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John K. Stokes, Alan T. Villavicencio, Paul C. Liu, Robert S. Bray and J. Patrick Johnson

Object

Surgical treatment of atlantoaxial instability has evolved to include various posterior wiring techniques including Brooks, Gallie, and Sonntag fusions in which success rates range from 60 to 100%. The Magerl–Seemans technique in which C1–2 transarticular screws are placed results in fusion rates between 87 and 100%. This procedure is technically demanding and requires precise knowledge of the course of the vertebral arteries (VAs). The authors introduce a new C1–2 fixation procedure in which C-1 lateral mass and C-2 pedicle screws are placed that may have advantages over C1–2 transarticular screw constructs.

Methods

A standard posterior C1–2 exposure is obtained. Polyaxial C-2 pedicle screws and C-1 lateral mass screws are placed bilaterally. Rods are connected to the screws and secured using locking nuts. A cross-link is then placed. Fusion can be performed at the atlantoaxial joint by elevating the C-2 nerve root.

The technique for this procedure has been used in four cases of atlantoaxial instability at the author's institution. There have been no C-2 nerve root– or VA-related injuries. No cases of construct failure have been observed in the short-term follow up period.

Conclusions

Atlantoaxial lateral mass and axial pedicle screw fixation offers an alternative means of achieving atlantoaxial fusion. The technique is less demanding than that required for transarticular screw placement and may avoid the potential complication of VA injury. The cross-linked construct is theoretically stable in flexion, extension, and rotation. Laminectomy or fracture of the posterior elements does not preclude use of this fixation procedure.

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Devender Singh, Eeric Truumees, Dana Hawthorne, John K. Stokes and Matthew J. Geck

Object

The goals of this study were to determine the incidence of occult cervical stenosis in patients over 50 years old with thoracolumbar deformity and to assess the risk of progressive cervical myelopathy after complex thoracolumbar reconstruction in asymptomatic or mildly symptomatic patients with cervical stenosis.

Methods

Charts and cervical imaging for patients who were over 50 years old when they had undergone thoracolumbar deformity surgery between 2005 and 2008 were reviewed. Patients with primary neurological disorders were excluded from the study.

Results

Seventy-three patients (56 women and 17 men) met the study inclusion criteria. The minimum follow-up time was 2 years. Fifty-eight percent of patients (42 of 73) had cervical stenosis on advanced imaging. Thirty-three patients had mild or moderate stenosis; only 3 of these patients had clinical myelopathy. Nine patients (12%) had critical cervical stenosis, as determined from imaging; among these patients, 3 had moderate or severe myelopathy. Patients with noncritical stenosis and no or mild myelopathy underwent thoracolumbar reconstruction without any postoperative progression of myelopathy. Patients with critical stenosis and/or moderate or severe myelopathy were offered cervical decompression prior to thoracolumbar reconstruction; those who accepted this offer did not have progression of myelopathy. One patient underwent thoracolumbar reconstruction first despite critical cervical stenosis. At 20 months, her cervical myelopathy had progressed, and she ultimately required cervical decompression.

Conclusions

Cervical stenosis, even critical stenosis in some cases, was seen in more than one-half of the patients. Most presented without obvious cervical complaints. In those with mild to moderate stenosis and no or mild myelopathy, lengthy thoracolumbar reconstruction procedures were not associated with progression of the myelopathy. The authors recommend that all adults with thoracolumbar deformity undergo a detailed upper- and lower-extremity neurological examination prior to major thoracolumbar reconstruction.

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George A. Alsina, J. Patrick Johnson, Duncan Q. McBride, Patrick R. L. Rhoten, C. Mark Mehringer and John K. Stokes

Worldwide, cysticercosis is the most common parasitic infection of the central nervous system. In endemic regions, the incidence of neurocysticercosis (NCC) approaches 4% of the general population. The disease is predominantly intracranial, the authors of most series generally report the incidence of spinal NCC as only 1.5 to 3% of all cases. Although spinal NCC is relatively rare, it represents a distinct clinical entity that can have devastating consequences for the patient. Because of the limited size of the spinal canal, the mass effect of these lesions is poorly tolerated. Most spinal NCC occurs in the subarachnoid space where mass effect can cause spinal cord compression, although obstruction of cerebrospinal fluid pathways due to scarring of the subarachnoid space can also cause symptoms.

The authors treated six patients with spinal NCC. In five cases the lesions were located in the subarachnoid space, and in one the lesion was intramedullary. All patients with subarachnoid spinal NCC required excision of the symptomatic lesions; in two cases initial medical therapy had failed. The patient with intramedullary spinal NCC experienced mild symptoms and underwent steroid therapy. All patients experienced variably improved outcomes and were eventually ambulatory.

Medical therapy should be carefully considered in selected patients in whom symptoms are stable and nonprogressive. Surgical intervention is required when severe or progressive deficits occur to prevent permanent injury. In some patients recovery may be limited as a result of inflammatory injury to the spinal cord or arachnoidal adhesions.

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Reginald J. Davis, Kee D. Kim, Michael S. Hisey, Gregory A. Hoffman, Hyun W. Bae, Steven E. Gaede, Ralph F. Rashbaum, Pierce Dalton Nunley, Daniel L. Peterson and John K. Stokes

Object

Cervical total disc replacement (TDR) is intended to treat neurological symptoms and neck pain associated with degeneration of intervertebral discs in the cervical spine. Anterior cervical discectomy and fusion (ACDF) has been the standard treatment for these indications since the procedure was first developed in the 1950s. While TDR has been shown to be a safe and effective alternative to ACDF for treatment of patients with degenerative disc disease (DDD) at a single level of the cervical spine, few studies have focused on the safety and efficacy of TDR for treatment of 2 levels of the cervical spine. The primary objective of this study was to rigorously compare the Mobi-C cervical artificial disc to ACDF for treatment of cervical DDD at 2 contiguous levels of the cervical spine.

Methods

This study was a prospective, randomized, US FDA investigational device exemption pivotal trial of the Mobi-C cervical artificial disc conducted at 24 centers in the US. The primary clinical outcome was a composite measure of study success at 24 months. The comparative control treatment was ACDF using allograft bone and an anterior plate. A total of 330 patients were enrolled, randomized, and received study surgery. All patients were diagnosed with intractable symptomatic cervical DDD at 2 contiguous levels of the cervical spine between C-3 and C-7. Patients were randomized in a 2:1 ratio (TDR patients to ACDF patients).

Results

A total of 225 patients received the Mobi-C TDR device and 105 patients received ACDF. At 24 months only 3.0% of patients were lost to follow-up. On average, patients in both groups showed significant improvements in Neck Disability Index (NDI) score, visual analog scale (VAS) neck pain score, and VAS arm pain score from preoperative baseline to each time point. However, the TDR patients experienced significantly greater improvement than ACDF patients in NDI score at all time points and significantly greater improvement in VAS neck pain score at 6 weeks, and at 3, 6, and 12 months postoperatively. On average, patients in the TDR group also maintained preoperative segmental range of motion at both treated segments immediately postoperatively and throughout the study period of 24 months. The reoperation rate was significantly higher in the ACDF group at 11.4% compared with 3.1% for the TDR group. Furthermore, at 24 months TDR demonstrated statistical superiority over ACDF based on overall study success rates.

Conclusions

The results of this study represent the first available Level I clinical evidence in support of cervical arthroplasty at 2 contiguous levels of the cervical spine using the Mobi-C cervical artificial disc. These results continue to support the use of cervical arthroplasty in general, but specifically demonstrate the advantages of 2-level arthroplasty over 2-level ACDF. Clinical trial registration no.: NCT00389597 (ClinicalTrials.gov).