Long-term follow-up study of posterior lumbar interbody fusion.

To see whether degenerative changes of the adjacent disks are accelerated by fixation of a lumbar segment, 48 patients who had undergone posterior lumbar interbody fusion (PLIF) more than 5 years previously were investigated radiographically and clinically. Narrowing of disk spaces was observed in 31% of the subjects, but it usually occurred at levels proximal to the fusion. The incidence of adjacent disk narrowing was not significantly higher after PLIF, compared with reports on degenerative changes of lumbar disks with aging. Some subjects showed narrowing of disks that were not adjacent to the fused level, suggesting that individual predisposition played a role in disk narrowing. Instability was not seen in any of the subjects. New development or elongation of the traction spurs at adjacent segments occurred at the disks proximal to the fusion. The clinical results were generally satisfactory, despite progression of degenerative changes on radiographs.