Clinical and radiographic predictive factors for the favorable outcome of lumbar epidural steroid injection in lumbosacral radiculopathy: a prospective analytical study from Thailand

Study Design: A prospective analytic study. Purpose: To investigate the clinical factors and magnetic resonance imaging (MRI) findings that can predict a favorable outcome following transforaminal epidural steroid injection (TFESI) in patients with lumbosacral radiculopathy. Overview of Literature: The efficacy of lumbar epidural steroid injection varies, and no clinical parameters have been established to predict a favorable response to TFESI reliably. Methods: In total, 120 patients diagnosed with lumbosacral radiculopathy underwent TFESI. At each index spinal level, 5.0 mg of a dexamethasone mixture in 2.0% lidocaine and 0.5% bupivacaine was injected. At the 2-week follow-up, a favorable response to TFESI was defined as pain reduction upon movement of >50.0%. Pain manifestation and MRI findings were evaluated. Results: A favorable response was observed in 60.8% of the patients 2 weeks post-TFESI. In the multivariate analysis, patients with mild central canal stenosis had 4.8 times higher odds of a favorable response to TFESI than those with severe central canal stenosis (adjusted odds ratio, 4.8; 95% confidence interval [CI], 1.2-18.8; p=0.023). Favorable responders experienced a notable 29-week period of pain reduction (95% CI, 10.3-47.8), along with a significantly lower incidence of surgery at 12 months (13.7%) (p<0.01). The mean pain score differences of 3.5 out of 10 observed 2 weeks and 1 month post-TFESI represented the optimal sensitivity and specificity in forecasting favorable responder status. Conclusions: A pain reduction of 3.5 out of 10 within 1 month is considered a clinical benchmark for predicting long-term positive outcomes after TFESI. The presence of severe central canal stenosis is significantly associated with an unfavorable response to TFESI.