Faculty Bibliography

OBJECTIVE: Iliac crest autograft remains the gold standard for spinal fusion operations. Given risk of donor site morbidity, many centers utilize allograft. We reviewed published series of C1-2 posterolateral instrumented fusions with allograft and autograft. METHODS: Online databases were searched for English-language articles reporting quantifiable outcome data published between 1994 and 2011 of posterior atlantoaxial instrumented arthrodesis with C1 and C2 screws. Thirteen studies describing 652 patients having autograft and seven studies describing 60 patients having allograft serve as the basis of this report. RESULTS: All studies were retrospective case series (Class III evidence). There were no differences in complications or mortality between the groups. There were trends toward shorter operative times and less blood loss using allograft. A higher proportion of patients in the allograft group underwent sacrifice of the C2 nerve root and decortication and packing of the C1-2 joints (P<0.0001). There was no significant difference in the proportion of surviving patients who achieved solid fusion in the autograft (642 of 644 [99.7%]) and allograft patients (59 of 59 [100%]; P = 1.0). CONCLUSIONS: This review is limited by the retrospective data and inconsistent methodology of fusion determination used in most studies. Modern instrumentation and proper surgical techniques result in high rates of successful C1-2 arthrodesis. The use of allograft is a treatment option (Class III evidence) during posterior C1-2 instrumentation and fusion operations. Randomized, controlled trials using standardized radiographic assessments are needed across spinal arthrodesis studies to better determine the prevalence of radiographic fusion and establish technique superiority.

OBJECTIVE: To analyze qualitatively C2 nerve dysfunction after its transection in C1-2 posterolateral instrumented fusions. METHODS: From 2002-2010, 20 consecutive patients underwent posterolateral instrumented fusions using C1 lateral mass and C2 pars or pedicle screws, mainly for type 2 dens fractures. Screws were placed under lateral fluoroscopic guidance using standard techniques. Bilateral C2 nerve roots were coagulated and transected in all patients. Mean follow-up was 30.7 months and consisted of clinical and radiographic examinations, telephone interviews, and mailed visual analogue scale (VAS) questionnaires assessing C2 nerve dysfunction. RESULTS: One patient was lost to follow-up after the initial postoperative visit. Fusion was evident in all patients with 12 months of follow-up and two of three patients with <12 months of follow-up. There were no instances of unintended neurologic deficits, vascular injury, cerebrospinal fluid (CSF) leak, or hardware malfunction or malposition. By the 2-week or 6-week office visit, 4 of 20 patients complained of sensory disturbance, and 2 had paresthesias in the C2 distribution. After longer follow-up, one additional patient developed mild sensory symptoms. Quality of life was adversely affected in only one patient. No patient developed neuropathic pain at any time after C2 sectioning. CONCLUSIONS: This study is the first series to describe C2 nerve function after posterior atlantoaxial instrumented fusion in adults of all ages. Sacrifice of the C2 nerve root increases fusion surface, allows for better preparation and decortication of the atlantoaxial joint, improves visualization for screw placement, and decreases blood loss and operative time without major clinical consequences.

INTRODUCTION:: Iatrogenic arterial injury is an uncommon but recognized complication of posterior spinal surgery. The spectrum of injuries includes vessel perforation leading to hemorrhage, delayed pseudoaneurysm formation, and threatened perforation by screw impingement on arterial vessels. Repair of these injuries traditionally involved open direct vessel repair or graft placement, which can be associated with significant morbidity. METHODS:: We identified five cases of iatrogenic arterial injury during or after posterior spinal surgery between July 2004 and August 2009 and describe the endovascular treatment of these five patients. RESULTS:: In two patients, intraoperative arterial bleeding was encountered during posterior spinal surgery. The posterior wounds were packed, temporarily closed, and the patients were placed supine. Angiography in both patients demonstrated arterial injury necessitating repair. Covered stent grafts were deployed through femoral cutdowns to exclude the areas of injury. In three additional patients, postoperative computed tomography imaging demonstrated pedicle screws abutting or penetrating the thoracic or abdominal aorta. In all three patients, angiography or intravascular ultrasound (IVUS), or both, confirmed indention or perforation of the aorta by the screw. Aortic stent graft cuffs were deployed through femoral cutdowns to cover the area of aortic contact before hardware removal. All five patients did well and were discharged home in good condition. CONCLUSIONS:: Endovascular repair of arterial injuries occurring during posterior spine procedures is feasible and can offer a safe and less invasive alternative to open repair

BACKGROUND CONTEXT: Large cell neuroendocrine carcinoma of the lung is an aggressive tumor with unique histopathological features. It is not known to metastasize to the spine. PURPOSE: To report a metastatic case of this rare tumor to the cauda equina. STUDY DESIGN: Case report. METHODS: Retrospective case review and review of the literature. RESULTS: The authors report a rare case of a large cell neuroendocrine lung metastasis to the lumbar spine, causing right foot drop. Magnetic resonance imaging revealed a heterogeneously enhancing intradural extramedullary mass at L2/L3 level compressing the surrounding nerve roots. During surgery, the identified nerve roots were encased by the tumor, and the dissection was tedious. Postoperatively, the patient reported significantly improved back pain and he had severe foot weakness. The functional outcome was poor because the patient lost entirely his foot function; however, his back pain improved significantly after surgery. CONCLUSIONS: This is the first published study in which the authors described a metastasis of a rather uncommon lung cancer to the cauda equina. When a lesion of the cauda equina presents with a rapid progressive neurological deficit, leptomeningeal metastasis should be in the differential diagnosis.

Metameric lesions of the spine are rare. The authors present a case of patient with a complex metameric vascular lesion of the thoracic spine and describe a management strategy for this entity

BACKGROUND: C1-C2 fusion has significantly advanced from predominantly wiring/cable modalities to more biomechanically stable screw-rod techniques. Minimally invasive surgical techniques represents the most recent modification of atlantoaxial fixation. The indications, rationale, and surgical technique of this novel procedure are described. METHODS: Six patients requiring C1-C2 fusion (5 type II odontoid fractures and 1 os odontoideum) underwent minimally invasive C1-C2 fusion over a 2-year period. The cohort consisted of 5 men and 1 woman with a mean age of 51 years (age range, 39-64 y). All 6 patients underwent bilateral segmental atlantoaxial fixation using an expandable tubular retractor. RESULTS: The mean follow-up time was 32 months (age range, 24-46 mo) There were no intraoperative complications, and the mean estimated blood loss was 100 mL. Solid fusion was achieved in all 6 patients, without pathological motion on dynamic studies. Postoperative computed tomographic images showed no hardware malposition in the scanned patients (4 of the 6 patients). CONCLUSIONS: Placement of C1 and C2 instrumentation using minimally invasive techniques is technically feasible. Because the instrumentation and the means of obtaining arthrodesis do not differ substantively from the standard approach, we would not anticipate long-term results to be different from those of an open procedure, apart from the approach-related morbidity.

Anteriorly located Type IV thoracic arteriovenous malformations (AVMs) are difficult to treat surgically. Although high-flow fistula subtypes are amenable to treatment using endovascular techniques, low-flow fistulas should be treated surgically. There are few reports discussing the diagnosis, behavior, and treatment of these spinal fistulas due to their low incidence. Posterior surgical approaches to Type IV spinal AVMs reported in the literature have been associated with high morbidity rates or aborted procedures. The authors report the successful management of a T-12 Type IV spinal AVM with an emphasis on approach, interoperative angiography, and the use of modern instrumentation. To the authors' knowledge, this is also the first reported case of multiple arterial-side aneurysms in a Type IV AVM of the anterior spinal artery

OBJECTIVE AND IMPORTANCE: Posterior C1-C2 fusion with polyaxial screw and rod fixation has become an accepted means of atlanto-axial stabilization. We describe a novel technique for minimally invasive placement of C1 lateral mass screws and C2 pedicle screws for polyaxial screw-rod stabilization. CLINICAL PRESENTATION: The patient presented with a history of chronic neck pain, as well as a 6-month history of weakness and paresthesias involving her left hand. An Os Odontoideum was present on computed tomographic imaging of the cervical spine. Significant instability was noted on flexion-extension imaging, and magnetic resonance imaging demonstrated mild T2 signal change within the spinal cord. TECHNIQUE: Under fluoroscopic guidance, serial dilators were passed through a 2.5 cm paramedian skin incision to allow placement of an expandable tubular retractor. The exposure was centered on the C2 lateral mass. After expansion of the retractor and further subperiosteal dissection, the C1 and C2 lateral masses were visible permitting placement of a polyaxial screw rod construct. This procedure was carried out bilaterally. CONCLUSION: Placement of C1 lateral mass and C2 pedicle screws using minimally invasive techniques is technically feasible

OBJECTIVE: Disc herniations at the C7-T1 level are unusual (4% of all herniated cervical discs) and are often incorrectly diagnosed because of unusual neurological findings and suboptimal imaging studies. Furthermore, the anterior approach may be problematic because the manubrium and slope of the vertebral bodies away from the surgeon obscures the end plates. The recurrent laryngeal nerve and the thoracic duct may be injured by respective right- or left-sided approaches. A posterior approach to this level has, therefore, been advocated, but results of C7-T1 herniations treated anteriorly have not been specifically addressed in the literature. We, therefore, reviewed our experience in the operative management of patients undergoing single level anterior cervical discectomy and fusion at the C7-T1 interspace for the 10 years ending June 2004 with regard to clinical presentation, imaging, problems of operative exposure, and neurological outcome. METHODS: Of 268 patients with single level anterior cervical discectomy and fusions (ACDFs), 10 (3.7%) had C7-T1 disc herniations. We retrospectively reviewed the medical records, operative reports, and imaging studies of these 10 patients. RESULTS: All patients presented with C8 motor deficit without myelopathy. The operation was carried out through an anterior approach with a skin incision 3 cm above the clavicle. Visualization of the C7-T1 disc space was achieved in all without difficulty. Eight of 10 patients are neurologically intact. CONCLUSION: The C7-T1 disc herniates laterally because of the absence of Luschka joints at this level. Central herniation with myelopathy is rare. An anterior approach was easily accomplished in all patients. Recovery of motor function was related to duration and severity of preoperative deficit