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Endoscopic Spine Surgery: Past, Present, and Future.

As society continues to enjoy the fruits of technological advancements, there is a fervor for medical innovation to elevate our ability to effectively and eloquently address pathology. Over the past 50 years, the field of spine surgery has seen an increasing emphasis in techniques designed to minimize iatrogenic tissue trauma and, hence, reduce postoperative pain and disability. The conceptual goals of "minimally invasive spine surgery" echo the Hippocratic aphorism "do no harm." There is a philosophical paradigm shift that must take place that is predicated upon a precision diagnosis and a targeted treatment that considers patient comorbidities and short-term and long-term expectations. The emphasis on decreasing muscle crush injuries during prolonged retraction, avoiding soft tissue stripping and muscular denervation, minimizing bony resection to prevent iatrogenic instability, and utilizing a surgical corridor that allows targeted access to spinal pathology are all principles that every spine surgeon should employ when treating patients. Endoscopic spine surgical techniques represent another tool in the armamentarium of the spine surgeon to treat spinal pathology using these principles.

History of Endoscopic Spine Surgery

The Rise of Arthroscopic Surgery

The desire to develop technology to provide access to different closed body cavities has existed for centuries. From the creation of the "gazogene cystoscope" in 1806, which provided light by the combustion of gasoline and turpentine that was reflected into the bladder by a mirror, to the first cystoscope utilizing an incandescent bulb for illumination in 1886, (1) technological advancements have led to adoption of endoscopic techniques in almost all the surgical subspecialties. (2) The 20th Century witnessed the rise of arthroscopic surgery, which has undoubtedly changed the field of orthopedic surgery. In the early 1930s, Dr. Michael Burman of the New York Hospital for Joint Diseases explored the use of an arthroscope in the laboratory using a special 4-mm diameter endoscopic instrument. (3) Burman was also credited for introducing the concept of myeloscopy for direct spinal cord visualization, (4) with Pool introducing the concept of intrathecal endoscopy or myeloscopy in 1942. (5) With advancements in television and video recording technology, Dr. Masaki Watanabe from the University of Tokyo performed the first partial meniscectomy under endoscopic control in 1962 using a specially designed Watanbe arthroscope. (2) Although arthroscopy continued to evolve with continued technological advancements and gained widespread appeal in orthopedic surgery, endoscopic techniques were largely abandoned in spine surgery due to the morbidity associated with insertion of a large-bore endoscope into the dural cavity. (6) It was not until the early 1970s when endoscopic spine surgery had a renewed interest.

The Transition from "Percutaneous Nucleotomy"

It is ironic that in an era where endoscopic procedures were championed for their ability to provide direct visualization of anatomical structures in other subspecialties, the precursor to modern day endoscopic spine techniques was heralded by a "blind" nucleotomy or discectomy. Borrowing from principles from percutaneous biopsy of vertebral body lesions, (7-9) a technique for fluoroscopic-guided percutaneous non-visualized discectomy under local anesthesia was described by Parvis Kambin in 1973 (10) and Hijikata et al. (11) in 1975. Using specialized cannulas and instruments without endoscopic visualization, these techniques represented "intra-discal" indirect decompression procedures to address posterolateral disc hernations via removal of the posterior one third of the nucleus pulposus.

Using these techniques, Kambin and Schaffer (12) reported their results from a prospective series of 100 patients with 1- to 6-year follow-up with symptomatic lumbar herniations with unremitting radicular pain. They reported an 87% success rate based on a modified MacNab criteria, patient interview, examination, and questionnaire. Hijikata reported his results on 136 patients with 1- to 12-year follow-up using the Modified Japanese Orthopedic Association's score and found 72% of patients had good to excellent results. (13) Although it is difficult to decipher the meaning of these results as the percutaneous discectomy cohort had a narrow indication criteria and were not matched to any controls, these results were nonetheless promising and led to further interest in endoscopic techniques.

Kambin's Triangle

Early endoscopic spine surgery involved the extra-foraminal and neural foraminal area, resulting in extensive anatomical investigation. Kambin conducted numerous cadaveric studies to describe the boundaries of a safe working zone for posterolateral access to the disc space. (14,15) He defined Kambin's triangle, a theoretical right triangle over the posterolateral disc: the hypotenuse is the exiting nerve root, the base (width) is the superior border of the caudal vertebra, and the height is the dura and traversing nerve root. The triangle is loosely covered by adipose tissue and small superficial veins as well as suspensory ligaments tethering the neural structures. As surgeons gained comfort with this anatomical trajectory, the cannulas utilized for performing a discectomy increased in size to allow larger instruments to be passed through (16,17) and principles of arthroscopy were utilized to provide visualization of the procedure. (18) The first endoscopic views of a herniated nucleus pulposus were published by Kambin et al. (19) in 1988, and the first reported introduction of a modified arthroscope into the intervertebral disc space was reported by Forst and Hausman in 1983. (20) A prospective randomized study by Hermantin et al. (21) compared video-assisted arthroscopic microdiscectomy to traditional open microdiscectomy and found comparable outcomes with patients in the endoscopic cohort having higher satisfaction, shorter hospital stay, and less narcotic use postoperatively. Although a special working-channel endoscope, which allows instruments to be passed under visualization, was utilized, the procedure was predominantly intra-discal. The authors reported visualization of neural structures only after complete discectomy was performed with a separate 30[degrees] arthroscope. (21)

Transforaminal Technique

While the early procedures could be described as extraforaminal and disc-based, the transition of the endoscope into the foramen marked the beginning of the present-day trans-foraminal endoscopic discectomy. (22) In the late 1990s, Yeung designed the YESS endoscope, a 510k FDA approved multi-channel fluid integrated working channel rigid endoscope, to perform endoscopic transforaminal discectomy. (23) Yeung's technique borrowed from Kambin's arthroscopic discectomy technique (24) and Schreiber and Suezawa's use of injecting indigo carmine into the disc space to stain the abnormal nucleus pulposus and annular fissures. (25,26) The technique was primarily an intra-discal or "inside-out" procedure, however, Yeung described the use of lasers and other bone cutting instruments to perform a foraminoplasty to expand the foramen and improve visualization postdiscectomy. (23) By the mid 2000s, Schubert and Hoogland (27) described their technique for transforaminal endoscopic removal of a sequestered disc fragment using reamers to first expand the foraminal window by removing the ventral portion of the superior articular process. This was a philosophical shift returning to traditional spine surgery in which visualization was required prior to performing a discectomy. This marked the beginning of an "outside in" approach, which diverged from the earlier transforaminal techniques that were primarily intra-discal in nature.

Interlaminar Technique

While transforaminal endoscopic surgery was slowly evolving, the initial learning curve and lack of access to expert training resulted in slow adoption. Concurrently, the development of the tubular retractor system by Destandau (28) and Foley (29) in the late 1990s heralded a new era of minimally invasive techniques utilizing an interlaminar window. Although these techniques initially were endoscopically-assisted and resulted in other interlaminar endoscopic systems to be developed, (30) the use of the microscope soon supplanted the endoscope among most spine surgeons. However, with advancements in endoscopic technology and techniques, (31) endoscopic interlaminar approaches have been regaining popularity.

Current State of Endoscopic Spine Surgery

In the past 10 years, there has been an increasing focus on the power of endoscopic spine surgery with advances in techniques and technology. Currently available spinal endoscopes differ from traditional arthroscopes in that they have an additional working channel port to allow instruments to be passed under direct visualization (Fig. 1). Although endoscopic spine surgery initially centered around lumbar microdiscectomy for very limited contained disc herniations, pathology addressed has expanded to include virtually all types of disc herniations. Endoscopic techniques have been utilized for approaching pathology in the cervical, thoracic, and lumbar spine. (32-34) Endoscopic decompressions have been utilized in the settings of degenerative spinal stenosis, spondylolisthesis, scoliosis, previous fusion, (35) tumor, (36) and infection. (37) Furthermore, endoscopic interbody fusion has also been utilized in the lumbar spine (38,39) as technology continues to advance. As technological innovation continues to facilitate reproducible surgical technique, endoscopic spine surgery will continue to increase in popularity among surgeons and patients alike.

Lumbar Surgery

Transforaminal Techniques

Kambin's triangle, the medial aspect of the foraminal annular window bordered by the exiting root rostrally, the traversing root medially, and the superior endplate of the lower lumbar vertebra inferiorly, is the primary anatomic basis for procedures utilizing this approach (Fig. 2). This approach can allow undercutting of the facet joint (ventral facetectomy), discectomy, mobilization, neurolysis of the exiting and traversing nerve roots, and ablation of osteophytes. Utilizing a transforaminal trajectory has been shown to be biomechanicically more disruptive than a traditional posterior approach. Osman et al. (40) conducted a cadaveric study comparing tranforaminal versus posterior ipsilateral medial facetectomy and found the transforaminal technique resulted in a 45% increase in the foraminal area, while the posterior approach resulted in 34% increase in the foraminal area (p < 0.001). (40) Furthermore, the posterior approach resulted in increased instability in extension and axial rotation, while the transforaminal resulted in no measurable instability. A foraminotomy, discectomy, and lateral recess decompression can all be accomplished using the transforaminal trajectory. Essential to the transforaminal technique is a thorough understanding of the pathology that is being addressed; given the targeted nature of the endoscope, approach angles and skin entry points must be precise to ensure efficient work flow.

Ahn conducted a prospective study to investigate the clinical outcomes of 33 consecutive patients who underwent endoscopic trans-foraminal decompression for lumbar foraminal stenosis. There were significant improvements in the mean VAS-leg (8.36 to 1.9) and ODI scores (65.3 to 19.3) at 2-years postoperatively with good to excellent results per the MacNab criteria obtained in 81.8% of the patients. (41) A recent cadaveric study demonstrated that the transforaminal approach combined with an extensive foraminoplasty allows for access to the lateral recess both ventral as well as dorsal to the traversing nerve root. (42) Thus yellow ligament and SAP dorsal to the traversing nerve root can be removed, which the authors referred to as a "ventral facectomy." A retrospective case series of 48 patients reporteds on transforaminal decompression of foraminal or lateral recess stenosis in patients with previous spinal surgery (43) and demonstrated "excellent" or "good" results according to MacNab criteria in 79% of patients with a minimum of 2-years follow-up.

There are numerous randomized controlled and prospective studies that investigate clinical outcomes following full endoscopic transforaminal microdiscectomy. Ruetten et al. (32) conducted a prospective controlled study of 200 patients who were randomized to either full-endoscopic discectomy (transforaminal or interlaminar) or open microsurgical discectomy with 2-year follow-up. Both groups experienced similar improvements in pain and function, however, a statistically significant number of patients in the microsurgical group experienced greater back pain postoperatively. There were no significant differences in reoperation rates between the two groups, however, the endoscopic cohort was found to have statistically significant fewer complications, lower postoperative pain medication requirements, and less postoperative work disability. Similarly, Gibson et al. (44) conducted a prospective randomized controlled study of 140 patients who underwent endoscopic transforaminal discectomies or open microsurgical discectomy with 2-year follow-up available on 123 patients. While both cohorts noted significant improvement from baseline, VAS leg pain scores at 2 years were significantly less following endoscopic discectomy (1.9 [+ or -] 2.6) when compared to microsurgical discectomy (3.5 [+ or -] 3.1, p = 0.002). There was no significant difference in reoperation and complication rates between the cohorts, however, the endoscopic group was found to have a significantly shorter length of hospital stay.

Interlaminar Techniques

Interlaminar techniques utilize familiar anatomy to traditional open and MIS-tubular spine surgery. Using an endoscope, the standard interlaminar window can be used to decompress central, lateral, and foraminal stenosis (Fig. 3). Some technical advantages of utilizing an endoscope for interlaminar decompression include preservation of the bony anatomy of the ipsilateral and contralateral facet joints due to the maneuverability and visualization afforded by the endoscope. This is due to the relatively narrow size of currently available endoscopes (6 to10 mm) as well as a wide and dynamic field of view, which allows trajectories that would otherwise be obfuscated by line of sight limitations from a microscope and tubular retractors.

Minimally invasive techniques such as tubular unilateral laminotomy for bilateral decompression (ULBD) have been shown to provide comparable outcomes with open techniques with less overall morbidity. (45,46) In a prospective randomized controlled trial of 79 patients undergoing tubular ULBD versus open laminectomy for lumbar spinal stenosis (LSS) with average 3-year follow-up, the minimally invasive alternative was shown to have overall equivalent patient reported outcomes to open laminectomy with shorter hospital stay, less blood loss, and lower opioid pain requirements. (47) Endoscopic spine surgery represents the evolution of these tubular minimally invasive techniques; the advantage of full-endoscopic surgery include a small working corridor with minimal irritation of the paraspinal muscles, constant irrigation which provides a clear operative field, and gentle general retraction of the thecal sac and nerve roots as well as an angled view resulting in the ability to effectively undercut the fact joint.

These advantages are particularly important in patients with lumbar spinal stenosis and concomitant structural pathology such as degenerative spondylolisthesis and scoliosis. In current surgical practice, fusion is the treatment of choice for patients with LSS associated with degenerative spondylolisthesis and scoliosis. (48) In the United States, 96% of patients with degenerative spondylolisthesis undergo fusion surgery as an adjunct to decompression, (49) and approximately 70% of patients with LSS and coexisting scoliosis undergo a fusion procedure. (50) A large analysis of registry data showed that the addition of fusion surgery to decompression surgery for spinal stenosis doubled the risk of severe adverse events. (51,52) The potential risks and complications are significantly amplified when the alternative to decompression includes long construct fusions, with some series showing complication rates greater than 50%. (53) These studies highlight the controversy surrounding the role of conventional laminectomy and potential iatrogenic instability in LSS patients with structural pathology with reported reoperation rates of 25% to 37%. (54,55) Minamide et al. (56) recently reported on 242 patients with spinal stenosis and degenerative spondylolisthesis who underwent microendoscopic (endoscopic-assisted tubular) ULBD with a mean 4.6-year follow-up. They reported excellent to good recovery of JOA score in approximately 70% of patients and a reoperation rate of 7.8%, with only 5% of patients requiring fusion at last follow-up. Interestingly, based on radiographic analysis, the rate of progressive instability was 7.8% with restabilization of the spine in 35% of patients with preoperative instability. Notably, there was an overall complication rate of 4.5% that included a 1.2% rate of dural tears, a 1.7% rate of epidural hematomas, and a 0.4% infection rate.

A recent retrospective analysis of 95 consecutive patients undergoing either minimally-invasive tubular (N = 45) versus endoscopic (N = 50) unilateral laminotomies for bilateral decompression for lumbar spinal stenosis found the endoscopic cohort to have better clinical VAS-leg scores (1.3 [+ or -] 0.3 vs. 3.0 [+ or -] 0.5; p < 0.01) and ODI scores (20.7 [+ or -] 3.4 vs. 35.9 [+ or -] 4.1; p < 0.01) at 1-year follow-up. Furthermore, the endoscopic cohort was found to have a shorter hospital stay (0.7 [+ or -] 0.1 days vs. 2.4 [+ or -] 0.5 days; p < 0.001), less complications (8.0% vs. 26.7%; p < 0.05), and fewer reoperations (6.0% vs. 6.67%; p > 0.05). (57) When looking at a subgroup of patients with degenerative spondylolisthesis and degenerative scoliosis, no patients in the endoscopic cohort required reoperation within the 1-year follow-up period. While larger studies are needed to further understand the role of endoscopic spine surgery in this patient population, the current available data remains promising.

Thoracic Surgery

The use of endoscopic techniques in the thoracic spine are particularly advantageous when addressing thoracic disc herniations with ventral compression of the spinal cord (Fig. 4). This clinical scenario represents a challenging problem for many spine surgeons. Current accepted approaches include posterolateral costotransversectomy, (58) posterior transpedicular, (59) lateral extracavitary, (60) transthoracic, (61) and video-assisted thorascopic (VATS). (62) Many of these approaches require significant soft tissue stripping and extensive bone resection or require entrance into the thoracic and pleural cavities with its associated morbidity. Fessler and Sturgill (63) reviewed reported complications following various approaches to address thoracic disc herniations and found that in 242 patients, approximately 26% of procedures were associated with significant morbidity and mortality. These procedures, whether intrapleural or retropleural, can result in significant perioperative morbidity secondary to pain, difficult ventilation requiring prolonged ICU stay, shoulder girdle dysfunction, and wound healing problems. (64,65) Even more minimally-invasive thoracoscopic methods such as VATS have complication rates reported to be up to 21%. (62) The endoscopic transforaminal approach offers the ability to safely access thoracic disc herniations with minimal bony and soft tissue disruption while avoiding entrance into the thoracic cavity. Choi et al. (66) reported on 14 patients with a soft thoracic disc herniation who underwent endoscopic transforaminal thoracic discectomy with an average 5-year follow-up. There were significant improvements in VAS and ODI from baseline, no surgery-related complications were observed, and no conversions to an open procedure were required. Similarly, Nie and Liu (34) reported 77% excellent to good results for 13 patients who underwent endoscopic transforaminal thoracic discectomy with average 17-month follow-up. They reported a 0.08% complication rate with one dural tear treated successfully with a blood patch. Although evidence for endoscopic techniques in the thoracic spine are currently limited to case series and will require more investigation, the current available data remains promising.

Cervical Surgery

Currently applications of endoscopic spine surgery to treat cervical pathology include posterior cervical foraminotomy (PCF), posterior cervical laminectomy, and anterior discectomy. Endoscopic PCF foraminotomy can be used to address a lateral disc herniation and osseous foraminal stenosis with far less muscle dissection and bony resection than open techniques (67,68) (Fig. 5). When comparing traditional anterior cervical decompression and fusion (ACDF) to open PCF for the treatment of soft lateral disc herniations, the literature has shown that both techniques have similar outcomes, complication profiles, and index-level reoperation rates, (69-74) with PCF being shown to be more cost-effective over ACDF. (75,76) Given the motion-preserving nature of PCF, the reoperation rate for adjacent segment disease is substantially more common after a fusion procedure, occurring in approximately 12% of patients undergoing ACDF77 and only 2% to 3% after cervical foraminotomy. (73)

However, a traditional open PCF entails significant stripping of the posterior cervical musculature with painful postoperative recovery, potential wound complications, and risk of postoperative kyphosis. (71,78) Minimally invasive techniques provide for comparable results with less blood loss, lower pain management requirements, faster recovery, and shorter hospital stay over the standard open technique. (79-81) Ruetten et al. (33) conducted a prospective randomized controlled trial of 175 patients who underwent endoscopic PCF or ACDF with 2-year follow-up. The authors reported equivalent functional outcomes in both groups with no significant differences in the reoperation rate or number of overall complications. Notably, postoperative pain and postoperative work disability was significantly less in the endoscopic PCF group, and the 3% complication rate in this cohort was limited to transient hypesthesia; furthermore, there was no radiographic evidence of increasing kyphosis or instability. Due to the maneuverability of the endoscope and the ability to manipulate optical field of view, we believe endoscopic PCF allows for a more thorough decompression of the cervical nerve root beyond the pedicle with minimal bony resection.

Similarly, minimally-invasive techniques have been shown to be valuable in the treatment of cervical myelopathy with the goal of performing a decompression procedure while minimizing the risk of post-laminectomy kyphosis. (82) Minamide et al. (56) recently compared 5-year clinical and radiologic outcomes following 78 patients who underwent either cervical endoscopically-assisted tubular laminotomy or conventional expansive laminoplasty and found similar JOA recovery rates and complication rates with significantly less blood loss, post-inflammatory markers, and postoperative neck pain in the microendoscopic group. The most notable findings from this study is that the microendoscopic group not only had a lower incidence of postoperative kyphosis, but there was a statistically significant greater gain in lordosis (+2.6[degrees]) when compared to the laminoplasty group (-1.2[degrees]), (p = 0.031). Although there has been only one small case series reporting on outcomes following full-endoscopic decompression of patients with cervical myelopathy, the author reported favorable outcomes with no perioperative complications. (83) Although other endoscopic cervical techniques including anterior cervical discectomy for disc herniation (84,85) and microendoscopic laminoplasty (86) have been reported, there is currently limited data regarding long-term outcomes and complication profiles.

Complications Profile

Although endoscopic spine surgery enjoys growing popularity in Asia and Europe, the United States has lagged in widespread adoption. General unfamiliarity with the nature of endoscopic procedures, limited access to learning opportunities, and fear for catastrophic complications are some of reasons many spine surgeons have not embraced endoscopic techniques when treating spinal pathology. When looking at the compendium of literature on the use of current endoscopic techniques, endoscopic spine surgery not only provides equivalent outcomes with faster recovery but is also safer than current open techniques.

When comparing the complication profiles of open versus endoscopic treatment of lumbar disc herniation and lumbar spinal stenosis, endoscopic techniques have been shown to have a more favorable risk profile with equivalent to superior clinical outcomes. When looking at data from the randomized controlled Spine Outcomes Research Trial (SPORT) for microsurgical discectomy versus non-operative treatment of lumbar disc herniation, the average reoperation rate was 7.4% at 1 year and 10.2% at 2 years (87); furthermore, the authors reported an overall 20.9% complication rate (including reoperations) with a 4.1% incidence of incidental durotomies and a 1.6% infection rate. An analysis of an aggregate of 540 patients who underwent endoscopic discectomy from five randomized controlled and prospective studies with 1- to 2-year follow-up (32,44,88-90) found an average reoperation rate of 6.5%, a 10.5% overall complication rate (including all perioperative complications and reoperations), and equivalent to superior clinical outcomes. Furthermore, there was an overall 0.3% incidence of incidental durotomy and infection in these studies.

When looking at two recent landmark prospective randomized controlled trials comparing open laminectomy versus fusion for patients with lumbar spinal stenosis in the setting of stable degenerative spondylolisthesis, open laminectomy was associated with significant morbidity. (91,92) Forsth et al. (92) reported a 21% reoperation rate, an 11% rate of dural tears, a 4% infection rate, and a 4% rate of other postoperative medical complications. Ghogawala et al. (91) reported a 34% reoperation rate and a 6% rate of major complications. When looking at the SPORT trial for the treatment of patients with spinal stenosis without spondylolisthesis, (93) the rate of reoperation at 4 years was 13%, the rate of dural tears was 10%, the rate of infection was 3%, the rate of postoperative transfusion was 5%, and the rate of all perioperative complications (not including reoperation) was 18%. When looking at these prospective randomized controlled trials, the overall complication rate (including reoperation) for both open laminectomy and fusion ranged from 37% to 45%. (91-93) Comparatively, the current available literature for endoscopic treatment of spinal stenosis has shown reoperation rates of 6% to 8% with overall complication rates ranging from 4.5% to 8%. (56,57) Although there is currently a paucity of literature utilizing endoscopic techniques for the treatment of thoracic and cervical procedures, current available research indicates that endoscopic techniques can be used to effectively and safely treat thoracic (94,95) and cervical pathology. (96-100)

Future Direction

As endoscopic spine surgery continues to enjoy wider adoption, spine surgeons are expanding potential indications for use of this technology. Numerous case series have shown potential applications in patients with complex pathology including burst fractures, (101) BMP related heterotopic ossification, (35,102) synovial cysts, (103,104) migrated hardware, (35) discitis, (37) spinal cord untethering, (105) and tumors. (36) Surgical innovation has resulted in the utilization of bi-portal techniques, (106-108) the use of navigation to provide more precise targeting of spinal pathology (109-111) as well as the use of endoscopy to perform interbody fusions. (112-114) Further technological innovation may combine robotic, (115) augmented reality, (116) and endoscopic technologies providing for limitless possibilities with the potential to revolutionize the field of spine surgery.

Conclusion

Endoscopic spine surgery has seen over 30 years of evolution, and much has been learned from early iterations of these procedures. We believe that in the context of embracing new technologies, spine surgeons are now beginning to understand the role for the use of endoscopic techniques in spine surgery. The true utility in the treatment of spinal pathology lies in providing a less invasive but effective treatment alternative with a more favorable risk profile than current open techniques. Although there is a learning curve associated with these procedures, we believe that endoscopic techniques offer a more powerful and less morbid approach to spinal pathology that ultimately elevates the standard of care when treating our patients.

Disclosure Statement

None of the authors have a financial or proprietary interest in the subject matter or materials discussed in the manuscript, including, but not limited to, employment, consultancies, stock ownership, honoraria, and paid expert testimony.

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Saqib Hasan, MD, and Christoph P. Hofstetter, MD, PhD

Saqib Hasan, MD, Department of Orthopedic Surgery, and Christoph P. Hofstetter, MD, PhD, Department of Neurological Surgery, The University of Washington, Seattle, Washington, USA.

Correspondence: Saqib Hasan, MD, Department of Orthopedic Surgery, The University of Washington, Campus Box 356470, Room RR734, 1959 NE Pacific Street, Seattle, Washington, 98195-6470, USA; saqibhasanmd@gmail.com.

Caption: Figure 1 A, A typical working channel endoscope utilized in endoscopic spine surgery. The tip of the endoscope is typically beveled with the camera port positioned at a variable angle (0[degrees], 15[degrees], and 30[degrees]). The tip of the endoscope will also have ports for a light source, irrigation channel, and a working channel through which instruments can be passed under direct visualization. B, The wide dynamic panoramic view that can be obtained with the via rotation of the endoscope. To view this figure in color, see www.hjdbulletin.org.

Caption: Figure 2 A, The typical axial trajectory for the transforaminal approach. The trajectory is planned preoperatively using an axial MRI and an estimation of the skin entry point can be made. B, An endoscope positioned in Kambin's triangle and the anatomical structures that are visible via this approach. SAP represents the superior articular process of the caudal vertebrae. To view this figure in color, see www.hjdbulletin.org.

Caption: Figure 3 A, The lumbar interlaminar window and endoscopic images following creation of an ipsilateral unilateral laminotomy with an endoscopic burr (left image), followed by removal of the ligamentum flavum to visualize the ipsilateral traversing nerve root. B, The interlaminar window with the endoscope rotated to provide an endoscopic image of the contralateral traversing nerve root following contralateral extension of the laminotomy and removal of the ligamentum flavum. IAP represents the inferior articular process, SP represents the spinous process, LF represents the ligamentum flavum, TNR represents the traversing nerve root. The R on the compass represents rostral, and the C represents caudal. To view this figure in color, see www.hjdbulletin.org.

Caption: Figure 4 A, A transforaminal endoscopic image of a T12-L1 paracentral soft disc herniation. B, An endoscopic image following foraminoplasty and removal of the herniated disc. SAP represents the superior articular process of the caudal vertebrae, HNP represented the herniated nucleus pulposus fragment, CORD represents the spinal cord. The R on the compass represents rostral, and the C represents caudal. To view this figure in color, see www.hjdbulletin.org.

Caption: Figure 5 The cervical interlaminar window and an endoscopic image following full-endoscopic right-sided foraminotomy of the C4-C5 level. The maneuverability and optical viewing angle allows for the ability to visualize and easily undercut the superior articular process. The star on the left of the endoscopic image is the spinal cord. The decompressed C5 nerve root (star on the right side of the endoscopic image) has been decompressed passed the rostral pedicle (P). A disc fragment was removed from the disc space (D) in the axilla of the nerve root. The R on the compass represents rostral, and the C represents caudal. To view this figure in color, see www.hjdbulletin.org.

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Author:Hasan, Saqib; Hofstetter, Christoph P.
Publication:Bulletin of the NYU Hospital for Joint Diseases
Article Type:Medical procedure overview
Date:Jan 1, 2019
Words:7966
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