Which lumbar spinal stenosis patients will improve with nonsurgical treatment? A secondary analysis of a randomized controlled trial.

BACKGROUND: Lumbar spinal stenosis (LSS) can be disabling and is a leading reason for spinal surgery in older adults. While nonsurgical treatments are recommended as first-line treatment, it remains unclear which patients will benefit most. PURPOSE: To identify patient characteristics associated with larger improvements or larger treatment effects among adults receiving nonsurgical LSS interventions. DESIGN: Secondary analysis of a randomized controlled trial. SETTING: Outpatient research clinics. SUBJECTS: 216 older adults with symptomatic LSS. METHODS: Participants, recruited from November 2013 to June 2016, were randomized to receive: (1) manual therapy with an individualized exercise program (MTE); (2) a group exercise (GE) program; or (3) medical care (MC). We evaluated the association of baseline characteristics with 2-month change in primary outcomes: symptoms and function on the Swiss Spinal Stenosis questionnaire (SSSQ); and walking capacity in meters (m) on the self-paced walking test (SPWT). Baseline characteristics included sociodemographic and clinical variables. To explore heterogeneity of treatment effects, we evaluated unadjusted stratified estimates when comparing MTE to GE/MC. Additionally, we included an interaction term in models to test for statistical interaction. RESULTS: At baseline, participants (mean age = 72, 54% female, 23% non-white) had moderate LSS-related symptoms/impairment (mean SSSQ score = 31.3) and limited walking capacity on SPWT (mean = 451 m). The overall improvement on SSSQ was 2.5 points with larger improvements observed among younger, non-white, non-smoking participants, and those with worse baseline LSS or back-related symptoms/impairment. Overall improvement on the SPWT was 205 m with larger improvements observed among younger participants, those with higher baseline physical activity levels and participants without knee osteoarthritis. For SSSQ, the treatment effect was larger among adults aged < 70 versus older adults (MTE vs. GE/MC; mean difference [MD] = - 4.06, 95% CI = - 6.29 to - 1.83 vs. MD = - 0.47. 95% CI = - 2.63 to 1.69, respectively; p-for-interaction = 0.02). For walking capacity, the treatment effect was larger among adults with hip osteoarthritis compared to those without (MTE vs. GE/MC; MD = 500 m, 95% CI = 71 to 929, vs MD = 13 m, 95% CI = - 120 to 147, respectively; p-for-interaction = 0.007). CONCLUSIONS: In a sample receiving nonsurgical treatments for LSS, we identified patient-level characteristics associated with larger improvements and/or treatment effects. If confirmed in larger randomized controlled trials, these findings may guide clinical decision-making to enhance clinical outcomes. GOV IDENTIFIER: NCT01943435.