Risk-factor analysis of adjacent-segment pathology requiring surgery following anterior, posterior, fusion, and nonfusion cervical spine operations: survivorship analysis of 1358 patients.

BACKGROUND Adjacent-segment pathology is an important issue involving the cervical spine, but there have been few comprehensive studies of this problem. The purpose of the current study was to determine the risk factors for adjacent-segment pathology and to compare the survivorship of adjacent segments in patients who underwent cervical spine operations including arthrodesis and motion-sparing procedures. METHODS This was a retrospective analysis of a consecutive series of 1358 patients with radiculopathy, myelopathy, or myeloradiculopathy who underwent cervical spine surgery performed by a single surgeon. We calculated the annual incidence of adjacent-segment pathology requiring surgery and, with use of Kaplan-Meier analysis, determined survivorship. Cox regression analysis was used to identify risk factors. RESULTS The index surgical procedures included cervical arthrodesis (1095 patients; 1038 anterior, twenty-nine posterior, and twenty-eight combined anterior and posterior), posterior decompression (214 patients; 145 laminoplasty and sixty-nine foraminotomy), arthroplasty (thirty-two patients), and a combination of arthroplasty and anterior arthrodesis (seventeen patients). Secondary surgery on adjacent segments occurred at a relatively constant rate of 2.3% per year (95% confidence interval, 1.9 to 2.9). Kaplan-Meier analysis predicted that 21.9% of patients would need secondary surgery on adjacent segments by ten years postoperatively. Factors increasing the risk were smoking, female sex, and type of procedure. The posterior arthrodesis group (posterior-only or combined anterior and posterior arthrodesis) had a 7.5-times greater risk of adjacent-segment pathology requiring reoperation than posterior decompression, and a 3.0-times greater risk than the anterior arthrodesis group. However, when we compared the anterior cervical arthrodesis group, the arthroplasty group (arthroplasty or hybrid arthroplasty), and the posterior decompression group to each other, there were no significant differences. Age, neurological diagnosis, diabetes, and number of surgically treated segments were not significant risk factors. CONCLUSIONS Patients treated with posterior or combined anterior and posterior arthrodesis were far more likely to develop clinical adjacent-segment pathology requiring surgery than those treated with posterior decompression or anterior arthrodesis. Smokers and women had a higher chance of clinical adjacent-segment pathology after cervical spine surgery.