.1.5.1 3.1.5.2 3.1.5.3 3.1.6 3.1.6.1 3.1.6.2 3.1.6.3 3.1.6.4 3.1.6.5 3.2 3.2.1 3.2.2 3.2.3 3.2.4 3.2.4.1 3.2.4.2 3.2.5 3.2.5.1 3.2.5.2 3.2.5.3 3.2.6 3.2.6.1 3.2.6.2

Muscle 45 Histologic Considerations 45 Normal US Anatomy and Scanning Technique 46 Anatomical Variants and Heritable Disorders 50 Muscle Agenesis, Anomalous and Accessory Muscles 50 Neuromuscular Disorders 52 Traumatic Lesions 54 Myotendinous Strains 55 Contusion and Laceration 56 Myositis Ossificans 57 Inflammatory and Ischemic Conditions 59 Idiopathic Inflammatory Myopathies 59 Pyomyositis, Abscess, and Hydatid Disease 61 Diabetic Muscle Infarction and Rhabdomyolysis 62 Tumors 64 Intramuscular Hemangioma 64 Deep-Seated Lipoma and Liposarcoma 66 Intramuscular Myxoma 67 Desmoid 69 Rhabdomyosarcoma and Metastases 71 Tendon 71 Histologic Considerations 71 Normal US Anatomy and Scanning Technique 72 Tendon Instability 75 Degenerative Changes and Tendon Tears Tendinosis and Partial Tears 76 Complete Tears and Postoperative Findings Inflammatory Conditions 83 Paratendinitis and Attrition Bursitis 84 Tenosynovitis 85 Enthesopathy 87 Tumors and Tumor-Like Conditions 88 Intratendinous and Tendon Sheath Ganglia Giant Cell Tumor of the Tendon Sheath References

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M. P. Zamorani, MD Unité de Recherche et Dévelopement, Clinique des Grangettes, 7, ch. des Grangettes, 1224 Genève, Switzerland M. Valle, MD Staff Radiologist, Reparto di Radiologia, Istituto Scientifico “Giannina Gaslini”, Largo Gaslini 5, 16148 Genova, Italy

3.1 Muscle 3.1.1 Histologic Considerations On the whole, skeletal muscles can be regarded as the largest organ of the human body, accounting for approximately 25–35% of the total body weight in women and 40–50% in men (Hollman and Hettiger 1990). They are made up of two components: the muscle fibers, which are long and cylindrical in structure, representing the cellular unit of muscle, and stromal connective tissue. Individual muscle fibers are grouped together in bundles, which are commonly known as fascicles, and several fascicles join together to form an individual muscle (Fig. 3.1a). Thin connective tissue strands – the endomysium – separate the individual muscle fibers; a more substantial connective sheath with small vessels and nerve endings, the perimysium (also referred to as fibroadipose septa), envelops individual fascicles; a thick fibrous layer, the epimysium, surrounds the entire muscle (Fig. 3.1a). Muscle fibers vary in length and cross-sectional diameter depending on the individual muscle. Fascicles may be either coarse, as in the case of large muscles, or very fine, as in the case of small muscles that coordinate precise movement (Erickson 1997). They insert into the different connective tissue components of the muscle, including the peripheral epimysium and central major septa formed by converging fibroadipose septa. At their distal end, intramuscular septa join into large tendinous layers – commonly referred to as aponeuroses – or directly to tendons. The internal arrangement of the muscle varies according on the fascicular orientation, which reflects gross muscle shape and function. A parallel arrangement is found in strap-like (e.g., sartorius) and quadrilateral (e.g., thyrohyoid) muscles, in which fibers course nearly the full length of the long axis of the muscle; the rectus abdominis shows

S. Bianchi, C. Martinoli, Ultrasound of the Musculoskeletal System, DOI 10.1007/978-3-540-28163-4_3, © Springer-Verlag Berlin Heidelberg 2007

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Endomysium

Muscle fibers Perimysium

Muscle fascicle

Epimysium a

b Fig. 3.1a,b. Skeletal muscle anatomy. a Schematic drawing illustrates the histologic organization of muscle tissue. Individual muscle fibers are arranged in fascicles. Loose connective tissue strands envelope the fibers (endomysium), the fascicles (perimysium) and the whole muscle (epimysium). b Long-axis 12.5 MHz US image of the medial head of gastrocnemius shows innumerable hyperechoic lines (arrowheads) consistent with perimysium. Note the oblique course of these echoes as they converge toward the aponeurosis (white arrows). The epimysium (open arrows) demarcates the outer boundaries of the muscle

a similar arrangement, but the course of the fibers is interrupted by transversely oriented tendinous intersections (Erickson 1997). Fascicles of fusiform muscles have parallel orientation in the midportion, but they converge toward the tendon at the muscle ends (Fig. 3.2a). An oblique fascicular (feather-like) arrangement relative to the line of traction characterizes pennate muscles (Fig. 3.2b,c). From the biomechanical point of view, the architecture of these muscles increases the insertion surface of fascicles in order to produce a higher force for a given muscle weight. Pennate muscles include triangular-shaped (e.g., adductor longus), unipennate or semipennate (e.g., flexor pollicis longus), bipennate (e.g., rectus femoris), multipennate (e.g., deltoid), and circumpennate (e.g., tibialis anterior) muscles (Erickson 1997). In bipennate muscles, fascicles converge into a single central tendon, whereas multipennate muscles exhibit more than one tendon coursing through the muscle substance. Fascicles may also assume a spiral arrangement in muscles that curve or have a spiral course between the origin and the insertion (e.g., pectoralis major, supinator). In addition, muscles are composed of a single belly or may have a complex internal architecture made up of multiple heads with a different origin (e.g., two heads for the biceps brachii and the biceps femoris; three heads for the triceps brachii and the triceps surae) and join together to generate a distal tendon. From the histologic point of view, muscle fibers can be divided in type 1 (red fibers) and type 2 (white

fibers), which have a different structure, metabolic and functional behavior. Type 1 fibers, which are also referred to as slow-twitch fibers, have a smaller diameter, more blood vessels and myoglobin, and are better suited for slow but prolonged contractions. Type 2 fibers, which are also known as fasttwitch fibers, are larger in size, have fewer blood vessels and a lower myoglobin content, and are capable of powerful contractions of short-duration. Each muscle is made up of a mixture of both fiber types: in some muscles, type 2 fibers are predominant (medial head of gastrocnemius); in others, type 1 fibers are the leading component (soleus muscle). During muscle contraction, the force is transmitted to the skeleton by the tendon or aponeurosis and may or may not result in joint motion. There are three different types of muscle contraction: isometric, when the muscle contracts but there is no change in its length (Fig. 3.3a,d); isotonic, when the muscle contracts and simultaneously shortens (Fig. 3.3b,e); and eccentric, when the muscle contracts and, at the same time, lengthens (Fig. 3.3c,f).

3.1.2 Normal US Anatomy and Scanning Technique When examining muscles, the choice of the appropriate transducer and US frequency band depends on a variety of factors, including the overall size of the muscle belly, its position relative to the skin

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strength

Fig. 3.2a–c. Skeletal muscle anatomy. Schematic drawings demonstrate the internal architecture of skeletal muscles. a Fusiform muscle. The fascicles have a parallel arrangement in the mid-portion of the muscle and converge distally toward the tendon. This leads to a high range of shortening and great movement velocity but results in a low strength. b Unipennate muscle. The fascicles are arranged at an angle to the direction in which the tendon moves and are inserted on one side of the aponeurosis. This results in a greater area of muscle fibers along the axis of contraction and produces more strength at the expense of a reduced range of shortening. c Bipennate muscle. The fascicles insert on two sides of a central aponeurosis. This arrangement produces the highest strength but the lower shortening of the muscle. From the biomechanical point of view, the amount of force that a muscle can generate is proportional to the area of muscle fibers multiplied by the cosine of the muscle-tendon angle

surface (deep or superficial), and the conspicuity of subcutaneous tissue and intervening soft-tissue planes. For an adequate examination, hand muscles require small-sized probes working at high frequencies (frequency band 7–15 MHz), whereas large, deep muscles of the thigh or buttock can be best assessed by means of low-frequency probes (frequency band 3.5–10 MHz). Multiple focal zones should be selected and adjusted to the appropriate depth in order to improve the resolution capabilities over the region of interest. Extended-field-of-view technology greatly increases the ability of US to represent wide and long muscles in a single image as well as to measure the size of large intramuscular lesions, such as hematomas and tumors (Barberie et al. 1998). The patient should be examined in a comfortable position during complete relaxation, isometric and isotonic contraction. Before starting the examination, some notes on the patient’s clinical history should be collected by the examiner with special reference to previous sport trauma (date and mechanism of the injury). Inspection of the affected body area is also needed to rule out local swelling and ecchymosis; then, palpation of the muscle may reveal local tenderness and a mass effect. Especially

Muscle

Tendon Bone a

b

c

in a traumatic setting, an accurate location of the referred pain may help to make the US examination more focused and to shorten the examination time. Then, US scanning is performed by means of long- and short-axis image planes over the affected muscle at rest and during repeated muscle activations. When examining deep muscles, probe compression may help to reduce the thickness of the overlying soft-tissue structures thus making US assessment easier. In patients with muscle hernia, excessive probe pressure may lead to its partial or complete reduction, making the diagnosis difficult. In these cases, the use of generous amount of gel and appropriate patient positioning (i.e. squatting for hemias located in the anterolateral compartment of the leg) to increase the intrafascial pressure may enhance the conspicuousness of the hernia. The size of muscles can be readily assessed with US by means of cross-sectional scanning planes. As measured by dynamometry, differences in muscle size correlate with muscle force (maximal isometric contractions) in both healthy subjects and patients with myositis (Chi-Fishman et al. 2004). Physiologic muscle hypotrophy or hypertrophy can be easily assessed on short-axis US planes: during these measure-

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B

M T a

d

b

e

c

f Fig. 3.3a–f. Muscle biomechanics. a–c Schematic drawings of the muscle (M) – tendon (T) – bone (B) unit with d–f corresponding vector force diagrams illustrate the main types of muscle contraction. White arrows within the muscles and gray arrows in the diagrams indicate contraction. a,d Isometric contraction. The length of the muscle remains the same when it generates tension (arrows) to the tendon. This type of contraction is also referred to as a static contraction and an example is attempting to lift an immovable object or holding a weight at arm’s length. b,e Isotonic contraction. The muscle shortens as it contracts. Many activities involve this type of contraction. An example of isotonic contraction is flexing the biceps muscle to lift an object. c,f Eccentric contraction. This contraction is the opposite of the isotonic. The muscle lengthens as it gains tension (arrows) and the load is very high. An example is walking downstairs or landing on the ground from a jump

ments, care should be taken, however, to avoid any pressure with the probe that can alter the accuracy of measurements and the comparison with the contralateral muscle. Overall, US can be considered a valuable alternative to MR imaging to evaluate the cross-sectional area of muscles and is able to provide information on its changes in response to training or disuse (Reeves et al. 2004). The echotexture of normal skeletal muscles consists of a relatively hypoechoic background reflecting muscle fascicles and clearly demarcated linear hyperechoic strands related to fibroadipose septa (perimysium) (Fig. 3.1b). The intramuscular tendons and aponeuroses appear as hyperechoic bands which are usually better assessed on short-axis images of the muscle (Fig. 3.4). The ratio between the hypoechoic and the hyperechoic components of muscle reflects the proportion between connective tissue and muscle fascicles. It is variable and differs among muscles – for

example, the triceps brachii is less echogenic than the biceps brachii (Walker et al. 2004). The internal pattern of fibroadipose septa displays changes with age (Binzoni et al. 2001). On short-axis scans, the muscle echotexture consists of small dot-like reflectors representing fibroadipose septa interspersed among hypoechoic muscle fascicles (Fig. 3.5a). Although to a lesser extent than in tendons, the ordered structure of fascicles and fibroadipose septa renders muscles anisotropic structures, particularly when examined on short-axis planes (Fig. 3.5a,b). The angle between the US beam and the muscle is critical: an angle that deviates from perpendicular causes the muscle to appear artifactually hypoechoic. On long-axis images, fibroadipose septa appear as straight hyperechoic lines presenting a grossly parallel arrangement. Echoes from fibroadipose septa are less uniform and reflective than those observed in tendons. Depending on the arrangement of muscle fibres and

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T

a

b Fig. 3.4a,b. Intramuscular aponeuroses. a Long-axis and b short-axis 12–5 MHz US images of the normal tibialis anterior muscle (arrowheads) demonstrate the feather-like arrangement of a circumpennate muscle created by the convergence of the fibroadipose septa upon the internal aponeurosis. The aponeurosis (straight arrows) appears as a highly reflective linear echo within the muscle that is thicker than the fibroadipose septa (curved arrow). T, tibia

a

b Fig. 3.5a,b. Muscle anisotropy. Short-axis 17–5 MHz US images of the biceps brachii muscle (arrows) examined with a perpendicular angle between the transducer face and the orientation of the muscle fibers and b an angle that deviates slightly from the perpendicular. In a, the muscle appears diffusely hyperechoic owing to the highest specular reflectivity from the perimysium interfaces. In b, the overall muscle becomes more hypoechoic with decreased intensity of echoes from the perimysium. On the other hand, the larger fibroadipose septa (arrowhead) are more visible. Tilting the probe over the muscle may be useful to distinguish artifactual hypoechoic patterns from mild strains

fibroadipose septa, US is able to recognize the internal architecture of pennate muscles as semipennate, unipennate, bipennate, or multipennate (Fig. 3.6). Intramuscular vessels coursing within the hyperechoic septa are visible on color and power Doppler imaging. The outer muscle fascia (epimysium) appears as a well-delineated echogenic envelope circumscribing the hypoechoic muscle. Large hyperechoic septa (aponeuroses) directed within the muscle belly can be seen arising from it. In complex muscles, an individual hyperechoic fascial sheath surrounds each muscle belly thus helping the examiner to recognize the different heads. The interstice between juxtaposed fasciae of two adjacent muscles appears

as a hypoechoic band and corresponds to loose connective tissue that allows some sliding of the muscles during contraction. Focal interruptions of the muscle fascia are found at the points where nerves, veins, and arteries (perforating vessels) enter the muscles. When the muscle fascia lies under the subcutaneous tissue, it adheres to the superficial fascia and cannot be distinguished from it. Dynamic US scanning performed during muscle contraction can show changes in size and relationship of fascicles and fibroadipose septa. On short-axis planes, contracted muscles usually appear thicker and more hypoechoic. Intramuscular septa change their appearance and orientation as a result of the action of

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a

b Fig. 3.6a,b. Internal architecture of skeletal muscles. a Fusiform muscle. Long-axis 12–5 MHz US image over the deltoid muscle (arrows) demonstrates the fibroadipose septa (arrowheads) as hyperechoic lines separating the hypoechoic muscle bundles. These septa have a parallel arrangement along the muscle belly. b Pennate muscle. Long-axis 125 MHz US image over the tibialis anterior muscle (arrows) demonstrates the fibroadipose septa (arrowheads) as they converge on the highly reflective aponeurosis (curved arrow), giving the appearance of a feather

the muscle fibers that attach into these structures. In the medial head of gastrocnemius, for instance, pennation angle increases from 15.5° to 33.6° when examined during isometric contraction (Fig. 3.7) (Narici et al. 1996). Shortening of muscles is well appreciated on long-axis images during concentric contraction. Recently, a method to measure muscle tissue perfusion by means of contrast-enhanced power Doppler US has been developed with quantification of intramuscular blood flow performed at rest and after exercise (Krix et al. 2005).

3.1.3 Anatomical Variants and Heritable Disorders 3.1.3.1 Muscle Agenesis, Anomalous and Accessory Muscles

Muscle agenesis indicates the absence of one muscle or one head of a complex muscle as a result of incomplete or imperfect development. In general, the diagnosis is already evident at physical examination. US

α

A a

β

A b

Fig. 3.7a,b. Pennation angle. Long-axis 12–5 MHz US images of the medial head of gastrocnemius obtained a at rest and b during isometric contraction demonstrate an increased pennation angle during muscle activation. The pennation angle is given by the incidence of the muscle fibers (dashed line) relative to the aponeurosis (A), which represents the direction of force generation (double arrow). Note that this angle is greater during contraction (β) than at rest (α)

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examination can be required to confirm the clinical findings (Fig. 3.8). An accurate scanning technique is usually needed to differentiate true aplasia from marked hypoplasia or muscle atrophy. As reported in Chapter 6, the pectoralis major and the pectoralis minor muscles are the most common congenitally absent muscles in humans. Both anomalous and accessory muscles are not uncommon developmental abnormalities (Yu and Resnick 1994; Zeiss and Guilluiam-Hadet 1996; Harvie et al. 2004; Kouvalchouk and Fisher 1998). We can define variants of normal muscle anatomy as “anomalous muscles,” and supernumerary muscles that are usually not present as “accessory muscles.” In most cases, anomalous and accessory muscles are unnoticed by the patient because they are invisible and asymptomatic. In some instances, however, they may become clinically relevant. This can occur: when they are apparent on the skin surface mimicking a soft-tissue neoplasm, e.g., reversed palmaris at wrist (Paul et al. 1991; Bianchi et al. 1995b); when they grow within osteofibrous tunnels causing nerve entrapment symptoms, e.g., accessory flexor digitorum longus and tarsal tunnel syndrome

fpl

fpl

FB1

(Pla et al. 1996; Sammarco and Stephens 1990); or when they cause pain during physical exercise, e.g., accessory soleus) due to ischemia related to increased intrafascial pressure or overuse tendinopathy (Peterson et al. 1993). The diagnosis of an anomalous/accessory muscle relies mainly on recognition of its typical location and on imaging features. US demonstrates anomalous/accessory muscles as well-circumscribed elongated structures with the typical echotextural pattern of normal muscles (Montet et al. 2002). A small tendon can be found at the muscle end. Dynamic examination discloses a normal contraction pattern. During muscle activation, short-axis images show increased size and decreased echogenicity of the muscle belly owing to muscle fiber shortening. The most common accessory muscles in the upper and lower limb that are amenable to US examination are: the chondroepitrochlearis at the arm, the anconeus epitrochlearis at the elbow (see Chapter 8) (Masear et al. 1988); the anomalous palmaris longus (Schuurman and van Gils 2000) and Gantzer (al-Qattan 1996) muscles at the forearm (see Chapter 9); the proximal origin of the lumbrical muscles (Timins 1999),

FB2

fpl

fpl

FB1 a

b

FB2 FB1

FB1

c

d Fig. 3.8a–d. Muscle agenesis. Long-axis 12-5 MHz US images over the a left and b right flexor pollicis longus tendon (fpl) in an 8-year-old child with chronic loss of bulk of the left thenar eminence show congenital absence of the superficial belly (FB2) of the flexor pollicis brevis and the abductor pollicis brevis muscles. On the affected side, the flexor pollicis longus tendon assumes a more superficial course given the absence of the muscle. Note the intact deep belly of the flexor pollicis brevis (FB1). c,d Correlative T1-weighted MR images demonstrate the relationship between the flexor pollicis longus tendon (fpl) and the bellies of the flexor pollicis brevis. US is helpful in distinguishing true agenesis from marked hypoplasia or muscle atrophy

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the anomalous muscle belly of the flexor digitorum superficialis of the index finger (Martinoli et al. 2000a), the abductor digiti minimi (Harvie et al. 2003, 2004) and the extensor digitorum brevis manus (Rodriguez-Niedenfuhr et al. 2002) at the wrist and hand (see Chapters 10, 11); the tensor fasciae suralis at the knee (see Chapter 14) (Montet et al. 2002); and the accessory soleus (Bianchi et al. 1995b), the peroneus quartus (Chepuri et al. 2001) (see Chapter 16), and the accessory flexor digitorum longus (Cheung et al. 1999) at the ankle (Fig. 3.9). Familiarity with their most frequent locations and knowledge of the possible clinical syndromes produced by these muscles are the mainstays of a correct imaging diagnosis, thus avoiding confusion

tp

fdl

a v v

with other pathologic conditions and unnecessary surgery. In doubtful cases, US examination of the contralateral side can enhance the confidence of the examiner that an anomalous/accessory muscle is present.

3.1.3.2 Neuromuscular Disorders

In neuromuscular disorders, such as Duchenne and Becker muscular dystrophies, spinal muscle atrophy, and other congenital myopathies, the histologic architecture of muscles is disrupted by muscle cell replacement with connective tissue and fat. This

v a

∗ fhl

v

∗ fhl

a

b

tp fdl

fhl

fhl

∗

fhl

∗ c

d

e

Fig. 3.9a–e. Accessory ankle muscle. a,b Transverse 12-5 MHz US images over the a proximal and b distal medial ankle with c,d T1-weighted MR imaging correlation in a patient with tingling on the medial aspect of the foot extending into the hallux and second toes. US images reveal the anatomic structures contained in the tarsal tunnel, including the tibialis posterior (tp), the flexor digitorum longus (fdl), and the flexor hallucis longus (fhl) tendons, the tibial nerve (arrowhead), and the tibial artery (a) and veins (v). An accessory muscle (asterisk) is found inside the tunnel. This muscle is wedged between the flexor hallucis longus and the flexor retinaculum (arrows), posterior to the neurovascular bundle and refers to the accessory flexor digitorum longus. In this particular case, the accessory muscle caused mild compressive tibial neuropathy. e Schematic drawing through the posteromedial ankle illustrates the relationship of the accessory flexor digitorum longus with the other structures housed in the tarsal tunnel. In most cases, this accessory muscle arises from the posterior aspect of the tibia and the interosseous membrane, running inside the tarsal tunnel to insert into the quadratus plantae or the flexor digitorum longus muscle

Muscle and Tendon

causes profound US changes in muscle architecture with increased echogenicity, loss of heterogeneity, and shadowing (Fig. 3.10). The increased echogenicity of muscle reflects an increased number of acoustic interfaces related to fat accumulation, fibrosis, and inflammation. In neuromuscular disorders, the increased reflectivity of muscles is associated with a decreased ability of the US beam to penetrate deeper structures, leading to loss of bone edge definition and bone shadowing (Fischer et al. 1998; Walker et al. 2004). In addition, the disease process blurs the distinction between fibroadipose septa and muscle fascicles, making the image more homogeneously echogenic (Fig. 3.10a). Similarly, peripheral neuropathies are often associated with selective atrophy of the innervated muscles. US is able to evaluate the size and echotexture of the affected muscles by comparing the two extremities (Scholten et al. 2003). A definite loss in bulk of the affected muscle would suggest atrophy. This can be appreciated by simple pattern recognition analysis (concave or straight muscle boundaries instead of the normal convex surface). Because side-to-side differences in muscle thickness rarely exceed 20%, measuring the muscle diameters or cross-sectional area with the electronic calipers of the equipment seems to be a more reliable means

to assess volume changes in a given group of muscles than subjective evaluation (Bargfrede et al. 1999). The ratio of muscle thickness to subcutaneous fat thickness was found to be helpful in specific neuromuscular disorders (decreased ratio in spinal muscle atrophy). In neuromuscular disorders, however, US has shown some limitations compared with MR imaging. The complex distribution of muscle involvement in some dystrophies seems more reliably mapped with MR imaging because of its better anatomic rendering and panoramic view. Based on echotextural pattern analysis, US is not as accurate as MR imaging in distinguishing early neurogenic atrophy (in which changes are mainly related to extracellular edema) from late atrophy (in which muscle tissue is gradually replaced by fat). Unlike MR imaging, in which early denervation is appreciated by a homogeneous hyperintense pattern on T2-weighted and STIR sequences (increase in free-water content) and late denervation by a hyperintense pattern on T1-weighted images (fatty replacement), at US the two processes have a similar hyperechoic pattern and can be hardly differentiated (Fig. 3.11) (Kullmer et al. 1998). Quantification of muscle echotexture to estimate the severity of atrophy would reduce the observer variability but is strongly influenced by the scanner and the

MHG T soleus F

∗ a

∗ b

c

Fig. 3.10a–c. Neuromuscular disorders. a,b Transverse 12-5 MHz US images obtained over the a posteromedial and b posterolateral aspect of the middle third of the leg in a 12-year-old child with Duchenne dystrophy. The affected medial head of the gastrocnemius (MHG) and soleus exhibits a diffusely hyperechoic pattern with strong US beam attenuation (asterisks) and blurred distinction of fibroadipose septa. The acoustic shadowing leads to inability of the US beam to penetrate deep structures. In b, there is loss of bone edge definition of the fibula (F) caused by the abnormal muscle reflectivity (arrows). T, tibia. c Photograph showing calf muscle pseudohypertrophy. The patient had progressive symmetric muscle weakness associated with elevated serum CK levels, myalgia, cramps, and stiffness after exercise

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T

T a

b

T

T c

d Fig. 3.11a–d. Neurogenic atrophy of muscles in two different patients with a,b recent-onset and c,d long-standing peroneal neuropathy. a Transverse 12–5 MHz US image over the tibialis anterior muscle with b fat-suppressed T2-weighted MR imaging correlation demonstrates normal volume and diffusely hyperechoic appearance of the muscle (arrowheads). The abnormal echotexture is related to intramuscular edema (curved arrow). c Transverse 12-5 MHz US image over the tibialis anterior muscle with d T1-weighted MR imaging correlation reveals decreased volume and hyperechoic appearance of the muscle (arrowheads). Although similar to that seen in a, the abnormal echotexture reflects fatty atrophy (curved arrow). T, tibia

equipment settings (Bargfrede et al. 1999; Pillen et al. 2003; Scholten et al. 2003). Apart from the above limitations, US can be considered a useful tool complementary to electrophysiology to provide information on muscle morphology, which is beyond the scope of electrodiagnosis. In patients with unilateral disorders, US images of the affected muscle can be compared with those of the unaffected side. In these cases, careful positioning of the transducer by surface landmarks is needed to ensure symmetric imaging. Transverse images are best suited for muscle measurements. In patients with bilateral disorders, comparative US evaluation should be conducted by selecting a control muscle in a healthy area, possibly with similar degrees of overlying subcutaneous tissue. Finally, when examining an atrophied fatty-infiltrated muscle, the examiner must be aware that changes may occur not only as a result of a denervation process but also following disuse or a complete tendon tear (Yao and Metha 2003). Then the integrity of the tendon belonging to the affected muscle must be carefully assessed.

3.1.4 Traumatic Lesions Based on their pathomechanism, muscle injuries can be grouped into two main classes: extrinsic and intrinsic. Extrinsic injuries result from external trauma, either a contusion or a penetrating injury (laceration), whereas intrinsic injuries are most often the result of contraction and simultaneous elongation of a given muscle. In the first class, the location of the tear strictly matches the site of the trauma. These lesions typically occur in areas where the muscle is compressed between the applied outer force (direct blow) and an underlying hard bony surface (e.g., quadriceps muscles against the femoral shaft). On the other hand, intrinsic ruptures almost invariably lead to a disruption of muscle fibers near the myotendinous junction, which is considered the weakest ring of the muscle-tendonbone unit because it has less capacity for energy absorption than the other structures (Palmer et al. 1999). The myotendinous junction is the most common site of partial or complete muscle injury

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(Garret 1990). In fact, muscle fibers do not tear just at the myotendinous junction, but rather at a short distance from it (Noonan and Garrett 1999). In the acute phase, the injury is characterized by disruption of the muscle fibers and hemorrhage. The onset of edematous changes and inflammatory infiltrates become obvious by 48 hours after trauma. After a week, fibrous tissue begins to replace the inflammatory reaction forming a scar (Noonan and Garrett 1999). Muscle compartment syndromes are discussed in Chapter 15.

3.1.4.1 Myotendinous Strains

Muscle strains most often occur as a result of powerful stretching when the muscle is contracted. This typically occurs during an eccentric contraction, when the muscle is being lengthened as it activates (Zarins and Ciullo 1983). In these cases, there is

no external cause of trauma and the lesion basically results from an altered equilibrium between two counteracting forces: one produced by forceful, violent contraction of the muscle, the other by concurrent passive muscle overstretching itself, which is usually induced by the body weight. It has been noted that simple activation of normal muscle by nerve stimulation is unable to cause a muscle injury (Noonan and Garrett 1999). Strain lesions are typically located at the myotendinous junction when excessive tensile strength is applied (Fig. 3.12a). Certain muscles are injured more often than others. Muscles used for high-speed activities or rapid acceleration containing a high percentage of type 2 (fast-twitch) fibers are more predisposed to injury. In addition, muscles in which the origin and insertion cross two joints are more at risk for rupture (Noonan and Garrett 1999). The rectus femoris, the biceps femoris, and the medial head of the gastrocnemius display all these risk factors: they cross two joints and acts eccentrically at high speed.

a

b

∗

∗

Qt P Fem

Fig. 3.12a–c. Complete rupture of the distal rectus femoris myotendinous junction. a Schematic drawing illustrates the trauma mechanism occurring along the muscle attachment to the aponeurosis. The injured muscle belly is retracted (arrow) and avulsed from the aponeurosis (curved arrow), whereas the tendon is intact. b Photograph reveals a deep skin defect (arrowhead) in the mid anterior thigh associated with a proximal lump (arrows) related to the retracted rectus femoris. c Extended field-of-view 12–5 MHz US image shows the retracted rectus femoris muscle (open arrows) detached from the distal deep aponeurosis (white arrowhead). A plate-like hematoma (asterisks) separates the muscle from the complex of aponeuroses of the quadriceps (open arrowhead) forming the quadriceps tendon (Qt). Fem, femur; P, patella

c

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M. P. Zamorani and M. Valle

Clinically, muscle strain injuries can be classified into a four-step grading system: grade 1 indicates a tear affecting a small number of muscle fibers with an intact fascia; grade 2 refers to a moderate tear with the fascia remaining intact; grade 3 injury is a tear of many fibers with partial tearing of the fascia; grade 4 injury indicates a complete tear of the muscle and the fascia (Ryan 1969). Healing and recovery of function takes longer with a high-grade injury, and the long-term outcome is generally worse (Noonan and Garrett 1999). Initially, treatment of a muscle strain injury includes rest, application of ice, and compression for relieve of pain and swelling; nonsteroidal inflammatory drugs may also be administered for pain relief in the first days after trauma. After resolution of the acute pain and swelling, physical therapy performed avoiding excessive fatigue and with adequate warm-up before exercise may contribute to the restoration of muscle strength and flexibility (Noonan and Garrett 1999). The long-term outcome after muscle strain injury is usually good and complications are rare. Muscle strain injuries appear at US as avulsion and retraction of muscle fibers from the tendon or aponeurosis in which they attach (Fig. 3.12b,c) (Bianchi et al. 1998). The examiner must be aware that some muscles (e.g., rectus femoris) have a complex structure with internal tendons: in these cases, the injury may occur in the mid-portion of the muscle belly and not at its distal portion as may be expected (Bianchi et al. 2002). US signs of muscle tear include avulsion and proximal retraction of the fibroadipose septa. In low-grade injuries, the space between the retracted septa and the aponeurosis is filled with a hyperechoic area reflecting extravasation of blood and clots. These small lesions may go unnoticed if an accurate scanning technique with careful and systematic examination of the distal portion of the fibroadipose septa is not employed. On the other hand, larger muscle tears are characterized by a more substantial blood collection which makes them easily detectable. This does not occur immediately after the trauma, but 1–2 days later, when the collection tends to become more hypoechoic. A widely accepted classification of muscle injuries is based on a four-grade scale (Peetrons 2002). Grade 0 injury corresponds to a normal US appearance in spite of the presence of local clinical findings; in grade 1 injury, subtle US findings may be observed, including ill-defined hyperechoic or hypoechoic intramuscular areas or a swollen aponeurosis (Fig. 3.13); grade 2 and grade 3 correspond to partial and complete muscle

tears, in which incomplete or full discontinuity of the muscle occurs. In mild trauma, an early assessment with US can lead to false negative results because the hematoma is diffuse and manifests as scattered blurred hyperechoic areas within muscle rather than as a focal well-defined hypoechoic collection: fat-suppressed T2-weighted MR imaging is superior to US in depicting mild strains soon after the trauma. During healing, the hemorrhagic cavity shrinks and its walls progressively thicken and collapse. The time at which the lesion is filled in can be considered an indicator for restarting low-level activity with care. However, this should be only decided in the absence of clinical symptoms and when a sufficient delay has occurred between the injury and the resumption of sports activities (never less than 4–6 weeks after the end of symptoms) (Peetrons 2002). In late phases, fibrous scars are seen as blurred hyperechoic zones within muscle: they are often observed in significant trauma or when the sporting activity was resumed too early (Fig. 3.14) (Peetrons 2002). Usually, scars are weakly symptomatic, but the risk of recurrent injury seems to be proportional to their extent in the muscle.

3.1.4.2 Contusion and Laceration

Direct external trauma may result in local hematoma, contusion, and partial and complete muscle laceration. Although virtually all muscles can be involved during sporting or recreational activities, the most frequently injured are the vastus intermedius and the vastus lateralis. These anterior thigh muscles are particularly predisposed to injury in athletes whose sports require direct hard contact (e.g., soccer, football, rugby, and hockey). The mechanism of injury often consists of crushing of the muscle against the femoral shaft by the knee of another player. Contusion injuries following extrinsic trauma are depicted with US as muscle swelling with focal irregularities and echotextural changes. The muscle architecture is no longer recognized as it is altered by disruption of the muscle fibers and hematoma (Fig. 3.15a). Depending on the overall strength of the applied force, partial or complete tears can occur. Abnormalities are typically located at the actual site of trauma and not at the myotendinous junction: this helps in distinguishing a contusion injury from a muscle strain. If a large fluid collection is present,

Muscle and Tendon

a

b

∗ c

d

e

Fig. 3.13a–e. Myotendinous strains. Two different cases of central aponeurosis strain of the rectus femoris muscle following minimal trauma. a,b Case 1. a Short-axis and b long-axis 12–5 MHz US images over the middle third of the rectus femoris muscle demonstrate an ill-defined hyperechoic area (arrowheads) surrounding the aponeurosis related to edema and hemorrhagic changes. Note the normal-appearing external portion of the muscle (arrows). c–e Case 2. Short-axis 12–5 MHz US images obtained from c proximal to e distal over the rectus femoris reveal progressive swelling and hypoechoic appearance (arrowheads) of the central aponeurosis (straight arrows) and adjacent muscle fibers (curved arrow) with a small hematoma (asterisk) reflecting a myotendinous strain

the muscle ends can be seen floating within the hematoma. Closed muscle trauma by a sharp object may be associated with laceration of the subcutaneous tissue. In these cases, the hematoma expands vertically through the subcutaneous layer and the muscle (Fig. 3.15b). A direct shock injury may also result in disruption of the muscle fascia causing a muscle hernia (Bianchi et al. 1995a; Beggs 2003). In these patients, US demonstrates interruption of the hyperechoic fascial layer and focal extrusion of muscle tissue within the subcutaneous fat (see Chapter 15). Muscle lacerations are much less common and are more often encountered after trauma than after sports accidents. In these instances, irrigation and debridement followed by suture repair of the fascia is indicated.

3.1.4.3 Myositis Ossificans

There are three main complications of muscle tear: cysts and myositis ossificans and, more rarely, calcific myonecrosis (Peetrons 2002). Intermuscular and intramuscular cysts may be encountered after muscle trauma as well-defined echo-free masses with posterior acoustic enhancement. These cysts have an elongated shape and represent the residue of a local hematoma. Their most common location is the calf (see Chapter 15). In selected cases, they may require percutaneous needle evacuation. Calcific myonecrosis is a space-occupying calcified mass that typically develops in the anterior compartment of the leg late after a closed lower extremity

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a

b

c Fig. 3.14a–c. Healing rectus femoris strain. a Long-axis extended field-of-view and b short-axis 17–5 MHz US images of the rectus femoris muscle in a patient with prior myotendinous strain reveal an intramuscular echogenic area (arrows) in proximity to the central aponeurosis (arrowheads) representing residual scar tissue. c Correlative axial gradient-echo T2*-weighted MR image

s

s m

m

m a

b Fig. 3.15a,b. Closed contusion trauma. Two different cases of thigh muscle injuries following blunt trauma by sharp objects. a Transverse 12–5 MHz US image over the vastus lateralis (m) reveals an extensive laceration of muscle tissue filled in with hypoechoic hematoma (arrowheads). Note the intact subcutaneous tissue (s). b Transverse 12-5 MHz US image over the medial thigh demonstrates combined laceration of the subcutaneous tissue (s) and the gracilis muscle (m) with interruption of the fascia (arrows). The defect is filled in with hypoechoic hematoma (arrowheads)

Muscle and Tendon

trauma, and is often seen in association with vascular injury or a compartment syndrome (Dhillon et al. 2004). In this condition, the injured muscle may be replaced with a complex mass consisting of a central cystic core containing necrotic muscle, fibrin, cholesterol, and organizing thrombus, together with a peripheral calcified rim. US demonstrates calcified myonecrosis as an intramuscular extensive calcified mass with posterior acoustic shadowing and may help to guide the aspiration of the fluid component as an aid in management (Batz et al. 2006). The main differential diagnosis of calcific myonecrosis is the more common myositis ossificans, given the fact that the extensive calcified shell may mask the internal fluid component at US examination. Myositis ossificans is a benign self-limiting condition presenting as an intramuscular mass with predominant involvement of the large muscles of the extremities, the large muscles of the thigh and the anterior muscles of the arm being the most commonly affected (Thomas et al. 1991). The term “myositis” is a misnomer because this condition is not inflammatory. It usually results from a severe contusion trauma or chronic microtrauma, but may also be seen in patients with other disease or may develop spontaneously. There is, however, debate as to whether unrecollected trauma is present in these cases. From the histologic point of view, this condition exhibits a typical maturation pattern that allows a proliferative mesenchymal response (early pseudosarcomatous phase) to evolve toward formation of heterotopic mature bone. During maturation of the lesion, a zonal pattern develops with three concentric zones: the inner zone is characterized by areas of hemorrhage and necrotic muscle with proliferating fibroblasts; the middle zone consists of immature osteoid formation and islets of cartilage preceding bone formation; and the outer zone is formed by mature bone (Gindele et al. 2000). Peripheral bone formation usually starts 6–8 weeks after the trauma, but it can occur earlier. In the late phase, the lesion can ossify as a whole with formation of a cortex and marrow spaces (Ackermann 1958). As it matures the lesion regresses in size, disappearing spontaneously in approximately 30% of cases (Schulte et al. 1995). Development of peripheral calcifications is a peculiar feature of myositis ossificans and makes this condition more easily diagnosed with X-ray modalities, including plain films and CT, than with US and MR imaging. In the early stages of disease (before the sixth week of evolution), when formation of calcifications has not yet occurred, the imaging diagnosis is not straightforward: it can be difficult to distinguish lesions at this stage from a soft-tissue malignancy.

The US findings of myositis ossificans change with the lesion’s age, reflecting the evolving histology (Fornage and Eftekhari, 1989; Peck and Metreweli, 1988). Initially, the US appearance of myositis ossificans has been described as that of an intramuscular hypoechoic ovoid mass with an echogenic center, and even a so-called zone phenomenon matching the maturation process has been reported (Kramer et al. 1979; Thomas et al. 1991; Gindele et al. 2000). In more detail, early lesions are characterized by a peripheral thin hypoechoic zone enveloping a broader highly reflective zone within which a third central hypoechoic zone is found (Fig. 3.16a) (Thomas et al. 1991). With progressive maturation, the peripheral hypoechoic rim may become hyperechoic as a result of increasing ossification: a sheet-like or eggshell-like calcified rim is considered very suggestive of myositis ossificans (Peck and Metreweli, 1988). Then, visualization of the lesion center and the separation of the lesion from the underlying bony cortex may become more difficult because of the acoustic shadowing from peripheral calcifications (Gindele et al. 2000). The process of ossification is apparent with US approximately 2 weeks earlier than with plain radiographs (Peetrons 2002). Although the typical pattern of calcifications is characteristic, we believe that a standard radiograph must always be obtained to confirm the diagnosis and to exclude more aggressive calcified lesions, including paraosteal and soft-tissue sarcomas (Fig. 3.16b,c). After surgical resection, US has proved able to detect recurrence of myositis ossificans and to differentiate this condition from extraosseous sarcomas (Okayama et al. 2003).

3.1.5 Inflammatory and Ischemic Conditions Inflammatory myopathies include a heterogeneous group of acquired and potentially treatable disorders caused by an autoimmune process (idiopathic inflammatory myosites) or infectious agents (pyomyositis). Among ischemic conditions, we focus here mainly on diabetic muscle infarction and rhabdomyolysis. As previously stated, compartment syndromes are addressed in Chapter 15.

3.1.5.1 Idiopathic Inflammatory Myopathies

Based on their unique clinical, histopathologic, immunologic, and demographic features, idio-

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a





b

c

Fig. 3.16a–c. Myositis ossificans. a Transverse 10–5 MHz US image over the quadriceps femoris in an 8-year-old child with prior contusion trauma and a painful palpable mass over the anterior thigh reveals a “target pattern” in the vastus intermedius reflecting early changes of myositis ossificans. Three concentric areas can be distinguished: an outer hypoechoic (1), an intermediate hyperechoic (2), and a central hypoechoic (3) zone. b Radiographic and c CT correlation obtained 2 months later demonstrate the typical “eggshell-like” calcified rim (arrows) of myositis ossificans. The CT scan was performed to ensure the extrinsic nature of the calcification relative to the femoral shaft. (Courtesy of Dr. Paolo Tomà, Italy)

pathic inflammatory myopathies can be classified into three major and distinct types: polymyositis, dermatomyositis, and sporadic inclusion-body myositis (Dalakas and Hohlfeld 2003). Polymyositis predominantly affects women and is characterized by the presence of moderate to severe muscle weakness and autoimmune inflammation with lymphohistiocytic infiltrates within muscles, the precise cause of which is still unknown (Garcia 2000). The diagnosis is essentially based on proximal and symmetric muscle weakness with or without pain, increased serum creatine kinase activity, abnormal findings at electromyography, necrosis of muscle fibers, and regeneration and mononuclear cell infiltrates with or without perifascicular atrophy at biopsy (Fig. 3.17). In dermatomyositis, exanthemas (typically involving the face, the chest and the extensor surfaces of the extremities) are associated with the above features. Nevertheless, serum creatine kinase level, in isolation, is a poor indicator of the disease and needle electromyographic signs are not disease-specific (Garcia 2000; Mastaglia et al. 2003). In patients with polymyositis and granulomatous myositis, gray-scale US seems to show increased echogenicity reflecting muscle edema in the acute phases of the disease process, but this sign is nonspecific (Reimers et al. 1993; Reimers and Finkenstaedt 1997). Although fat-suppressed T2-weighted MR imaging is currently the imaging modality of choice in this situation due to its ability to depict muscle edema,

power Doppler US has been proposed as a means to assess muscle vasculature changes in patients with myositis (Newman and Adler 1998; Meng et al. 2001). A hypervascular pattern within muscles was found to correlate with diseases of shorter duration and with creatine kinase activity (Meng et al. 2001). The color Doppler imaging findings varied with the clinical course of disease more than did those of gray-scale US (Meng et al. 2001). In an attempt to quantify muscular capillary perfusion, a recent study based on contrast-enhanced US showed significantly higher blood flow velocity, blood flow, and blood volume in patients with acute myositis than in normal volunteers (Weber et al. 2005). Depiction of an increased muscle perfusion in polymyositis and dermatomyositis may help to identify a suitable biopsy site in patients with typical disease presentation and previous negative or nonspecific biopsy results (Weber et al. 2005). Proliferative myositis is a rare self-limiting intramuscular inflammatory process presenting at a median age of 50 years that may clinically mimic malignancy (Pagonidis et al. 2005). It is characterized by a rapidly growing mass (even doubling in size within a few days) that diffusely infiltrates the muscle tissue with spindle-shaped and giant ganglion cell-like elements. Typically, proliferative myositis heals spontaneously and no treatment is indicated. US may reveal proliferative myositis as a heterogeneous mass with calci-

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a

b Fig. 3.17a,b. Polymyositis and associated scleroderma. a Long-axis and b short-axis 12–5 MHz US images over the medial head of gastrocnemius reveal an intramuscular ill-defined hypoechoic area (arrows) with loss of the fibroadipose pattern, reflecting edema and fatty tissue infiltration. The subcutaneous tissue appears normal

fications (Mulier et al. 1999; Wlachovska et al. 2004). This lesion has been described as having a “scaffolding” pattern between continuous muscle bundles on long-axis scans and a “checkerboard” pattern on short-axis images (Sarteschi et al. 1997). Longitudinal US images may also demonstrate muscle swelling with preservation of the normal fibrillar pattern, disrupted by hypoechoic lines in a geometric shape, somewhat resembling “dry cracked mud” (Fig. 3.18) (Pagonidis et al. 2005). Although imaging studies may suggest such an inflammatory process (very rapidly growing mass in a muscle compartment), incisional biopsy is usually needed to rule out soft-tissue malignancy and to avoid radical excision. Sarcoidosis, a systemic granulomatous disease, may occasionally involve the skeletal muscles, leading to either palpable nodules or chronic progressive wasting and muscle atrophy or acute myositis (Otake 1994; Tohme-Noun et al. 2003). The muscles of the proximal portions of the extremities are predominantly involved. In nodular-type sarcoidosis, US is able to display well-defined hypoechoic nodules elongated along the muscle fibers and to guide percutaneous biopsy to the appropriate site (Levine et al. 1996; Tohme-Noun et al. 2003). Histologic detection of noncaseating granulomas surrounded by normal muscle tissue allows a definitive diagnosis. In large sarcoid nodules, a hyperechoic center can be depicted with US (Otake 1994). In patients with pulmonary sarcoidosis and painful leg muscles, the possibility of muscular sarcoidosis should be taken into account by the examiner. Color Doppler imaging may be helpful to rule out phlebitis.

3.1.5.2 Pyomyositis, Abscess, and Hydatid Disease

Pyomyositis is a suppurative bacterial infection of muscle, most commonly affecting the larger muscles of the lower limb (Chau and Griffith 2005). This condition most often occurs in immunocompromised patients with HIV-AIDS or diabetes and has a higher prevalence in tropical countries, where it is responsible for 3–5% of all hospital admissions (Canoso and Barza 1993; Trusen et al. 2003). However, it may follow even minor blunt trauma and local hematoma. The major causative agent is Staphylococcus aureus followed by Mycobacterium tuberculosis (psoas muscle infection following tuberculous spondylodiscitis), and Streptococcus pyogenes (Bickels et al. 2002). From the clinical point of view, pyomyositis presents with or without fever, dull cramping pain for 10–21 days, and localized muscle tenderness (Trusen et al. 2003). The US appearance of infection of the muscles has been described both in adults (Chau and Griffith 2005) and in children (Trusen et al. 2003). Initially (inflammatory phase), US reveals muscle swelling, a diffuse hyperechoic appearance reflecting edema, and hyperemia (Fig. 3.19) (Bureau et al. 1999; Chau and Griffith 2005). Small hypoechoic foci within the abnormal muscle related to early necrosis and small abscesses may be noted. At this stage, pyomyositis usually responds well to antibiotic therapy. Later in the course of the disease, an overt muscle abscess develops (suppurative phase). Muscle abscesses appear as fluid collections with well-defined posterior enhancement and variable echotexture, ranging from hypoechoic to hyper-

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a

TB

c

TB b

d

e

Fig. 3.18a–e. Proliferative myositis. a Longitudinal 12–5 MHz US image along the temporal muscle in a child with intense softtissue swelling of the left cheek and zygomatic area. The muscle (arrows) appears swollen with hyperechoic bundles separated by randomly distributed hypoechoic lines, a pattern resembling dry, cracked mud. TB, temporal bone. b Normal contralateral side. c Axial and d coronal fat-suppressed T1-weighted and e coronal fat-suppressed T2-weighted MR images demonstrate a swollen hyperintense left temporal muscle (arrows) containing isointense to muscle stripes. Note the normal contralateral temporal muscle (arrowhead) for comparison

echoic (Fig. 3.20) (Bureau et al. 1999). Gas bubbles can occasionally be found within reflecting gas-forming organisms. Color Doppler imaging shows hyperemia of the internal septa and, even more frequently, increased peripheral vascular signals located within the abscess wall or in the surrounding tissue (Gottlieb et al. 1995; Arslan et al. 1998). The late stage yields more profound systemic manifestations that require urgent treatment with aggressive antibiotic therapy. US-guided aspiration and drainage of muscle abscess using large-bore needles is required for complete resolution (Rubens et al. 1997; Bureau et al. 1999). Parasitic and fungal infections of muscle are extremely rare. Among them, hydatid disease is a disease caused by a tape-worm, Echinococcus granulosus, which is usually ingested through contact with dogs or by contaminated food and drink. In the western world, the disease is more often encountered in Mediterranean countries with sheep rearing. Although the preferred site of infection is the liver

(65–75%) and the lung (25–30%), hydatid disease may occasionally involve the musculoskeletal system (1– 5%), including skeletal muscles and subcutaneous fat, usually in association with other liver or lung lesions (Mani et al. 2001; Melis et al. 2002). The psoas and quadriceps seem to be the most commonly involved muscles. The imaging appearance of hydatid cysts is multifaceted (García-Díez et al. 2000). US may suggest the diagnosis only in the case of an intramuscular and intermuscular cyst containing internal rounded cysts, the so-called “cysts within a cyst”, which represent daughter vesicles (Fig. 3.21).

3.1.5.3 Diabetic Muscle Infarction and Rhabdomyolysis

Diabetic muscle infarction is a rare complication of patients with longstanding poorly controlled diabetes mellitus, who usually present with severe indexes of target organ damage, including neph-

Muscle and Tendon

∗ a

b

c

d Fig. 3.19a-d. Pyomyositis in a 65-year-old man with fever and left thigh pain after sustaining blunt trauma to this area. a,b Transverse a gray-scale and b color Doppler 12–5 MHz US images reveal a swollen vastus lateralis muscle with heterogeneous echotexture consisting of increased echogenicity (arrows) as well as hypoechoic areas (asterisk) in which fibroadipose echoes are lost or spaced out. Posterior to this abnormal area, muscle tissue retains a normal appearance (arrowheads). Diffuse intramuscular hyperemia is detected at color Doppler imaging. c,d Correlative axial c T1-weighted and d T2-weighted MR images demonstrate marked hyperintense T2 signal and swelling of the vastus lateralis with irregular borders and diffuse fascial involvement (arrows)

∗

∗ a

F

b

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Fig. 3.20a–c. Muscle abscess. a Transverse 12–5 MHz US image over the anterior thigh in a middle-aged immunocompromised patient with fever, pain, and local signs of infection with b T2-weighted and c Gd-enhanced T1-weighted MR imaging correlation shows a swollen heterogeneous vastus intermedius muscle (arrows) with internal fluid-filled areas (asterisks) and debris, consistent with local abscess formation. F, femoral shaft. US-guided aspiration yielded purulent fluid that grew Staphylococcus aureus up. Symptoms resolved with percutaneous drainage and antibiotic therapy

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b Fig. 3.21a,b. Echinococcosis (hydatid cyst). a Longitudinal 10–5 MHz US image over the lateral thigh with b T2-weighted MR imaging correlation demonstrates an intramuscular complex multilocular mass (arrows) involving the vastus lateralis. The mass contains multiple rounded cysts (arrowhead), reflecting daughter vesicles within the mother cyst. (Courtesy of Dr. Vincenzo Migaleddu, Italy)

ropathy, retinopathy, neuropathy, and hypertension (Chason et al. 1996). This condition seems to be more likely due to extensive thrombosis of medium and small arterioles of muscles rather than embolized atherosclerotic plaque (Jelinek et al. 1999): thigh (the quadriceps) or calf muscles are the most commonly affected (Chason et al. 1996). Clinically, patients with diabetic muscle infarction present with sudden onset of severe local pain, a normal creatine kinase level, and development of a palpable mass in an extremity (Vande Berg et al. 1996; DelaneySathy et al. 2000). From the histopathologic point of view, the affected muscles show infarcted areas with zonal necrosis, foci of hemorrhage with fibers in various stages of degeneration and regeneration, fatty muscle infiltration, and interstitial fibrosis (Jelinek et al. 1999). During the acute phase, US demonstrates diabetic muscle infarction as an intramuscular hypoechoic lesion with mixed echogenicity and internal linear echoes reflecting muscle fibers (Fig. 3.22) (Delaney-Sathy et al. 2000). As the lesion is not compressible, US may help to distinguish it from an abscess. However, the ultimate role of US imaging in this field has yet to be defined. Rhabdomyolysis indicates a process of severe muscle injury characterized by lysis of skeletal muscle cells that may result from a variety of injuries, such as crush trauma, ischemia, toxins, autoimmune inflammatory conditions, and heparin therapy (May et al. 2000). The diagnosis is often missed because clinical symptoms may be indefinite or absent. US demonstrates areas of decreased and increased echogenicity and local disorganization of fascicular architecture of the affected muscles (Lamminen et al. 1989; Steeds

et al. 1999). In acute phases, US may help to detect the affected muscle group for immediate surgical decompression. Further details of the US appearance of rhabdomyolysis are illustrated in the compartment syndromes (see Chapter 15).

3.1.6 Tumors Tumors of the skeletal muscle are rare compared with traumatic lesions. Most of them are benign. However, the occurrence of a malignant neoplasm should be always kept in mind when evaluating a mass, even in a post-traumatic setting, because local trauma does not necessarily exclude the presence of a preexisting tumor. In this section we focus on the US appearance of the most common tumors of muscle, considering the histotypes in which this technique is able to provide the most valuable information. Some histotypes, such as lipomas and hemangiomas, which typically involve muscles but are not of muscular origin, are also discussed here. Intramuscular cysts are addressed in Chapters 6 and 14.

3.1.6.1 Intramuscular Hemangioma

Deep-seated hemangiomas are common benign soft-tissue tumors which often arise within muscles. They predominantly involve the large muscles of the thigh and may be painful if the affected muscle is narrow and long, probably through stretching of

Muscle and Tendon

b

∗ a

c

d

Fig. 3.22a–d. Diabetic infarction. a Anteroposterior plain film of the right leg in a 60-year-old patient with diabetic infarction of the distal lower extremity shows discrete soft-tissue swelling (arrows) in the anterolateral compartment musculature. b Longitudinal 12–5 MHz US image reveals a hypoechoic intramuscular area with deranged echotexture (arrows), which is limited to the tibialis anterior muscle. c,d Axial fat-suppressed c gradient-echo T2* and d gadolinium-enhanced T1-weighted MR images show diffuse edema of the tibialis anterior muscle (arrow) and a ring of high signal intensity after gadolinium administration surrounding an unenhanced central core (asterisk)

the muscle fibers. As already described in Chapter 2, the term “hemangioma” encompasses a wide spectrum of lesions from capillary forms to vascular malformations – including capillary, cavernous, arteriovenous, venous, and mixed types – based on the predominant type of vascular channel involved (Olsen et al. 2004). In addition to their vascular components, hemangiomas can contain thrombus, calcification, hemosiderin, fat, smooth muscle, and fibrous tissue, reactive fat being the most common association. The variety of tissues found in muscular hemangiomas explains their heterogeneous appearance. US demonstrates a complex ill-defined mass within the affected muscle, characterized by a mixture of hypoanechoic and hyperechoic (reactive fat overgrowth) components (Fig. 3.23) (Derchi et al. 1989). Prominent vascular channels can be identified on gray-scale and Doppler imaging as well. One-toone correlation between US and MR images shows good correspondence between intratumor hyper-

echoic areas and fat (high T1 signal), and hypoechoic components and blood-filled cavities (high T2 signal). Phleboliths within the mass are present in approximately 50% of cases and are best identified on plain films (Fig. 3.23f) (Murphey et al. 1995). At US, they appear as bright dots with posterior acoustic shadowing that are usually located within the hypoechoic component of the hemangioma. Doppler imaging characteristics of hemangiomas are described in Chapter 2. Overall, US can diagnose hemangiomas, especially when phleboliths are detected within the mass. During prolonged observation, very slow blood motion in the hypoechoic cavities of the mass can be appreciated on gray-scale imaging, like a “swarming mass”. In some instances, however, the assessment of hemangiomas may be difficult: in particular, the boundaries of the lesion are usually undefined, especially in large masses infiltrating more than one muscle or blending imperceptibly with the intermuscular fatty planes.

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3

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3 2

1

2

b

2

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e

f

Fig. 3.23a–f. Intramuscular hemangioma. a Transverse 12–5 MHz US image over the anterior arm with b T1-weighted MR imaging correlation demonstrates an ill-defined intramuscular mass composed of a mixture of components, including homogeneous hyperechoic tissue (1) related to reactive fat overgrowth, residual muscle tissue (3), and hyperechoic tissue with prominent vascular channels (2). Arrowhead, basilic vein. A split-screen image was used, with the two screens aligned for an extended field of view. c,d A closer look at the vascular component of the hemangioma (2) shows prominent hypoanechoic channels (arrows) characterized by slow blood flow at color Doppler imaging assessment. e Coronal T2-weighted MR image demonstrates the craniocaudal extension of the hemangioma within the biceps brachii muscle. f Lateral radiograph of the arm shows a phlebolith (arrow)

3.1.6.2 Deep-Seated Lipoma and Liposarcoma

Deep-seated lipomas may arise within (intramuscular lipoma) or among muscles (intermuscular lipoma) and are less common than subcutaneous lipomas (Fletcher and Martin-Bates 1988). The intramuscular origin is more common than the intermuscular variant. Lipomas can affect both the muscle and intermuscular connective tissue (Kransdorf et al. 1993; Murphey et al. 2004). The preferred sites of intramuscular lipomas are the large muscle of the extremities (e.g., thigh, trunk, shoulder, and arm). Clinically, they present as slowly growing painless masses but, in some cases, they grow rapidly causing symptoms of nerve entrapment (Muren et al. 1994). Benign intramuscular lipomas can be arbitrarily subdivided into a well-circumscribed type and an infiltrative type. In the former, fatty tissue is clearly delineated from the surrounding muscle. US demonstrates a well-defined ovoid

mass contained inside a muscle with the typical striated appearance of superficial lipomas: a degree of heterogeneity can be related to thin intrinsic septa. In its intramuscular location, the mass is not compressible and no Doppler signal is noted within. Intramuscular lipomas may also become more apparent as distinct masses with muscle contraction. Some lesions appear nearly isoechoic with the adjacent muscle tissue. In these cases, careful scanning technique is needed not to miss even large masses by confusing them with surrounding muscle bellies. In the infiltrative type, there is replacement of muscle tissue in a bland fashion by fat, and muscle fibers are separated by proliferation of fat among them (Matsumoto et al. 1999). At US examination, this produces a heterogeneous striated mass with undefined characteristics that may not resemble a lipoma (Fig. 3.24). One should remember that the infiltrative pattern does not represent a sign of malignancy in intramuscular lipomas. Although the hyperechoic appearance of these masses suggests

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∗ b

∗

∗

∗

a

c Fig. 3.24a–c. Intramuscular lipoma: infiltrative type. a Transverse 12–5 MHz US image over the anterior shoulder in a patient with a painless slowly growing mass with b,c axial T1-weighted MR imaging correlation demonstrates a large mass within the deltoid muscle characterized by a hyperechoic background (asterisks) and a striated pattern (arrowheads) due to intermingled muscle fibers with fat. The lipoma is delimited by a thin hypoechoic rim (arrows) reflecting peripherally displaced muscle tissue

fat, in our experience MR imaging is much superior to US for the confident identification of adipose tissue in infiltrative lipomas. After fibrous and fibrohistocytic malignancies, liposarcoma represents the second most common type of soft-tissue sarcoma, accounting for approximately 10–25% of all soft-tissue sarcomas (Murphey et al. 2005). It is predominant in men around the fifth and sixth decades of life and does not represent the result of malignant transformation of a lipoma. Histopathologically, liposarcomas are grouped in five subtypes: well-differentiated, myxoid, round cell, pleomorphic, and dedifferentiated. Well-differentiated liposarcoma is the most common type (50%); it lacks metastatic potential but tends to recur locally. US shows large, multilobulated, well-defined masses which, in most cases, are indistinguishable from mature lipomas (Fig. 3.25) (Futani et al. 2003; Murphey et al. 2005). Based on gray-scale US findings, lipoma-like lesions with a complex appearance (containing thick septa and nodular or globular foci with echotexture other than that of fat) always merit further investigation with contrast-enhanced MR imaging (Fig. 3.26). Finding blood flow signals in a lipoma-like mass with color and power Doppler imaging should also alert the examiner (Bodner et al. 2002; Futani et al. 2003). Unlike well-differentiated liposarcoma, myxoid liposarcoma presents as a well-circumscribed multinodular mass whose gross pathologic appearance includes a smaller volume of

fat (often