PubMed · 13301662
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S WERNE. 1955. Spontaneous atlas dislocation.. https://doi.org/10.3109/17453675508998922
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STUDY DESIGN: This biomechanical study used flexibility testing on fresh-frozen human cadaveric specimens (occiput to C3) and compared the range of motion and neutral zone for three occipitocervical fixation techniques. OBJECTIVES: To contrast the stabilization provided by a new technique of anterior occipitocervical screw fixation with two other commonly used posterior occipitocervical fixation techniques. SUMMARY OF BACKGROUND DATA: There are no published reports describing this novel technique of anterior occipitocervical screw fixation. METHODS: Six human occipitocervical spine specimens were mounted in a custom-designed, spine-testing machine that applied a pure moment in flexion-extension, lateral bending, and axial rotation. The specimens were tested intact, after an odontoid osteotomy with capsular injury, and after each of three fixation methods: posterior wiring, posterior plate fixation with C1-C2 transarticular screws, and finally with anterior occipitocervical screws. Intervertebral motion was measured with an optoelectronic measurement system, and the range of motion and neutral zone were the kinematic variables measured and used for analysis. RESULTS: In flexion and extension testing, the posterior plate with transarticular screws provided greater stabilization than posterior wiring or anterior occipitocervical screws. In lateral bending and rotation, the anterior screws were similarly effective to the posterior plate, both of which were more effective than posterior wiring. CONCLUSION: The anterior screw fixation technique was as effective as a posterior plate with transarticular screws in stabilizing between the occiput and C2 in axial rotation and lateral bending. In extension and flexion, the anterior screw technique was not as effective as a posterior plate with transarticular screws in providing stability.
Cervical spondylolysis is a rare clinical entity and occurs predominantly at the C-6 level. The authors describe a patient with congenital spondylolysis of the axis that caused myelopathy. The patient was a 57-year-old woman with long-standing gait disturbance. Plain cervical radiography revealed a radiolucent defect across the pedicle of the axis. Magnetic resonance imaging of the cervical spine in the neutral, flexion, and extension neck positions as well as a computerized tomography myelography in the neutral neck position failed to demonstrate any spinal cord compression. When she rotated her neck, however, the spinal cord was caught between the hypertrophic anterior arch of the atlas and posterior part of the slipped pedicle of the axis on the contralateral side. The spinal cord was transformed into a pear shape. Mechanical injury to the spinal cord seemed to explain her neurological presentation. This is, to the authors' knowledge, the 15th case of axial spondylolysis and the sixth case of spinal cord involvement of the cervical spondylolysis. No cases involving myelopathy secondary to such a unique mechanism have been reported previously in the literature.