Biomechanical comparison of anterior, posterior, and circumferential fixation after one-level anterior cervical corpectomy in the human cadaveric spine.

STUDY DESIGN: In vitro biomechanical study of cadaveric cervical spine. OBJECTIVE: To compare the rigidity of the cervical spine after anterior, posterior, and circumferential fixation after 1-level corpectomy, and evaluate the effects of the integrity of the facet capsules and posterior ligaments (PL). SUMMARY OF BACKGROUND DATA: Anterior cervical corpectomy is commonly used for decompression of the spinal canal in the treatment of different pathologic conditions. The effect of the integrity of the facet capsules and PLs on the biomechanical stability provided by anterior, posterior, or circumferential fixation following 1-level corpectomy has not been investigated. METHODS: Nine cadaveric cervical spines were potted rostrally at C2, and caudally at T1-T2, and were tested in 6 directions with pure moment application, in 5 conditions: In the intact spine, after a C5 corpectomy and anterior fixation, after anterior fixation and disruption of the C4-C5 and C5-C6 facet capsules and PL, after circumferential fixation, and after posterior fixation alone without anterior cage. Angular motion of C4 relative to C6 was measured. RESULTS: Despite C5 corpectomy, anterior grafting and plate fixation was more rigid than the intact spine with all loads in flexion, at loads of 0.5 Nm and 1.0 Nm in right axial rotation and right lateral bending, and at all loads in left lateral bending. Posterior ligamentous disruption increased motion in the coronal and axial planes, but not in the sagittal plane. Circumferential instrumentation resulted in a significant reduction in motion of the spine compared with anterior instrumentation in both the coronal and axial planes but not in the sagittal plane. Posterior fixation without anterior cage failed to limit cervical spine motion in the sagittal plane, but was restrictive in axial rotation and lateral bending when compared with circumferential fixation. CONCLUSION: After C5 corpectomy, with intact PLs and facet capsules, anterior instrumentation is sufficient for spinal stabilization as the resultant construct is more rigid than the intact state. In the presence of C5 corpectomy with PL and bilateral facet capsule disruption, anterior plus posterior instrumentation is more rigid than anterior instrumentation alone in the axial and coronal planes and more rigid than posterior instrumentation without anterior cage in the sagittal plane.

Posterolateral approaches to the craniovertebral junction.

OBJECTIVE: The indications and operative technique for a number of posterolateral approaches to the craniovertebral junction (CVJ) are reviewed. METHODS: The literature addressing posterolateral approaches to the CVJ is reviewed, and illustrative cases are presented. RESULTS: The far lateral approach and its variants, including the transcondylar, supracondylar, and paracondylar approaches, are an effective means of addressing intradural anterior and anterolateral CVJ lesions. These approaches provide exposure of the lower third of the clivus, the foramen magnum, and the upper cervical spine; do not cross contaminated regions; and enable a watertight dural closure to be performed. They are associated with minimal morbidity and usually do not significantly decrease the stability of the CVJ. CONCLUSION: All surgeons treating lesions of the CVJ should be familiar with the posterolateral approach and its modifications.

Occipital condyle fractures.

OBJECTIVE: The anatomy, clinical presentation, radiologic evaluation, treatment, and outcome of occipital condyle fractures are reviewed. METHODS: We review and discuss the literature on occipital condyle fractures. RESULTS: Occipital condyle fractures are best diagnosed with computed tomography. The neurologic presentation is variable. The majority of these injuries may be treated nonoperatively, but an occipitocervical fusion is necessary to restore stability across the craniovertebral junction. CONCLUSION: Occipital condyle fractures are a rare but serious injury that requires prompt diagnosis and treatment.