179. Predictors of clinical outcome following surgery for lumbar spinal stenosis: a study of postoperative pain and disability trajectories

Abstract

BACKGROUND CONTEXT On average, patients experience important reductions in pain and disability following surgery for degenerative lumbar spinal stenosis (LSS). However, variability in the postoperative course of symptoms suggests many patients do not fit the average symptom trajectory. PURPOSE To identify patient subgroups defined by trajectories of pain and disability following surgery for LSS and investigate the construct validity of the subgroups by evaluating meaningful differences in clinical outcomes. Identify predictors of belonging to the poor outcomes subgroup for disability, leg pain and back pain. STUDY DESIGN/SETTING Retrospective analysis of prospectively collected data. PATIENT SAMPLE Patients with LSS were recruited from 13 surgical spine centers participating in the Canadian Spine Outcomes and Research Network registry. OUTCOME MEASURES Leg and back pain numeric rating scales and the modified Oswestry disability index were measured before surgery and at 3, 12, and 24 months following surgery. METHODS Patients were fit into pain and disability trajectory subgroups with group-based trajectory modeling. Differences in the proportion of patients achieving minimum clinically important change in pain and disability (30%) and clinical success (50% reduction in disability or Oswestry score ≤22) were examined. Generalized linear mixed models adjusted for age and sex, were used to identify associations between subgroup membership and preoperative demographic, clinical history, health status and surgical factors. The subgroup with excellent outcomes was used as the reference group; associations were reported with relative risk ratios (RR). RESULTS The group-based trajectory models identified 3 unique pain trajectories each (excellent, fair and poor) for leg pain, back pain and disability. Depending on outcome 29% to 42% of patients were classified as members of an outcome trajectory subgroup that experienced little to no benefit from surgery. The construct validity of the trajectory subgroups was supported by differences in the proportion of patients meeting thresholds for minimum clinically important change and clinical success (p CONCLUSIONS The percentage of patients with poor outcomes highlights the need for better methods of treatment selection for patients with LSS. The predictors of having poor outcomes suggests it is time to look beyond pathology/surgical factors only and include mental health variables as an integral part of the surgical decision-making process in an effort to avoid patients at increased risk for surgical failure. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.