Sagittal alignment as a risk factor for adjacent level degeneration: a case-control study.

This study examined whether sagittal alignment, preexisting adjacent level degeneration, and smoking predispose patients to adjacent segment degeneration following lumbar fusion. Fifty-one patients with adjacent segment degeneration were identified and matched with control patients based on age, sex, level, and date of index surgery. Preexisting adjacent level degeneration and sagittal alignment through the fusion and from L1-S1 were determined before and after initial surgery. Patients with adjacent segment degeneration had significantly less lordosis through the fusion and lumbar spine following their initial surgery. There was no significant difference in the amount of preexisting adjacent level degeneration and smoking between the adjacent segment degeneration and control groups. Fusion of the lumbar spine in abnormal sagittal alignment, with loss of lumbar lordosis, predisposes patients to the development of adjacent segment degeneration. Adjacent segment degeneration does not appear to be just a progression of preexisting degenerative changes at the adjacent level.