Endoscopic Spinal Surgery [1 ed.] 1907816275, 9781907816277

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ple lele) =)[eSPINAL _ SURGERY

Kai-Uwe Lewandrowski sang-Ho Lee Wilelalatena|e)c=\alelulge)

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ENDOSCOPIC SPINAL SURGERY

ENDOSCOPIC SPINAL SURGERY

Kai-Uwe Lewandrowski MD Orthopaedic Surgeon Center for Advanced Spinal Surgery of Southern Arizona Tucson, Arizona USA

Sang-Ho Lee MD, PhD Chairman of Seoul Wooridul Spine Hospital Department of Neurosurgery Wooridul Spine Hospital Seoul Korea

Menno Iprenburg MD Orthopaedic Surgeon Spine Clinic lprenburg Veenhuizen, Drenthe The Netherlands

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Preface There is no question that there has been a resurgence of endoscopic spinal procedures within the last 5-10 years. This seems predominantly related to patients’ increased interest in minimally invasive procedures, an increased pressure on physicians to market their practices effectively to compete among more educated consumers,

and increased pressure from fee

payers who are looking for more cost effective ways to deliver spine care with improved value and clinical outcomes. Thus, it is no surprise that percutaneous endoscopic procedures have moved from the fringes into the mainstream of spine surgery in the same way as has occurred in other areas of general, orthopaedic, urological, and gynecological surgery, in which laparoscopic cholecystectomy, oophorectomy, prostatectomy and arthroscopic meniscectomy have long been well-established. Simply put, the use of an endoscope has become more acceptable as an alternative to traditional open spinal surgeries, the side effects of which are well recognized by both physicians and patients. This trend towards more minimally invasive interventions in spine surgery is supported by more recent technological advances in the production of contemporary endoscopes, irrigation suction systems, high-definition video and computer equipment, ablative radiofrequency components, and a large array of endoscopic instruments. Increasingly, the latter are designed

to deal with specific clinical problems, such as the treatment of spinal stenosis through the use of highly abrasive drill bits, burrs, and chisels. These newer, more advanced instruments allow the removal of large amounts of bone and soft tissue, thereby paving the way for more meaningful and effective treatment of relevant clinical conditions that, in terms of clinical outcomes, are at least comparable to open spinal procedures, This new text, Endoscopic Spinal Surgery, attempts to provide the reader with a snapshot of the contemporary procedures for treating common conditions of the cervical, thoracic, and lumbar

spine percutaneously by the use of advanced instrumentation and technologies. Furthermore, it provides the reader with a synopsis of the fundamentals of endoscopic spine surgery, by discussing its historical background, clinically relevant aspects of applied physics and optics, choice of anesthesia, indications, appropriate patient selection, and expected clinical outcomes. We hope that this new text will motivate the reader to become more interested in endoscopic spinal surgery.

Kai-Uwe Lewandrowski Menno Iprenburg Sang-Ho Lee

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Contents EI

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Preface

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Contributors

ix

Chapter 1 Spinal endoscopy: historical perspectives

1

Kai-Uwe Lewandrowski

Chapter 2

Instruments for spinal endoscopy Kai-Uwe Lewandrowski

7

Chapter 3 Relevant neuroanatomy of the lumbar motion segment J. N. Alastair Gibson

13

Chapter 4 Anesthetic consideration for endoscopic spinal surgery Alexander Godschalx

21

Chapter 5 Anterior percutaneous cervical discectomy Michael Schubert

PA

Chapter 6 Percutaneous endoscopic cervical discectomy and stabilization Yong Ahn

33

Chapter 7 Endoscopic anterior cervical discectomy Alvaro Dowling

39

Chapter 8 Posterior cervical, endoscopically assisted microdiscectomy and foraminotomy Jin-Sung Kim Chapter 9 Full endoscopic, posterior cervical foraminotomy and discectomy for cervical radiculopathy Marion R. McMillan

45

49

Chapter 10 Endoscopically assisted posterior cervical foraminotomy Alvaro Dowling

57

Chapter 11 Percutaneous endoscopic thoracic discectomy and facetoplasty Ho-Yeon Lee, Sang Hoon Jang

67

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Chapter 12 Thoracoscopic discectomy Sang Hyeop Jeon, Sang-Ho Lee

75

Chapter 13 CT-guided percutaneous endoscopic thoracic discectomy Ho-Yeong Kang

79

Chapter 14 Thoracoscopically assisted mini-thoracotomy, corpectomy, and fusion Dae Hyeon Maeng

87

Chapter 15 Percutaneous endoscopic lumbar discectomy: transforaminal approach June Ho Lee

Chapter 16 Percutaneous endoscopic lumbar discectomy: pros and cons of outside-in versus inside-out technique Michael Schubert Chapter 17 Percutaneous endoscopic lumbar discectomy: interlaminar approach Gun Choi, Sang-Ho Lee, Abhishek Kashyap, Guilherme Meyer Chapter 18 Percutaneous endoscopic lumbar foraminoplasty Won-Chul Choi Chapter 19 Percutaneous endoscopic lumbar annuloplasty

95

99

107

117

121

Chan-Shik Shim, Sang-Ho Lee

Chapter 20 Endoscopically assisted transforaminal percutaneous lumbar interbody fusion Rudolf Morgenstern, Christian Morgenstern

Chapter 21 Endoscopy of the aging spine Ralf Wagner

127

BS

Chapter 22 Technique, clinical results, and indications for transforaminal

lumbar endoscopic surgery

143

Kai-Uwe Lewandrowski

Chapter 23 Complications after lumbar spinal endoscopy Menno Iprenburg

151

Chapter 24 Procedural classification and coding problems Marion R. McMillan, Kai-Uwe Lewandrowski

155

Index

159

Contributors Pe ODES EEE ITI

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Yong Ahn, MD, PhD Department of Neurosurgery Seoul Wooridul Spine Hospital Seoul Korea

Ho-Yeong Kang, MD Department of Interventional Radiology Busan Dongrae Wooridul Spine Hospital Busan Korea

Gun Choi, MD, PhD Department of Neurosurgery Seoul Gimpo Airport Wooridul Spine Hospital Seoul Korea

Abhishek Kashyap, MS Assistant Professor of Orthopaedics Central Institute Of Orthopaedics VMMC and Safdarjung Hospital New Delhi India

Won-Chul Choi, MD

Department of Neurosurgery Seoul Gangbuk Wooridul Spine Hospital Seoul Korea

Alvaro Dowling, MD Orthopedic Surgeon/Spine Surgeon Member of SCHOT (Chilean Society of Orthopaedic Surgeons) Member of SICCMI (Interamerican Society of Minimal Invasive Spine Surgery) Head, Director of Endoscopic Spine Clinic Santiago Chile

J. N. Alastair Gibson, MD, FRCSEd, FRCS(Tr & Orth) Consultant Spinal Surgeon Department of Orthopaedic Surgery The Royal Infirmary and University of Edinburgh Edinburgh UK Alexander Godschalx, MD Anesthesiologist/Pain Specialist Wilhelmina Hospital Assen Spine Clinic lprenburg Veenhuizen Drenthe The Netherlands Sang Hoon Jang, MD Department of Neurosurgery Seoul Gangbuk Wooridul Spine Hospital Seoul Korea Sang Hyeop Jeon, MD Department of Cardiothoracic Surgery Seoul Gimpo Airport Wooridul Spine Hospital Seoul Korea

Jin-Sung Kim, MD, PhD Associate Professor of Neurosurgery Department of Neurosurgery Seoul St. Mary’s Hospital The Catholic University of Korea Seoul Korea Ho-Yeon Lee, MD, PhD Department of Neurosurgery Seoul Gangbuk Wooridul Spine Hospital Seoul Korea June Ho Lee, MD Department of Neurosurgery Seoul Wooridul Spine Hospital Seoul Korea

Marion R. McMillan, MD Director, Spinal Medicine and Endoscopic Spinal Surgery Synergy Spine Center Seneca, South Carolina USA Dae Hyeon Maeng, MD Department of Thoracic and Cardiovascular Surgery Seoul Wooridul Spine Hospital Seoul Korea

Guilherme P. C. Meyer, MD Orthopaedic and Spine Surgery Orthopaedic Department Hospital Israelita Albert Einstein Sao Paulo Brazil

Christian Morgenstern, MD, PhD Orthopaedic Resident Charité - Universitatsmedizin Berlin Centrum fiir Muskuloskeletale Chirurgie Berlin Germany Rudolf Morgenstern, MD, PhD Orthopaedic Spine Surgeon Morgenstern Spine Institute Centro Médico Teknon Barcelona Spain Michael Schubert, MD

Orthopaedic Surgeon/Spine Specialist Apex Spine Center Munich Germany

Chan-Shik Shim, MD, PhD Medical Director Wooridul Spine Center Dubai UAE Ralf Wagner, MD Orthopaedic Specialist/Spinal Surgeon Ligamenta Spine Centre Frankfurt Germany

Chapter 1

Spinal endoscopy: historical perspectives Kai-Uwe Lewandrowski

@ INTRODUCTION Surgical decompression of neural elements and stabilization of unstable spinal motion segments have been the main goals of spinal surgery regardless of what type of technologies are used to achieve these goals. Often, this requires extensive exposure and stripping of soft tissues, which in turn may devitalize and degenerate the very structures, the integrity of which is paramount to maintaining a healthy spinal motion segment. Problems such as postlaminectomy instability and epidural fibrosis have long been recognized as some of the potential follow-up problems that could arise from traditional open spinal surgery.!* Other well-recognized problems include disruption of vascular supply and denervation of paraspinal muscles with resultant decreased trunk strength, and chronic pain syndromes that at least in part arise from extensive spinal exposures.’ At 10 years, the cumulative rate of development of adjacent level disease in both the cervical and the lumbar spine, in previously healthy spinal motion segments adjacent to fusions, has been reported to be as high as 25%. This is not a small number and recognition of this problem has prompted surgeons to look for alternative ways to accomplish the two basic goals of each spinal surgical procedure: neural element decompression and stabilization of unstable motion segments.*® From the patient’s point of view, reduction of blood loss and surgical time, with rapid recovery and return to work, is a clear advantage that nowadays is being openly discussed. With the advent of the internet, social media hubs, and blogs, and the overall availability of educational information, patients have become much more educated, inquisitive,

at times critical, and hopeful that their specific problem can be solved with less aggressive procedures. From a surgeon’s point of view, these advantages are no less important because they seem to drive patient traffic into their offices, and to present a number of clinical upsides that can easily be communicated to patients, families, hospitals, insurance carriers, third party payers, and medical review boards. Nevertheless, the question remains whether these minimally invasive procedures will withstand the test of time and show at least a similar track record when it comes to long-term clinical outcomes. This is obviously the area where opinions diverge the most and where discussions are most controversial. In this chapter, the author attempts to summarize, without any claim on completeness, how the current state-of-the-art endoscopic

spinal surgery progressed from a simple discectomy procedure to an array of sophisticated methods that have largely evolved from advances in high-definition optics, computerized irrigation/suction systems, production of durable endoscopic instrumentation, and incorporation of technologies well proven in other medical areas such as radiofrequency ablation and lasers.

Mi HISTORY OF LUMBAR ENDOSCOPIC SPINAL SURGERY the first microdiscectomy procedures for radicular pain due to herniated disc were performed by Mixter and Barr in 1934. They reported on 19 patients who underwent laminectomy.° The concept of a less aggressive decompression was first introduced by Hult, who performed nucleotomy through an extraperitoneal approach in 1951." In the 1960s, the concept of chemonucleolysis evolved after Lyman and Smith discovered that percutaneous injection of chymopapain could hydrolyze a herniated nucleus pulposus in a patient with sciatica due to the herniated disc." In 1973, Parvis Kambin introduced the concept ofa transforaminal

approach with the use of percutaneously placed Craig’s cannulas through which he performed microdiscectomy in a nonvisualized fashion.'? Hijikata reported on nonvisualized psoterolateral percutaneous nucleotomy in 1975.'° William Friedman introduced the direct lateral approach for percutaneous nucleotomy in 1983 and reported that this procedure was associated with a higher rate of bowel injury." The introduction of a specially modified arthroscope into the intervertebral disc, and thus the first visualized microdiscectomy, was first

reported by Forst and Hausman in 1983." The addition of a motorized shaver was described by Onik in 1985 which led to the coining of the term ‘automated percutaneous nucleotomy. Kambin published his first ‘discoscopic views’ from within the disc in 1988 and later emphasized the importance of epidural visualization as well.’ One year later, Schreiber described the injection of indigo carmine dye into the disc to stain abnormal nucleus pulposus and annular fissures."* Kambin first described the ‘safe’ or ‘working’ zone in 1990 as the triangle bordered by the exiting nerve root, the inferior endplate and superior articular process of the inferior vertebra, and medially

by the traversing nerve root (Figure 1.1).!° Better understanding of the anatomy of the working triangle paved the way for introduction of larger working cannulas for introduction of more sophisticated instruments and endoscopes (Figure 1.2).”° Endoscopes with an angled optic were introduced by Schreiber in 1993, allowing dorsal vision around an annular tear.'* Kambin and Zhou demonstrated the use of a 30° endoscope, recognizing that lateral recess stenosis can hamper effectiveness of the procedure. In 1996, they demonstrated foraminoplasty via endoscopic removal of facet overhang, osteophytes, and annulectomy, using specialized forceps and trephines.”°?! Foley, Mathes, and Ditsworth furthered the field of endo-

scopic spinal surgery by popularizing the transforaminal approach in their clinical studies published between 1998 and 1999.” In 1999,

Yeung introduced the Yeung Endoscopic Spine System (YESS™)

SPINAL ENDOSCOPY: HISTORICAL PERSPECTIVES =

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Another leap forward was achieved by Ruetten et al. who dealt with the problem of poor visualization of the epidural space, with the popularization of the direct lateral approach and uniportal use ofa foraminoscope.*” Hoogland and Schubert dealt with the problem in an alternative way by describing foraminoplasty with transforaminal reamers in 2005.*' This technique made it easier to gain access to sequestered disc fragments that migrated in locations far distant from the interspace. This problem was further analyzed by Lee, in 2006, who found that patients with severe canal and lateral recess

Figure 1.1 Surgical anatomy of the ‘safe zone’ The safe zone is formed by the lateral border ofthe exiting nerve root above, medially by the border of the traversing root or thecal sack, inferiorly by the endplate, and dorsally by the superior articular process ofthe inferior vertebral body. The safe zone is located within the axilla between the exiting and traversing nerve roots. (Redrawn from an original by Robert F. McLain in: Lewandrowski K-U, Yeung CA, Spoonamore MJ, McLain RF (eds). Minimally Invasive Spinal Fusion Techniques. 2008, Summit Communications).

Figure 1.2 The‘safe zone’ is entered by removing parts of the superior articular process of the inferior vertebral body, thus performing a foraminoplasty. (Redrawn from an original by Robert F. McLain in: Lewandrowski K-U,

Yeung CA, Spoonamore MJ, McLain RF (eds). Minimally Invasive Spinal Fusion Techniques. 2008, Summit Communications).

using a multichannel, wide-angled endoscope.” In 2001, Knight et al. showed that endoscopic foraminoplasty with a side firing Ho:YAG (holium:yttrium-aluminum-garnet) laser can be effective in neural element decompression.”° The advent of lasers also stimulated electrothermal annuloplasty for low back pain, which was described by Tsou and Yeung in 2002.” More contemporary systems were introduced by Antony Yeung in 2003 with the launch of the YESS, which was designed around the transforaminal endoscopic approach for intradiscal and epiduroscopic procedures.” Yeung et al. describe the utility of provocative intraoperative discography, thermal discoplasty and annuloplasty, and annular resection for creation of an annular window to perform foraminoplasty with the use of abrasive drills, burrs, and lasers. Bipolar electrofrequency probes were introduced by Tsou who performed a thermal electroannuloplasty for chronic discogenic low back pain. This technique was done on the direct visualization targeting disc nucleus and annular fissures.”

stenosis had less risk for remnant symptoms.” Lee et al. also sification system

favorable clinical outcomes as a result of a higher disc fragments responsible for persistent clinical pioneered the definition and application of a clasfor the location of herniated disc by dividing them

into near-migrated (zone 2 and zone 3), and upward (zone 1) or

downward (zone 4) far-migrated disc fragments.** The author’s own clinical experience underlines the importance of the use of radiographic classification systems for both herniated disc and spinal stenosis. The utility of a radiographic classification system for foraminal and lateral recess stenosis is demonstrated in Chapter 22 of this text, where division of the neuroforamen into entry, mid-, and exit zones

has been shown to be helpful when stratifying patients and selecting appropriate surgical candidates.

Mi HISTORY OF CERVICAL ENDOSCOPIC SPINAL SURGERY The first to report on percutaneous cervical discectomy in 1989 was most likely Tajima et al.,34 and Gastambide (1993)** independently reported on manually removing the central portion of a cervical disc without removal of the posterior longitudinal ligament under fluoroscopic guidance. This process produced an indirect decompression. Algara et al. developed an automated percutaneous cervical discectomy procedure in 1993.*° Herman also reported on automated nonendoscopic discectomy 1 year later.*” Bonati (1991),** Sieber (1993),°° and Hellinger (1994) reported on the utility of laser percutaneous cervical discectomy. Lee et al. introduced the combined use of percutaneous manual and laser discectomy in 1993 and later popularized the concept of ‘laser-assisted spinal endoscopy.’ This system was based on a straight firing Ho:YAG laser that was introduced through an illuminated and irrigated 3-mm flexible cable. In 1994, Zweifel published on experimental laser disc surgery, pointing out that the Ho:YAG laser was the safest but most effective laser for tissue ablation while minimizing thermal damage to surrounding tissues. Chymopapain has been used in the mid-1990s but was later abandoned because of catastrophic clinical complications.” Another technological break was achieved with the introduction of a 0°, 4-mm

endoscope with a 1.9-mm working channel

(Figure 1.3). Surgeons at the Wooridul Spine Hospital in Seoul, South Korea took advantage of improved endoscopic visualization, and a large working channel.* Ahn et al. reported that 88.3% of their 111 percutaneous anterior cervical discectomy patients improved

at a mean follow-up of 49.9 months. Loss of mean disc height was later analyzed in a smaller series of 36 patients and was limited.

to 11.2%, suggesting that sagittal alignment could be maintained without development of postoperative segmental instability or spontaneous fusion with the use of the percutaneous anterior cervical discectomy procedure.“

Teme

Radiofrequency ablation eae aE

amount of energy through a small fiber in a very focused small area. This has first been demonstrated by Peter Ascher who employed a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser through an 18-gauge needle that was introduced fluoroscopically into the intervertebral disc. °° He ablated intradiscal tissue in short bursts to avoid heating of adjacent tissues, thereby vaporizing tissue that was allowed to escape through the needle. This procedure was ideally suitable for an outpatient setting - as the patient was discharged, the needle was withdrawn, and the puncture wound covered with

a small Band-Aid. Many subsequent authors demonstrated the utility of different types of lasers including the Ho:YAG which was compared with the Nd:YAG laser in a clinical trial conducted by Quigley et al. in 1991. They concluded that the Ho:YAG laser was the best for compromising between efficacy of absorption and convenience of fiberoptic delivery at that time. In 1990, Davis et al. described a 85% success rate Figure 1.3 Anterior 20° cervical endoscopic system with instruments (asap Endosystems GmbH, Umkirch, Germany).

@ BRIEF CHRONOLOGICAL SYNOPSIS OF CLINICAL OUTCOME STUDIES Until recently, randomized prospective trials comparing the traditional open versus the endoscopically performed lumbar microdiscectomy procedure were unavailable. Earlier studies, however, suggested that successful outcomes can be achieved, e.g. Choi et al. reported a 92% success rate with their own extraforaminal fragmentectomy technique. In their 2007 study, they reported on 41 patients in whom soft extraforaminal disc herniations were treated in such a way with a more medialized trajectory.* In the same year, Lee et al. demonstrated high

clinical success rates with downward migrated disc fragments (91.8%), in upward migrated disc fragments (88.9%), in near-migrated disc fragments (97%), and slightly less favorable clinical results with farmigrated disc fragments (78.9%).°”° The type of herniation is obviously the hardest to reach and demands proficient surgical skills. Ruetten et al. published results of 463 patients treated with the endoscopic transforaminal discectomy procedure.” In 2009, Ruetten et al. published the results on surgical treatment for lumbar lateral recess stenosis using the full endoscopic and interlaminar approach versus conventional microsurgical technique. This prospective randomized controlled trial on 161 patients showed similar clinical results in the ‘full endoscopic group’ and the microsurgical group when analyzing the German version of the North American Spine Society instrument and the Oswestry low back pain disability questionnaire.*® In the cervical area, Chiu reported outcomes on 200 patients whom he treated with percutaneous microdecompressive endoscopic cervical discectomy, with a side-firing Ho:YAG laser. At 25 months of average follow-up he reported a 94.5% success rate in the absence of major clinical complications.”

MM THE EVOLUTION OF LASERS IN LUMBAR MICRODISCECTOMY Lasers have always been very attractive for surgeons when applied in minimally invasive procedures due to the ability to deliver a large

in a study on 40 patients who underwent laser discectomy using the potassium titanic phosphate (KTP 532-nm) laser. Only 6 of the 40 patients required revision with open discectomy procedures because of clinical failures. In 1995, Casper et al. described the use of the side-firing Ho:YAG laser® which was also later employed by Yeung et al.°* At 1-year follow-up, Casper et al. reported an 84% success rate.™ In the same year, Siebert et al. reported an 78% success rate on 100 patients with a mean follow-up of 17 months who were treated with

the Nd:YAG laser.*° Mayer et al. was the first to suggest the combined use of an endoscope with laser ablation through an endoscopically introduced fiber. Large clinical trials followed and were very supportive of the clinical use of lasers for removal of herniated disc.** Hellinger reported in 1999 on more than 2500 patients whom he treated with the use of the Ascher technique.” He reported the success rate of 80% over a 13-year period. One year later, Yeung et al. reported an 84% success rate on more than 500 patients whom he treated with the KTP laser.™

RADIOFREQUENCY ABLATION High-frequency radiofrequency (RF) ablation has found several applications in neurosurgery, endoscopic spine, orthopedic and pain management. High-frequency RF with low temperatures has been employed for tissue dissection (monopolar) and coagulating mode (mono- and bipolar). For spinal endoscopy, the Trigger-Flex

Bipolar System (Elliquence, New York, USA) has been developed to accomplish targeted application and precise tissue ablation (Figure 1.4). The Trigger-Flex Bipolar System is compatible with all working channel spinal endoscopes and is used for hemostasis, shrinkage, or ablative effects in soft tissue to dissect them off a herniated disc. RF ablation of tissues is well accepted in other areas such as plastic surgery, oral maxillofacial surgery, and dental procedures. These devices have found their way into spinal surgery for thermal ablation of disc tissue. With further miniaturization and reduced acquisition costs, they now present an attractive alternative to lasers which in most cases are more costly and cumbersome, and impose certain safety issues for patients, surgeons, and supporting staff alike. The utility of high-frequency RF with low-temperature tissue ablation has been investigated in at least one study. In 2004, Tsou et al. retrospectively reviewed 113 consecutive patients with a minimum postoperative follow-up of 2 years. Patients were treated for discogenic low back pain:

SPINAL ENDOSCOPY: HISTORICAL PERSPECTIVES

Figure 1.4 (a) Trigger-Flex Bipolar System (Elliquence, NY, USA) introduced through the central working channel for tissue ablation. (b) Squeezing the hand piece will flex the tip: the probe is connected to a generator.

Using the surgeon assessment method, 17 patients (15%) had excel-

lent results, 32 patients (28.3%) had good results, 34 patients (30.1%) had fair results and 30 patients (26.5%) had poor results. Of the 30 patients in the poor result group, 12 reported either no improvement or worsening, and refused further surgical treatment. Of the remaining 18 patients in the poor group, 8 had spinal fusion, 3 had laminectomy and 7 had repeat spinal endoscopic surgery. The patient-based questionnaire yielded similar percentages in each category. However, only

73.5% of the 113 patients returned the survey questionnaire. There were no aborted procedures, unexpected hemorrhage, device-related complications, neurologic deficits, perioperative deaths or late instability. The authors concluded that the treatment interrupted the purported annular defect pain sensitization process. Nowadays, high-frequency RF with low-temperature tissue ablation is an integral part of spinal endoscopy, and is most useful when controlling bleeding and shrinking tissue to facilitate decompression.

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Chapter 2

Instruments for spinal endoscopy Kai-Uwe Lewandrowski

INTRODUCTION Endoscopic systems for spinal surgery are in principle no different from systems designed for arthroscopic examination of large joints, or laparoscopes designed for surgery of the abdominal cavity. At heart, they consist of an endoscope, video camera, light source with cable, a video processing unit, video monitor, and video or photographic recording devices. Most endoscopes for the spine employ a rigid rodlens design connected to a body, which has attachments for irrigation fluid, suction, and a video camera. The last can be in the form of a

generic oculus design to accommodate video cameras from different manufacturers, or it can be a specialized attachment mechanism for a specific video camera system. Designs vary by manufacturer and a number of proprietary systems have been developed. In this chapter, the author attempts to discuss some of the technical aspects of spinal endoscopy with respect to design rationales for endoscope and instruments that are used together with the spinal endoscope during surgery. The chapter is intended merely as an overview from a surgeon’s point of view and primarily discusses how

particular technical and design considerations are relevant to certain procedural aspects during the spinal decompression procedure.

lM BASIC COMPONENTS OF ~ASPINAL ENDOSCOPY The purpose of the spinal endoscope is no different from an operating room microscope: illumination and magnification. Compared with an operating room microscope, the endoscopes can be placed directly over the area of interest at great depth inside the human body, and thus provide an unobstructed view of the surgical area in great focus. Spinal endoscopes are unique in that they are multichannel endoscopes. Typically, they have one small irrigation and one suction channel each, and a larger central working channel. Unlike in arthroscopes, the central working channel is used to perform the surgery. Earlier designs had an inner diameter (ID) working channel of 3.5 mm. More contemporary foraminoscopes designed for transforaminal surgery have an ID working channel of 4.1 mm, thus allowing use of a number of standard neurosurgical instruments ' with an outer diameter (OD) of 4.0 mm. Newer modifications embody an elliptical design of the outer sheath, which improves flow of irrigation fluid when fitted in a round access cannula. The optic is usually angled 20° or 30°, and 0° spinal endoscopes are preferred in the cervical spine for a ‘head-on’ view onto the herniated disc. An

angled field of view allows visualization of a larger area and looking around corners, but does take some getting used to as far as handling, orientation, perspective, and navigation.

i INSTRUMENTS FOR SPINAL ENDOSC OPY In principle, endoscopic spinal surgery instruments are designed for use in a similar way to instruments intended for open surgery. However, they are much longer to fit through the central working channel, reach the pathology inside the patient, and clear the video camera assembly attached to the end of the endoscope. ‘Therefore, typical instrument length for lumbar spinal endoscopy ranges from 280 mm to 300 mm, and a typical length for an instrument for cervical spinal endoscopy is about 200 mm. Some instruments have depth markings, and most have straight tips with a fixed hinged tip, making it possible to reach for tissue at an angle away from the center line of the instruments. The length of the tip of a typical pituitary rongeur can range from 3 mm to 10 mm, thereby determining the amount of tissue that can be grabbed and the distance from the centerline that can be reached. Some designs have curved tips to improve reach around corners at shorter distances. Contemporary rongeur-type instruments should have a breaking point in the handle that will fail before breaking the cross-pin in the hinge of the angulated tip. This will ensure that the instruments can be retrieved in its entirety from the patient, even if failing during surgery. Failure of instruments without a predetermined breaking point in the handle may detach the articulating tip of the rongeur while working inside the spinal canal. Small metal foreign bodies such as this can be extremely difficult to retrieve without additional open surgery. Longer instruments may dampen the tactile feedback when handling tissue for which the surgeon has also to rely heavily on visual appearance of the tissue when performing dissection and decompression maneuvers. A good three-dimensional understanding of the anatomy is crucial to carrying out the operation safely. This obviously may be an initial obstacle, which may take some getting used to for the novice. In general, instruments for spinal endoscopy can be classified into five categories: 1. Instruments grabbing soft tissue, such as rigid instruments, forceps,

and pituitary rongeurs 2. Instruments for removing bone, such as reamers, trephines, and chisels 3. Instruments for tissue ablation, such as radiofrequency probes for anticoagulation, tissue annealing, or shrinking 4. Motorized instruments such as high-speed drills and burrs 5. Lasers for tissue ablation, such as the holmium:yttrium-alumi-

num-garnet (Ho:YAG). In this chapter, the author focuses on describing instruments for lumbar endoscopic surgery.

INSTRUMENTS FOR SPINAL ENDOSCOPY

M@ ENDOSCOPIC SYSTEMS The basic design ofa spinal endoscope consists ofa long tubular casing containing the rod-lens assembly, fiberoptic cable for light transmission, working, irrigation, and suction channels, and a body with an eyepiece (Figure 2.1). The last also has attachments for fiberoptic light cable, and irrigation and suction tubing, as well as the video camera. Numerous variations of this design are available from several manufacturers. Some examples of different designs of lumbar endoscopes are shown in Table 2.1.

Figure 2.2 Spinal approach 16-gauge needle used for guidewire placement and administration of local anesthesia or discography during surgery (asap Endosystems Gmbh).

M@ INSTRUMENTS FOR PLACEMENT OF THE ENDOSCOPE Reliable insertion of the endoscope can be accomplished with long 16-, 18-, or 20-gauge spinal approach needles, stainless steel or nitinol guidewires, solid or cannulated sequential dilators, and a working sheath (Figure 2.2). Once the approach needle is in satisfactory position, it can be replaced with a guidewire (Figure 2.3). A single large-diameter cannulated obturator can be inserted over the guidewire (Figure 2.4). Alternatively, several cannulated dilators of increasing diameters can be placed over each other to sequentially dilate the approach portal

Figure 2.3 Nitinol guide wire outer diameter 1.65 mm, length 400 mm (asap Endosystems Gmbh).

for placement of the working cannula (Figures 2.5, 2.6, and 2.7). The use of nitinol has the advantage of avoiding kinks in the guidewire Figure 2.4 Sharp cannulated obturator, inner diameter 1.7 mm, outer

diameter 7.0 mm, length 250 mm (asap Endosystems GmbH).

Figure 2.1 Lumbar foraminoscope with 4.1-mm inner working channel manufactured by asap Endosystems GmbH (Umkirch Germany).

Figure 2.5 Sharp cannulated obturator, inner diameter 1.7 mm, outer diameter 7.0 mm, length 250 mm (asap Endosystems Gmbh).

Table 2.1 Examples of available lumbar endoscopes

Scope dimension

a

|

Opti

| 58x5.0mm

| 5.9x 5.0 mm, 6.9 x 5.6 mm

| Configuration: working channel, rod-lens

Configuration: larger working channel, small | fiberoptic system, one irrigation channels |

| system, two irrigation channels

H

Working length | Diameter inner working channel Opticangle

Working «cannula sleeve outerrdiameter | Working cannula sleeve inner diameter

205 mm for transforaminal approach 165 mm for interlaminar approach

| 6.9x6.1 mm

Bone-cutting instruments

Figure 2.8 Endoscopic mallet with nonrepercussive plastic head.

Se——————_—

Figure 2.9 Hammer driver used to advance endoscopic working sheath.

Figure 2.6 (a) Cannulated dilators over nitinol guide wire. (b) Cannulated dilators and nitinol guide wire shown separately. (asap Endosystems Gmbh).

DISCECTOMY INSTRUMENTS Endoscopic forceps and pituitary rongeurs can be used for the discectomy procedure. Larger-diameter forceps are passed directly through the working cannula because their OD exceeds the size of the inner working channel. The diameter of these fluoroscopic forceps and pituitary rongeurs ranges from 5 mm to 6 mm. There is a wide array of endoscopic forceps that can be passed through the inner working channel of the endoscope, thus allowing to surgeon perform the discectomy procedure under direct visualization

(Figures 2.10-2.14). The OD of these instruments ranges from

Figure 2.7 Working sheath inner diameter 7.1 mm, outer diameter 8 mm; (a-c) beveled, beaked, and fenestrated tip.

when dilators are placed forcibly or against resistance. The tip of the dilators or obturators can be sharp or blunt and is typically tapered to facilitate tissue dilation. The working sheath is an oval or cylindrical tubular retractor that is

_placed over the final dilator or (single-step) obturator. The latter is then removed and the endoscope can be inserted for direct visualization of spinal and neural structures. The outer and inner diameters for lumbar endoscopes typically range between 7 and 8 mm. Working cannulas can have several tip designs. A beveled tip design is useful in most cases, but beaked and fenestrated tip designs may proof useful for retraction of neural structures, epidural fat, and veins.

The working sheath can be advanced manually or hammered in place with a small mallet (Figure 2.8) and a hammer driver

(Figure 2.9).

2.5mm to 3.785 mm and is often dictated by the ID of the endoscope’s central working channel. Articulating forceps (Figure 2.15) may be for the more advanced surgeon and may be useful when retrieving a downward or upward migrated extruded disc fragment. Dissecting instruments including rigid and flexible probes and flat tips, may be useful in dissecting out the intervertebral disc from adjacent tissues, such as capsular and foraminal ligaments, epidural tissue, and blood vessels (Figures 2.16 and 2.17).

| BONE-CUTTING INSTRUMENTS Several types of instruments are available for bone cutting with the lumbar endoscopic procedure. These range from chisels, burrs, drills, and reamers, to trephines (Figures 2.18 and 2.19). They are often used in a foraminoplasty procedure during a transforaminal approach, or for lateral recess decompression during an interlaminar approach. Drills and burrs can be used ona handle and be advanced manually. Alternatively, they can be attached to a power drill. Some companies have their own proprietary systems with specific modifications. One example is a combined shaver drill. Many of the

Figure 2.10 Endoscopic micro-spoon grasping forceps, outer diameter 3.0 mm.

Figure 2.15 Enlarged view of the tip of angulated hinging forceps scissors, outer diameter 3.0 mm.

Figure 2.11 Enlarged view of the tip of the endoscopic micro-spoon grasping forceps, outer diameter 3.0 mm.

Figure 2.16 Enlarged view of a fixed-tip dissecting tool, outer diameter 3.0 mm.

Figure 2.12 Enlarged view of the tip of a down biting endoscopic grasping forceps, outer diameter 3.5 mm.

Figure 2.17 Enlarged view of the tip of a flexible hinging dissecting tool, outer diameter 3.0 mm.

Figure 2.13 Endoscopic micro-spoon grasping forceps, outer diameter 3.5mm.

Figure 2.14 Enlarged view of the tip of a micro-spoon endoscopic grasping forceps, outer diameter 3.5 mm.

Figure 2.18 Enlarged view of the tip of a blunt side-cutting rasp, outer diameter 5.0 mm.

motorized power decompression tools have sheathed designs and are disposable. Sheathed designs have the advantage of minimizing cavitation of the decompression instrument, but tend to be disposable and have limited ability to evacuate debris from the surgical site because the inner working channel is almost entirely occupied

with the device. Unsheathed drill or burr designs tend to be more abrasive because they permit larger cutting heads. Thus, a rapid decompression is possible. This design should perhaps be reserved for the more advanced surgeon because no protective hoods prevent advancing the instrument towards the neural elements. Other more

Further reading

minimal leakage and controlled in- and outflow seem preferable. High-flow situations should be avoided because irrigation fluid can travel distant to the surgery site and, in rare cases, can generate spinal headaches.

lm ENDOSCOPY TOWER A designated endoscopy cart is best in settings where the surgery suite is used for multiple different procedures. On a dedicated cart, the equipment can easily be moved around while minimizing the risk of missing equipment or faulty connections between components as a result of multiple take-downs and set-ups. A typical setup is shown in Figure 2.20. Figure 2.19 Enlarged view of the tip of a end-cutting trephine, outer

diameter 5.0 mm.

advanced drill/shaver devices with flexible tips allowing decompression around a 90° corner have recently been introduced. Again, use of these instruments requires experience and understanding of the lumbar spinal anatomy.

VIDEO EQUIPMENT Most endoscopic systems are organized in a tower containing a light

source, a video/digital video recorder (DVR) system, and a photographic documentation system. Some endoscopes have proprietary

camera attachments whereas most have a generic oculus to which a standard quick-release endoscopic box CCD (charged coupling device) video camera can be attached. They can easily be rotated about the endoscope, thus allowing the field of view to be rotated to the area of interest. Three-chip cameras display the highest resolution and light sensitivity but are also most costly. The image/video signal from the CCD camera is processed, optimized for contrast and sharpness, and relayed to the video monitor. The signal can also be recorded by a DVR. Most systems will also allow printing of a still image on to photographic paper. More advanced systems allow voice annotation and offer integrated documentation systems that produce surgical reports with images and video footage as deemed appropriate by the surgeon. The choice of light source and video monitor is also important. A xenon light source and a high-definition color video monitor are recommended. The monitor should be at least 20 inches (51 cm)

in size and is ideally placed at the surgeon’s eye level.

li IRRIGATION SYSTEM Spinal endoscopy is done under constant irrigation. This requires a reservoir, and inflow and outflow. The fluid can be fed by gravity _ or with a roller pump. The latter provides for more accurate setting of irrigation flow and pressures. The inflow is through the irrigation channel of the endoscope. The outflow is through the sheath and the working channel. Physiological (0.9%) saline in 3-liter irrigation bags is usually appropriate. Some surgeons add antibiotics or epinephrine to the solution to minimize the risk of postoperative infection, and the amount of bleeding during surgery. This author uses just 0.9% saline without any additives for irrigation. In this author’s opinion, pressure-controlled systems are more useful because they allow better control of bleeding during surgery. Therefore, systems with

Mi FURTHER READING Kim DH, Choi G, Lee S-H. Endoscopic Spine Procedures. New York: Thieme, 2011; chapter 2. Kim DH, Fessler R, Regan J. Endoscopic Spine Surgery and Instrumentation. New York: Thieme, 2004; chapter 2.

Figure 2.20 Endoscopy tower with high-definition

video processing unit and screen, light source recording unit, and printer.

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