Does pain score in response to a standardized subcutaneous local anesthetic injection predict epidural steroid injection outcomes in patients with lumbosacral radiculopathy? A prospective correlational study.

OBJECTIVE Epidural steroid injections (ESI) are the most commonly performed pain procedures. Despite numerous studies, controversy continues to surround their effectiveness. The purpose of this study is to determine whether a standard, clinical local anesthetic injection can predict outcomes for ESI. STUDY DESIGN In this multicenter study, 103 patients received two ESI 2 weeks apart. Prior to their first injection, subjects rated the pain intensity of a standardized subcutaneous (SQ) injection of lidocaine prior to the full dose. Numerical rating scale pain scores were correlated with leg and back pain relief, and functional improvement, through 3-month follow-up. OUTCOME MEASURES A composite successful outcome was predetermined to be a ≥2-point decrease in leg pain score, coupled with a positive global perceived effect. RESULTS A small but significant relationship was found between SQ pain score and reduction in leg (r = -0.21, 95% CI -0.38 to -0.04; P = 0.03) and back pain (r = -0.22, 95% CI -0.36 to -0.07; P = 0.03). Subjects with a positive outcome at 1 month had a mean SQ pain score of 2.5 (SD 1.9) vs 4.1 (SD 2.7) in those with a negative outcome (P = 0.04). Subjects with SQ pain scores <4/10 had lower leg and back pain scores than those with pain scores ≥4 at 1-month (mean 3.2, SD 2.6 vs 5.1, SD 2.7 for leg, P < 0.01; mean 3.7, SD 2.6 vs 5.0, SD 3.0 for back, P = 0.02) and 3-month (mean 3.8, SD 2.7 vs 5.2, SD 3.1 for leg, P = 0.01; mean 4.0, SD 2.6 vs 4.9, SD 3.1 for back; P = 0.14) follow-up. CONCLUSIONS The results of this study found a weak positive correlation between SQ pain scores and treatment results. Further research should consider whether pain perception in conjunction with other variables might prove to be a reliable predictor for ESI and other procedural outcomes.