ABSTRACT
PURPOSE: To analyze survival rates of patients after mono-segmental lumbar or lumbosacral fusion and to evaluate factors affecting the revision operation due to adjacent segmental degeneration. MATERIALS AND METHODS: This study enrolled 1,206 patients who had mono-segmental lumbar or lumbosacral fusion between March 1997 and December 2006 at the Seoul Spine Institute. The survival rates for the revision operation due to adjacent segmental degeneration were analyzed retrospectively. The age at index operation, sex, etiologic diagnosis, fusion method, fusion level, substance of bone graft, operator, body mass index (BMI), and smoking were considered as risk factors for the revision operation. RESULTS: There were 27 patients with a revision operation for adjacent segmental degeneration (2.24%). The average follow-up period was 39.0 months (6 months to 12 years 6 months) and the average age at operation was 47.0 years (13 to 85 years). The survival rate at 5 years was 97.3%, and at 10 years it was 89.4%. Patients less than 50 years old had a significantly lower revision operation rate than those aged 50 or more (p=0.002). When fusion between the 4th lumbar and the 5th lumbar spinal vertebrae was done, the revision operation rate was significantly higher than for other levels (p=0.003). Obese patients with BMI> or =25 had a significantly higher revision rate than did patients with BMI0.05). In multivariate analysis, age alone was a significant risk factor (p=0.048, Hazard ratio=2.50). CONCLUSION: The most important factor for survival without revision surgery for adjacent segmental degeneration following instrumented mono-segment lumbar or lumbosacral fusion is the age at index operation. Patients 50 year-old or older should be informed of the possibility of adjacent segmental disease after instrumented mono-segment lumbar or lumbosacral fusion.