Background: A primary concern after posterior lumbar spine
arthrodesis is the potential for adjacent segment degeneration cephalad or
caudad to the fusion segment. There is controversy regarding the subsequent
degeneration of adjacent segments, and we are aware of no long-term studies
that have analyzed both cephalad and caudad degeneration following posterior
arthrodesis. A retrospective investigation was performed to determine the
rates of degeneration and survival of the motion segments adjacent to the site
of a posterior lumbar fusion.
Methods: Two hundred and fifteen patients who had undergone
posterior lumbar arthrodesis were included in this study. The study group
included 126 female patients and eighty-nine male patients. The average
duration of follow-up was 6.7 years. Radiographs were analyzed with regard to
arthritic degeneration at the adjacent levels both preoperatively and at the
time of the last follow-up visit. Disc spaces were graded on a 4-point
arthritic degeneration scale. Correlation analysis was used to determine the
contribution of independent variables to the rate of degeneration.
Survivorship analysis was performed to describe the degeneration of the
adjacent motion segments.
Results: Fifty-nine (27.4%) of the 215 patients had evidence of
degeneration at the adjacent levels and elected to have an additional
decompression (fifteen patients) or arthrodesis (forty-four patients).
Kaplan-Meier analysis predicted a disease-free survival rate of 83.5% (95%
confidence interval, 77.5% to 89.5%) at five years and of 63.9% (95%
confidence interval, 54.0% to 73.8%) at ten years after the index operation.
Although there was a trend toward progression of the arthritic grade at the
adjacent disc levels, there was no significant correlation, with the numbers
available, between the preoperative arthritic grade and the need for
Conclusions: The rate of symptomatic degeneration at an adjacent
segment warranting either decompression or arthrodesis was predicted to be
16.5% at five years and 36.1% at ten years. There appeared to be no
correlation with the length of fusion or the preoperative arthritic
degeneration of the adjacent segment.
Level of Evidence: Prognostic study, Level IV (case
series). See Instructions to Authors for a complete description of levels of