Factors influencing the long-term outcomes of instrumentation surgery for degenerative lumbar spondylolisthesis: a post-hoc analysis of a prospective randomized study

BACKGROUND CONTEXT Lumbar spinal canal stenosis caused by degenerative lumbar spondylolisthesis is one of the most common indications for spinal surgery. However, the factors that influence its long-term (>10 years) outcomes remain unknown. DESIGN This is a post-hoc analysis of a prospective randomized study. PURPOSE This study aimed to determine factors that influence the long-term outcomes of instrumentation surgery for lumbar spinal canal stenosis due to degenerative lumbar spondylolisthesis. PATIENT SAMPLE Patients aged ≤75 years with single L4/5 level lumbar canal stenosis caused by degenerative lumbar spondylolisthesis prospectively underwent instrumentation surgery at two hospitals between May 1, 2003, and April 30, 2012; the final follow-up examination was on May 20, 2021. OUTCOME MEASURES The following data were collected: modified Japanese Orthopedic Association (JOA) score, JOA score recovery rate, visual analog scale (VAS) score for lower back and leg pain, and scores from eight short-form 36 (SF-36) subscales preoperatively and at the final follow-up examination. METHODS Spearman's correlation analysis and univariate and multivariate regression analyses were used to examine preoperative factors that affect the JOA score recovery rate in patients who underwent instrumentation surgery for lumbar spinal canal stenosis at the L4/5 level due to degenerative lumbar spondylolisthesis. RESULTS A total of 42 patients who underwent instrumentation surgery for degenerative lumbar spondylolisthesis and had a long-term follow-up period were included. Of these, 25 and 17 underwent posterolateral fusion and Graf stabilization, respectively. The mean postoperative follow-up duration was 12.5 years. Spearman's correlation analysis revealed that the long-term recovery rate was correlated with the preoperative VAS score for low back pain. In the univariate regression analysis, sex, preoperative VAS score for low back pain, and the SF-36 general health score were significantly associated with the long-term recovery rate. Meanwhile, the multiple stepwise regression analysis identified the preoperative VAS score for low back pain as an independent predictor of the long-term recovery rate. CONCLUSIONS This study identified the preoperative VAS score for low back pain as an independent predictor of the long-term recovery rate following instrumentation surgery for degenerative lumbar spondylolisthesis. Therefore, when performing posterolateral fusion or Graf stabilization for degenerative lumbar spondylolisthesis, attention should be paid to the intensity of preoperative low back pain and considerations should be given to whether these procedures can improve the patient's symptoms in the long term.