Adjacent Segment Degeneration after Single-Level PLIF: Comparison between Spondylolytic Spondylolisthesis, Degenerative Spondylolisthesis and Spinal Stenosis

STUDY DESIGN: A retrospective study. PURPOSE: To comparatively investigated the rate of the adjacent segment degeneration and the clinical outcomes in patients with spondylolytic spondylolisthesis, spinal stenosis or degenerative spondylolisthesis. OVERVIEW OF LITERATURE: There have been few studies reported on the adjacent segment degeneration following posterior lumbar interbody fusion(PLIF). Many risk factors for the adjacent segment degeneration following PLIF have been proposed. The range of decompression has been presented as one of the risk factors, yet controversial. METHODS: This study enrolled sixty-three patients who had been treated with single-level PLIF and who were followed up for more than two years. The patients were divided into 3 groups based on the preoperative diagnosis. We analyzed the difference between the preoperative and postoperative intervertebral disc heights of the superior adjacent segments. The incidence rates of instability and the clinical outcomes were comparatively analyzed between each group. RESULTS: The average age of the patients was 55.8 years in the spondylolytic spondylolisthesis group, 65.9 years in the degenerative spondylolisthesis group and 60.4 years in the spinal stenosis group. The average follow-up period was 44 months, 43 months and 42 months, respectively. At the last follow-up, compared to the preoperative period, the intervertebral disc height decreased in all three groups. A statistically significant decrease (p < 0.01) was observed only in the spondylolytic spondylolisthesis group and no significant difference was observed between each group (p = 0.41). The incidence rate of instability and the clinical outcome were not significantly different between each group. CONCLUSIONS: Spondylolytic spondylolisthesis with total laminectomy and single-level PLIF showed no significant difference in the superior adjacent segment degeneration and instability, and the clinical outcome as compared to that of partial laminectomy with single-level PLIF for treating degenerative spondylolisthesis or spinal stenosis.