Faculty Bibliography

Total uncinate process resection or uncinectomy is often required in the setting of severe foraminal stenosis or cervical kyphosis correction. The proximity of the uncus to the vertebral artery, nerve root, and spinal cord makes this a challenging undertaking. Use of a high-speed burr or ultrasonic bone dissector can be associated with direct injury to the vertebral artery and thermal injury to the surrounding structures. The use of an osteotome is a safe and efficient method of uncinectomy. Here the authors describe their technique, which is illustrated with an intraoperative video.

BACKGROUND:Idiopathic spinal cord herniation is a disorder in which the spinal cord herniates through a dural defect. We present a case in which both the standard surgical method and a salvage method failed. CASE DESCRIPTION/METHODS:A 36 year-old man presented with two years of progressive numbness and proximal hip flexion weakness of both lower extremities. MRI of the thoracic spine was suggestive for a ventral spinal cord herniation at the T6/7 level. He was initially treated with reduction of his cord herniation, placement of a ventral sling of collagen matrix over the dural defect to prevent re-herniation, with a laminoplasty. He developed a blood-pressure-dependent paraparesis that did not recover despite a return to the OR for removal of the laminoplastic bone flap. He was again taken to the OR, the sling was removed and we enlarged the ventral dural defect rostrally and caudally to prevent strangulation of the hernia as described by Watanabe. Though in the short term he was able to recover and transfer to physical therapy, after going home he developed lower extremity weakness and low-pressure headaches. MRI showed a ventral epidural CSF pocket retropulsing the spinal cord, as well as pockets of ventral CSF collections remote from the surgery site. The patient returned to the OR and the initial surgery with the ventral sling was re-performed with resolution of the headaches and was neurologically stable and transferred to rehab. Long-term he developed left intercostal pain at the level of the surgery without radiological correlate. CONCLUSION/CONCLUSIONS:In this patient there was no single satisfactory surgical treatment of his ventrally herniated spinal cord - partly related to the herniated component of the cord acting as a mass within a narrow canal at the apex of the thoracic kyphosis. We encountered previously unreported complications of the ventral defect widening technique of surgical treatment.

STUDY DESIGN/METHODS:This is a retrospective analysis of electromyographic (EMG) stimulation thresholds of 64 cortical bone trajectory (CBT) screws. OBJECTIVE:The authors seek to determine whether recordings below stimulation threshold correlate with CBT screw pedicle breach on computed tomographic imaging, and to explore which specific nerve roots are most at risk with this new trajectory. SUMMARY OF BACKGROUND DATA/BACKGROUND:Intraoperative EMG monitoring has been utilized to verify accurate placement of pedicle screws. Although CBT screws are becoming increasingly popular, to the authors' knowledge there are no existing evaluations of the accuracy of intraoperative triggered EMG (tEMG) monitoring in this trajectory. MATERIALS AND METHODS/METHODS:Retrospective analysis of EMG stimulation thresholds of 64 CBT screws placed in patients at NYU Langone Medical Center from 2015-2017. EMG results including threshold values and muscle group stimulated were correlated with screw positioning determined on postoperative or intraoperative computed tomographic imaging. RESULTS:In total, 4.7% of EMG threshold values indicated true breach, 1.6% were falsely positive for breach, 76.5% showed true absence of breach, 17.1% failed to reveal a present breach though 0% of medial breaches were undetected. L4 screws showed tEMG responses from adductor longus in 22%, L5 screws, from rectus femoris in 16.7%, and S1 screws from tibialis anterior in 50%. CONCLUSIONS:tEMG testing is effective for medial breaches in CBT screws. In addition, there is evidence that bicortical placement of these screws causes lower stimulation values due to distal breach. Importantly, it seems that this is due in part to stimulation of the exiting nerve root at the level above.

Spinal cord compression due to synovial facet cyst in thoracolumbar spine is rare. Several etiologies of juxtafacet cysts (JFCs) in this location have been discussed, particularly overload of the arthritic facet joints. Due to the narrow caliber of the thoracic spine, JFC in this location can present with radicular pain or progressive myelopathy. We report an interesting case of a 67 year-old woman who presented with the signs and symptoms of thoracic myelopathy. A left-sided T11/12 JFC was identified on MRI and CT scans correlating with her myelopathy. She experienced a substantial improvement in her myelopathic symptoms after surgical excision of the JFC. The presentation, etiology, and therapeutic aspects of JFC are discussed in detail.

OBJECTIVE Off-label therapies are widely used in clinical practice by spinal surgeons. Some patients and practitioners have advocated for increased regulation of their use, and payers have increasingly questioned reimbursment for off-label therapies. In this study, the authors applied a model that quantifies publication data to analyze the developmental process from initial on-label use to off-label innovation, using as an example recombinant human bone morphogenetic protein 2 (rhBMP-2) because of its wide off-label use. METHODS As a case study of off-label innovation, the developmental patterns of rhBMP-2 from FDA-approved use for anterior lumbar interbody fusion to several of its off-label uses, including posterolateral lumbar fusion, anterior cervical discectomy and fusion, and posterior lumbar interbody fusion/transforaminal lumbar interbody fusion, were evaluated using the "progressive scholarly acceptance" (PSA) model. In this model, PSA is used as an end point indicating acceptance of a therapy or procedure by the relevant scientific community and is reached when the total number of peer-reviewed studies devoted to refinement or improvement of a therapy surpasses the total number assessing initial efficacy. Report characteristics, including the number of patients studied and study design, were assessed in addition to the time to and pattern of community acceptance, and results compared with previous developmental study findings. Disclosures and reported conflicts of interest for all articles were reviewed, and these data were also used in the analysis. RESULTS Publication data indicated that the acceptance of rhBMP-2 off-label therapies occurred more rapidly and with less evidence than previously studied on-label therapies. Additionally, the community appeared to respond more robustly (by rapidly changing publication patterns) to reports of adverse events than to new questions of efficacy. CONCLUSIONS The development of off-label therapies, including the influence of investigative methods, regulation, and changing perspectives, can be characterized on the basis of publication patterns. The approach and findings in this report could inform future off-label development of therapies and procedures as well as attempts to regulate off-label use.

INTRODUCTION: Rigid fixation of the atlantoaxial joint can be quite challenging due to complex anatomic variants. Numerous techniques have evolved over time, improving the surgeon's adaptability. The recent advent of C2 laminar screws adds to the surgeon's armamentarium, but is not without its own set of limitations. Risk of ventral laminar breach with possible spinal cord injury, CSF leak, or poor bony fixation have led some to recommend prefabricated models or expensive intraoperative spinal navigation to aid screw placement. The purpose of this report is to detail how the use of intraoperative fluoroscopy can be used to aid in the safe placement of C2 laminar screws. METHODS: One patient with rheumatoid arthritis and progressive cervical myelopathy from C1-2 instability underwent C1-2 fixation using C2 laminar screws. Intraoperative fluoroscopy was used to guide and confirm safe laminar screw placement. RESULTS: Immediate and 6-month postoperative imaging demonstrated excellent placement of C2 laminar screws without ventral breach. At 6 months, the patient noted significant improvement of her preoperative symptoms. CONCLUSION: Use of intraoperative fluoroscopy is an easy and safe method for the placement of C2 laminar screws. Given its use of readily available equipment, this method can be implemented without significant pre-planning, or as an impromptu salvage maneuver.

STUDY DESIGN:: Structured review of literature and application of meta-analysis statistical techniques. OBJECTIVE:: Review published series describing clinical and radiographic outcomes of patients treated with C1 lateral mass screws (C1LMS), specifically analyzing the impact of starting point and bicortical purchase on successful atlantoaxial arthrodesis. SUMMARY OF BACKGROUND DATA:: Biomechanical studies suggest posterior arch screws and C1LMS with bicortical purchase are stronger than screws placed within the center of the lateral mass or those with unicortical purchase. METHODS:: Online databases were searched for English-language articles between 1994 and 2012 describing posterior atlantal instrumentation with C1LMS. Thirty-four studies describing 1247 patients having posterior atlantoaxial fusion with C1LMS met inclusion criteria. RESULTS:: All studies provided Class III evidence. Arthrodesis was quite successful regardless of technique (~99.0% overall). Meta-analysis and multivariate regression analyses showed that neither posterior arch starting point nor bicortical screw purchase translated into a higher rate of successful arthrodesis. There were no complications from bicortical screw purchase. CONCLUSIONS:: The Goel-Harms technique is a very safe and successful technique for achieving atlantoaxial fusion, regardless of minor variations in C1LMS technique. Although biomechanical studies suggest markedly increased rigidity of bicortical and posterior arch C1LMS, the significance of these findings may be minimal in the clinical setting of atlantoaxial fixation and fusion with modern techniques. The decision to use either technique must be made after careful review of the preoperative multiplanar CT imaging, assessment of the unique anatomy of each patient and the demands of the clinical scenario such as bone quality.

STUDY DESIGN:: Literature review and meta-analysis. OBJECTIVE:: To compare clinical and radiographic outcomes of patients treated with C1 lateral mass screws (C1LMS), analyzing the impact of screw starting point and C2 nerve sectioning on malposition, vertebral artery injury (VAI) and C2 neuralgia and numbness. BACKGROUND:: Various starting points have been suggested for C1LMS insertion. Some advocate sectioning the C2 nerve root to ease placement. METHODS:: Online databases were searched for English-language articles between 1994 and 2012 reporting on C1LMS. Forty-two studies describing 1471 patients instrumented with 2905 C1LMS met inclusion criteria. Three surgical techniques included posterior arch starting point and center of lateral mass with nerve root preservation or sacrifice. RESULTS:: All studies provided Class III evidence. Three injuries to the vertebral artery occurred secondary to C1LMS insertion (0.1%) and 5 instances of clinically significant screw malpositions (0.2%). Postoperative imaging revealed 45 malpositioned screws (1.6%) without clinical consequences. Meta-analysis techniques demonstrated that sacrifice of the C2 nerve root caused greater postoperative numbness but less neuralgia and fewer screw malpositions. Similar rates of screw malposition and VAI arose with posterior arch screws and those starting below the arch with C2 nerve preservation, but the latter had greater numbness and pain. CONCLUSION:: A thorough understanding of atlantoaxial anatomy and modern surgical techniques renders the insertion of C1LMS safe and accurate. The incidence of clinically significant malpositioned screws or VAI is less than 0.5%. Sacrifice of the C2 nerve root did result in fewer malpositioned screws. Numbness occurred in 11% of patients, an outcome that may be unacceptable to certain patient populations, but neuropathic pain was nearly absent with nerve sectioning. C2 nerve preservation and retraction for C1 screw placement may have higher incidence of neuropathic pain. Posterior arch screws are a viable option for patients with arches that are of adequate height.

STUDY DESIGN:: Literature review and meta-analysis. OBJECTIVES:: To compare the incidence of screw malposition and vertebral artery injury (VAI) with transarticular screws (TAS) and C2 pedicle screws (C2PS) using meta-analysis techniques. SUMMARY OF BACKGROUND DATA:: Posterior instrumentation for atlanto-axial fusions can be challenging and risky. Some centers report a higher incidence of VAI with the implantation of TAS compared to C2PS, while other data do not support this. METHODS:: Online databases were searched for English-language articles between 1994 and April of 2011 describing the clinical and radiographic outcomes following insertion of C2PS or TAS. Forty-one studies reporting on 3627 TAS and 33 studies describing 2979 C2PS met inclusion criteria for VAI or clinically significant misplacements (VAI, neurological deficits or misplacements requiring surgical revision) and 36 studies reporting on 3280 TAS and 28 studies describing 2532 C2PS met inclusion criteria for radiographic misplacement outcomes. RESULTS:: All studies comprised Class III evidence. VAI occurred in 26 of 3627 (0.72%) implanted TAS and in 10 of 2979 (0.34%) implanted C2PS (P=0.01). Clinically significant misplacements occurred in 67 TAS (1.84%) and in 10 C2PS (0.34%; P<0.0001). The point estimate of VAI for TAS was 1.68% (CI: 1.23-2.29%) and was higher than C2PS (1.09%; CI: 0.73-1.63%; P=0.01). The point estimate of clinically significant screw malposition for TAS was 2.33% (CI: 1.61-3.37%) and was higher than that of C2PS (1.15%; CI: 0.77-1.70%; P<0.001). CONCLUSIONS:: With training, experience and anatomical knowledge, both TAS and C2PS can be inserted accurately and safely. However, improper insertion and VAI can have catastrophic consequences. Our review identified a higher risk of VAI, neurological injury and clinically significant malpositions with TAS compared to C2PS. These data provide preliminary support for the supposition that C2PS have a lower risk of morbidity.