Faculty Bibliography

OBJECTIVE The authors describe a cadaveric analysis to determine the ideal dimensions and trajectory for considering endoscopic transforaminal interbody implantation. METHODS The soft tissues of 8 human cadavers were removed from L-1 to the sacrum, exposing the posterior bony elements. Facetectomies were performed bilaterally at each lumbar level with resection of the pars interarticularis, revealing the pedicles, nerve roots, and interbody disc space. Each level was digitally photographed with a marker for scale and evaluated with digital analysis software. The traversing and exiting nerve roots and pedicle margins were identified, and the distances between these structures and their relationships to the surrounding structures were documented. RESULTS The dimensions of 2 areas were measured: the working triangle and safe zone. The working triangle is the triangle between the exiting and traversing nerve roots above the superior margin of the inferior pedicle. The safe zone is the trapezoid bounded by the widths of the superior and inferior pedicles between the exiting and traversing nerve roots. The mean surface area for the working triangle was 1.83 cm(2), with L5-S1 having the largest area at 2.19 cm(2). The mean surface area of the safe zone was 1.19 cm(2), with L5-S1 having the largest area at 1.26 cm(2). At the medial border of the pedicle extending superiorly, there were no nerve structures within 1.19 cm at any level. On the lateral border of the pedicle, the exiting nerve root was closer superiorly, with the closest being 0.3 cm. CONCLUSIONS The working triangle is a relatively large area. The safe zone, just superior to the pedicle, is free of nerve structures. By utilizing the superior border of the pedicle, the disc space can be accessed within this safe zone without risk of injury to the nerves. A thorough understanding of foraminal anatomy is fundamental for considering how to safely access the disc space, thereby utilizing less invasive endoscopic techniques, and is an important first step in considering what shapes and sizes of interbody implants and retractors are feasible for use in the foramen.

Few neurosurgeons practicing today have had training in the field of endoscopic spine surgery during residency or fellowship. Nevertheless, over the past 40 years individual spine surgeons from around the world have worked to create a subfield of minimally invasive spine surgery that takes the point of visualization away from the surgeon's eye or the lens of a microscope and puts it directly at the point of spine pathology. What follows is an attempt to describe the story of how endoscopic spine surgery developed and to credit some of those who have been the biggest contributors to its development.

OBJECTIVE The aim of this study was to describe patient radiation exposure during single-level transforaminal endoscopic lumbar discectomy procedures at levels L2-5 and L5-S1. METHODS Radiation exposure was monitored in 151 consecutive patients undergoing single-level transforaminal endoscopic lumbar discectomy procedures. Two groups were studied: patients undergoing procedures at the L4-5 level or above and those undergoing an L5-S1 procedure. RESULTS For the discectomy procedures at L4-5 and above, the average duration of fluoroscopy was 38.4 seconds and the mean calculated patient radiation exposure dose was 1.5 mSv. For the L5-S1 procedures, average fluoroscopy time was 54.6 seconds and the mean calculated radiation exposure dose was 2.1 mSv. The average patient radiation exposure dose among these cases represents a 3.5-fold decrease compared with the senior surgeon's first 100 cases. CONCLUSIONS Transforaminal lumbar endoscopic discectomy can be used as a minimally invasive technique for the treatment of lumbar radiculopathy in the setting of a herniated lumbar disc without the significant concern of exposing the patient to harmful doses of radiation. One caveat is that both the surgeon and the patient are likely to be exposed to higher doses of radiation during a surgeon's early experience in minimally invasive endoscopic spine surgery.

The proposed advantages of total disc replacement (TDR) over fusion in the lumbar spine are the preservation of motion and the avoidance of adjacent-level disease. One of the complications inherent in TDR is the possibility of vertebral body fracture due to trauma or a malpositioned implant. The resulting dilemma is that posterior decompression of the displaced bone fragment could then have a destabilizing effect and possibly require fusion, thus obviating the benefit of an arthroplasty procedure. In this study, the authors describe the technical considerations and feasibility of the treatment of a postoperative L-5 paresis that resulted from a dislocated bone fragment at L4-5 during a 2-level lumbar TDR.

OBJECTIVE In this study the authors describe the technical considerations and feasibility of transforaminal discectomy and foraminoplasty for the treatment of lumbar radiculopathy in patients who have herniated discs at the thoracolumbar junction. METHODS After institutional review board approval, charts from 3 consecutive patients with lumbar radiculopathy and T12-L1 herniated discs who underwent endoscopic procedures between 2006 and 2014 were reviewed. RESULTS Consecutive cases (n = 1316) were reviewed to determine the incidence and success of surgery performed at the T12-L1 level. Only 3 patients (0.23%) treated with endoscopic surgery for their herniated discs had T12-L1 herniated discs; the rest were lumbar or lumbosacral herniations. For patients with T12-L1 disc herniations, the average preoperative visual analog scale score was 8.3 (indicated in the questionnaire as describing severe and constant pain). The average 1-year postoperative visual analog scale score was 1.7 (indicated in the questionnaire as mild and intermittent pain). CONCLUSIONS Transforaminal endoscopic discectomy and foraminotomy can be used as a safe yet minimally invasive technique for the treatment of lumbar radiculopathy in the setting of a thoracolumbar disc herniation.

Transforaminal endoscopic spine surgery has emerged internationally as a minimally invasive technique that can be performed in an awake patient in the outpatient setting. Advances in high-definition endoscopic camera technologies as well as the availability of specialty graspers, reamers, drills, and other instruments that can be used down a working channel endoscope have made a myriad of spine diseases accessible to the minimally invasive spine surgeon. The major challenge inherent in the surgical treatment of thoracic disc disease is that the disc herniation is often ventral to the spinal cord. The transforaminal approach and the angled endoscopic camera are an ideal combination for creating a technical advantage to accessing thoracic disc disease.

Kyphoplasty is a minimally invasive spine surgical procedure performed to stabilize and treat the pain caused by a spine compression fracture. Complications are rare with kyphoplasty and include cement extrusion into the vertebral canal leading to spinal cord or nerve root compression. Herein, the authors present a case of a 72-year-old woman who presented with symptoms of a right L2 radiculopathy after a kyphoplasty procedure. Computed tomography imaging showed leakage of the kyphoplasty cement into the neural foramen above and medial to the right L2 pedicle. A transforaminal endoscopic surgical approach was used to remove the cement and decompress the L2 nerve. The patient's postoperative clinical course was uneventful. Clinicians should be aware that for the treatment of complications to vertebroplasty and kyphoplasty procedures, minimally invasive transforaminal endoscopic surgery is one option to avoid the destabilizing effects of laminectomy and facetectomy.

OBJECTIVE:Endoscopic surgery for highly migrated lumbar disk extrusions is a challenge even for spine surgeons who are familiar with using endoscopic techniques. Because of the anatomic constraints involved in transforaminal access in endoscopic surgery, an incomplete removal of a highly migrated disk extrusion can result in some cases. Here the authors describe a new technique for accessing extruded lumbar disks that have migrated into the canal directly through a transpedicular approach. METHODS:A technique for the endoscopic treatment of highly migrated lumbar disk extrusions is presented. Retrospectively, we reviewed a series of 21 consecutive patients operated on with lumbar 3-4, lumbar 4-5, and lumbar 5-sacral 1 highly migrated disk extrusions: preoperative and postoperative clinical data with 1-year follow-up. RESULTS:A preliminary series of 11 male and 10 female patients with an average age of 56.9 years (from 33-78 years old) who underwent transpedicular endoscopic retrieval of an extruded lumbar disk between 2012 and 2015 is presented. Two patients required revision to transforaminal access, 1 at the same sitting and the other 4 weeks later. The mean visual analog scale score for radicular pain improved from an average pain score before surgery of 8.1-1.7 one year after surgery. No pedicle fractures were encountered. CONCLUSIONS:Transpedicular endoscopic access to highly migrated lumbar herniated disk extrusions is presented as a unique minimally invasive approach to extruded lumbar herniated disks, especially at L3-4, L4-5, and L5-S1.

BACKGROUND:Lumbar facet cysts are a benign, degenerative, and fairly uncommon cause for lumbar radiculopathy. The standard surgical treatment for lumbar facet cysts often requires a laminectomy and medial facetectomy which can further destabilize a pathological motion segment. The authors present here a novel technique for transpedicular endoscopic access to the pathology that obviates the need to violate the lamina or facet. METHODS:Two patient cases are described where the lumbar 4-5 facet cysts arise medial to the pedicle. Percutaneous access to the cysts was established by drilling through the adjacent pedicle creating a 7-mm corridor to establish access for the endoscopic tubular retractor and the working channel endoscope. Straight and bendable forceps were used to remove the cysts under direct visualization. RESULTS:Following surgery, the patients' symptoms showed immediate regression with complete relief of one patient's foot drop by 6 months. CONCLUSIONS:Transpedicular endoscopic access is described as novel minimally invasive surgical option in the awake patient for lumbar facet cysts adjacent to the Lumbar 4 or 5 pedicle.