Functional Outcome after Decompression and Instrumented Arthrodesis in Degenerative Lumbar Spinal Stenosis: Factors Influencing Unsuccessful Outcome Change

Objective: To determine functional outcome after decompressive laminectomy and instrumented arthrodesis in patients with degenerative lumbar spinal stenosis and identify predictors of failed clinical outcome in these patients. Material and Method: A retrospective cohort data were collected from January 1999 to February 2004. Degenerative lumbar spinal stenosis patients who had decompressive laminectomy and instrumented fusion with pedicular screw system and completed at least 2 years follow-up were enrolled in the present study. Outcomes included Oswestry Disability Index (ODI), Roland Morris score and patient satisfaction. Factors evaluated as outcome variables were age, gender, onset, patient income, associated diseases, smoking, diagnosis of spondylolisthesis or scoliosis, number of levels of instrumentation and presence of S1 fusion. Univariate analysis for factors influencing failed clinical outcome used Chi-square and Fisher exact test and multivariate analysis used the logistic regression. Results: One-hundred and fifty-eight patients were included in the present study. Mean follow-up was 2.64 years (range, 2-5 years). The mean age of the patients at the time of surgery was 60.3 years (range, 34-87 years) and 129 cases (81.7%) were female. According to the US FDA, the criteria of significant successful clinical outcome change is reduction of ODI at least 15%, the proportion of patients reporting significant successful clinical outcome change was 63.9%. Multivariate analysis identified age > 65 years, onset > 24 months and number of levels of instrumentation > 4 as the factors of failed clinical outcome change (p < 0.05). Conclusion: Decompression and instrumented arthrodesis in degenerative lumbar spinal stenosis gained satisfactory functional outcome. Older age, prolonged onset and long level of instrumentation were the factors of failed clinical outcome change.