Background context: Epidural corticosteroid injections are commonly used to treat back and leg pain associated with lumbar spinal stenosis. However, little is known about which patient characteristics may predict favorable responses.
Purpose: The aim was to identify patient characteristics associated with benefits from epidural injections of corticosteroid with lidocaine versus epidural injections of lidocaine only for lumbar spinal stenosis symptoms.
Study design/setting: This was a secondary analysis of Lumbar Epidural steroid injections for Spinal Stenosis randomized controlled trial data from 16 US clinical sites.
Patient sample: Patients aged older than or equal to 50 years with moderate-to-severe leg pain and lumbar central spinal stenosis randomized to epidural injections of corticosteroids with lidocaine (n=200) or lidocaine only (n=200) were included.
Outcome measures: Primary outcomes were the Roland-Morris Disability Questionnaire (RMDQ) and 0 to 10 leg pain intensity ratings. Secondary outcomes included the Brief Pain Inventory Interference Scale and the Swiss Spinal Stenosis Questionnaire.
Methods: At baseline, clinicians rated severity of patient spinal stenosis, and patients completed predictor and outcome measures. Patients completed outcome measures again 3 and 6 (primary end point) weeks after randomization/initial injection. Analysis of covariance was used with treatment by covariate interactions to identify baseline predictors of greater benefit from corticosteroid+lidocaine versus lidocaine alone. We also identified nonspecific (independent of treatment) predictors of outcomes.
Results: Among 21 candidate predictors and six outcomes, only one baseline variable predicted greater benefit from corticosteroid+lidocaine versus lidocaine only at 3 or 6 weeks. Compared with patients who rated their health-related quality of life as high on the EQ-5D Index, patients who rated it as poor had greater improvement with corticosteroid than with lidocaine only in leg pain at 6 (but not 3) weeks (interaction coefficient=2.94; 95% confidence interval [CI]=0.11-5.76; p=.04) and in RMDQ disability scores at 3 (but not 6) weeks (interaction coefficient=4.77, 95% CI= -0.04 to 9.59; p = .05). Several baseline patient characteristics predicted outcomes regardless of treatment assignment.
Conclusions: Among 21 baseline patient characteristics examined, none, including clinician-rated spinal stenosis severity, were consistent predictors of benefit from epidural injections of lidocaine+corticosteroid versus lidocaine only.
Keywords: Back pain; Corticosteroid; Epidural steroid injections; Leg pain; Lumbar spinal stenosis; Predictors; Treatment effect modifiers.
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