[Segment changes in the cervical spine following cervical spondylodeses of unstable injuries].

Radiologic and functional assessments were performed in 60 patients who underwent cervical fusion for traumatic instability. Follow up range was one to eight years (average 3.9 years). 235 motion segments (C2/3 to C7/th1) were analyzed. Follow up radiologic examination included a.p., flexion-extension and oblique cervical spine films. Each motion segment was analyzed for range of mobility according the method of Penning. Total range of spinal motion was recorded, radiologic disc appearance and spondylophyte formation were also classified. The most striking findings included 15 "nose-like" and eleven "bridging" spondylophytes noted anteriorly on the lateral views. Segmental function was diminished an average of 67.8% in "noses" and 46.6% in "bridges". Since the disc height remained radiologically normal, and osteophytes were located exclusively anterior, adjacent to the fusions, these changes were interpreted as secondary to excessive dissection along the anterior longitudinal ligament or the improper placement of the plates. In seven cases rapid development of degenerative change was attributed to previously undetected traumatic insult to a normal motion segment. This resulted in significant loss of function in all cases. In 134 non-adjacent motion segments no spondylophyte formation or disc degeneration secondary to operation or trauma was found. Of 235 motion segments, ten adjacent and five non-adjacent segments in nine patients were found to show increased degenerative changes. In this population the average patient age was 51 years (significantly higher than the group average of 38.7 years). The function of these segments was only 45.2% of normal. With historical controls the incidence of increased degenerative changes of the non-fused segments is at no greater risk for early degenerative phenomena than the population at large. 1. Cervical fusion for traumatic instabilities carries a higher risk for the adjacent motion segments, but lower than the risk in patients with deforming spondylosis. Careful operative technique can offer a distinct decrease in postoperative spondylophyte formation. 2. Non fused motion segments in this study were affected by degenerative disease at a rate approximately equal to the general population. 3. This investigation revealed no hypermobility in any non-fused motion segment. 4. Even radiologically normal segments could reveal a diminished range of motion.