Instability of the cervical spine after anterior interbody fusion. A study on its incidence and clinical significance in 21 patients.

Twenty-one patients suffering from cervical spondylosis and peripheral symptoms underwent uncomplicated anterior interbody fusion of the cervical spine and were re-examined clinically and radiologically at 27 +/- 15 months (mean +/- SD) after the operation. Translatory displacement of the segment adjacent to the fusion level was noted in 14 patients. Its incidence could not be related to the age and sex of the patient, to extent of the fusion, or to postoperative time. Anterior slippage did not correlate with persistent or recurring pain.