The effect of surgical and nonsurgical treatment on longitudinal outcomes of lumbar spinal stenosis over 10 years.

OBJECTIVES: To assess the relative effect of initial surgical and nonsurgical treatment on longitudinal outcomes of patients with lumbar spinal stenosis over a 10-year follow-up period.
DESIGN: A prospective observational cohort study.
SETTING: Enrollment from community-based specialist practices throughout Maine. PARTICIPANTS: One hundred forty-four patients with lumbar spinal stenosis who had at least one follow-up: 77 initially treated surgically and 67 initially treated nonsurgically. INTERVENTION: Initial surgical or nonsurgical treatment. MEASUREMENTS: Clinical data were obtained at baseline and outcomes followed at regular intervals over 10 years with mailed questionnaires including patient-reported symptoms of back pain, leg symptoms, back-specific functional status, and satisfaction. Longitudinal data were analyzed using general linear mixed models. In addition to treatment (initial surgical or nonsurgical care), time period, and the interaction between treatment and time, the models included baseline score, patient age and sex, and a time-varying general health status score. The effects of these covariates in explaining differences between treatment groups were also examined. The effect of subsequent surgical procedures was assessed using different analysis strategies.
RESULTS: The 10-year rate of subsequent surgical procedures was 23% and 38% for patients initially treated surgically and nonsurgically, respectively, and the overall 10-year survival rate was 69%. Patients undergoing initial surgical treatment had worse baseline symptoms and functional status than those initially treated nonsurgically. For all outcomes and at each time point, surgically treated patients reported greater improvement in symptoms and functional status and higher satisfaction scores, indicative of better outcomes, than nonsurgically treated patients. However, the relative magnitude of the benefit diminished over time such that the relative differences for low back pain and satisfaction were no longer significant over long-term follow-up (both P=.08 for treatment effect between 5 and 10 years after controlling for covariates). Regardless of initial treatment received, patients undergoing subsequent surgical procedures reported less improvement in outcomes over time than patients who did not undergo subsequent procedures, but the relative differences between treatment groups were similar in analyses that controlled for outcomes after subsequent procedures.
CONCLUSION: After controlling for covariates, patients initially treated surgically demonstrated better outcomes on all measures than those initially treated nonsurgically. Although outcomes of initial surgical treatment remained superior over time, the relative benefit of surgery diminished in later years, especially for low back pain and satisfaction. Patients undergoing subsequent surgery had worse outcomes regardless of initial treatment received, but excluding them did not change overall treatment group comparisons. The analytical methods described may be helpful in the design and analysis of future studies comparing treatment outcomes for patients with lumbar spinal stenosis.