Extended Follow-up of Local Steroid Injection for Carpal Tunnel Syndrome: A Randomized Clinical Trial

Importance: Local steroid injection is commonly used in treating patients with idiopathic carpal tunnel syndrome, but evidence regarding long-term efficacy is lacking. Objective: To assess the long-term treatment effects of local steroid injection for carpal tunnel syndrome. Design, Setting, and Participants: This exploratory 5-year extended follow-up of a double-blind, placebo-controlled randomized clinical trial was conducted from November 2008 to March 2012 at a university hospital orthopedic department. Participants included patients aged 22 to 69 years with primary idiopathic carpal tunnel syndrome and no prior treatment with local steroid injections. Data were analyzed from May 2018 to August 2018. Interventions: Patients were randomized to injection of 80 mg methylprednisolone, 40 mg methylprednisolone, or saline. Main Outcomes and Measures: The coprimary outcomes were the symptom severity score and rate of subsequent carpal tunnel release surgery on the study hand at 5 years. Secondary outcomes were time from injection to surgical treatment, SF-36 bodily pain score, and score on the 11-item disabilities of the arm, shoulder, and hand scale. Results: A total of 111 participants (mean [SD] age at follow-up, 52.9 [11.6] years; 81 [73.0%] women and 30 [27.0%] men) were randomized, with 37 in the 80 mg methylprednisolone group, 37 in the 40 mg methylprednisolone group, and 37 in the saline placebo group. Complete 5-year follow-up data were obtained from all 111 participants with no dropouts (100% follow-up). At baseline, mean (SD) symptom severity scores were 2.93 (0.85) in the 80 mg methylprednisolone group, 3.13 (0.70) in the 40 mg methylprednisolone group, and 3.18 (0.75) in the placebo group, and at the 5-year follow up, mean (SD) symptom severity scores were 1.51 (0.66) in the 80 mg methylprednisolone group, 1.59 (0.63) in the 40 mg methylprednisolone group, and 1.67 (0.74) in the placebo group. Compared with placebo, there was no significant difference in mean change in symptom severity score from baseline to 5 years for the 80 mg methylprednisolone group (0.14 [95%CI, -0.17 to 0.45]) or the 40 mg methylprednisolone group (0.12 [95%CI, -0.19 to 0.43]). After injection, subsequent surgical treatment on the study hand was performed in 31 participants (83.8%) in the 80 mg methylprednisolone group, 34 participants (91.9%) in the 40 mg methylprednisolone group, and 36 participants (97.3%) in the placebo group; the number of participants who underwent surgical treatment between the 1-year and 5-year follow-ups was 4 participants (10.8%) in the 80 mg methylprednisolone group, 4 participants (10.8%) in the 40 mg methylprednisolone group, and 2 participants (5.4%) in the placebo group. All surgical procedures were conducted while participants and investigators were blinded to type of injection received. The mean (SD) time from injection to surgery was 180 (121) days in the 80 mg methylprednisolone group, 185 (125) days in the 40 mg methylprednisolone group, and 121 (88) days in the placebo group. Kaplan-Meier survival curves showed statistically significant difference in time to surgical treatment (log-rank test: 80 mg methylprednisolone vs placebo, P =.002; 40 mg methylprednisolone vs placebo, P =.02; methylprednisolone 80 mg vs 40 mg, P =.37). Conclusions and Relevance: These findings suggest that in idiopathic carpal tunnel syndrome, local methylprednisolone injection resulted in statistically significant reduction in surgery rates and delay in need for surgery. Trial Registration: ClinicalTrials.gov Identifiers: NCT00806871 and NCT02652390.