Is a steroid injection clinically effective in reducing symptoms and improving function in the short to medium term compared to a night splint in mild to moderate carpal tunnel syndrome managed in primary care?

Problem

Carpal tunnel syndrome (CTS) is an entrapment neuropathy of the median nerve at the carpal tunnel with high consultation rates in primary care. Patients with mild-moderate CTS are commonly treated with night splints and/or corticosteroid injection. The comparative effectiveness of these interventions has not been reliably established. Our primary objective was to investigate whether a corticosteroid injection is effective in reducing symptoms and improving hand function in mild-moderate CTS over 6 weeks compared with a night resting splint.

Approach

A multicentre, randomised, parallel-group, pragmatic clinical trial in adults aged ≥18 years with mild-moderate CTS diagnosed by standard clinical assessment. Participants were recruited from GP practices or primary-secondary care musculoskeletal interface clinics and randomised (1:1) to receive either a single carpal tunnel injection of 20mg methylprednisolone acetate or a night splint to be worn for 6 weeks. The primary outcome was the Boston Carpal Tunnel Questionnaire (BCTQ) overall score at 6 weeks. Secondary outcomes included; BCTQ symptom severity and function subscales, pain intensity, insomnia due to wrist pain, prescribed pain medication and referral for surgery. Participants were assessed at baseline, 6 weeks and 6 months. The primary analysis was by intention-to-treat (ITT) with multiple imputation for missing data. A sample size of 120 per group was required to detect a 15% greater improvement in BTCQ overall score at 6 weeks for injection compared with night-splint (Baseline BCTQ 2.9, between-group difference 0.45 (pooled SD 1.0), 90% power, 5% two-tailed significance, 15% loss-to-follow-up).

Findings

From 25 recruiting sites, 234 participants were randomised, (splint n=118, injection n=116), of whom 212 (90.6%) completed 6-week primary outcome data. The overall BCTQ score was better at 6 weeks in the injection arm compared with the splint arm (mean 2.02 vs. 2.29; adjusted mean difference (MD) -0.32 (95% confidence interval (CI) -0.48, -0.16)). Adjusted effect estimates for symptom severity (MD -0.35 (-0.53, -0.17)); functional status (-0.26 (-0.43, -0.09)); pain intensity (-0.97 (-1.64, -0.30)) and insomnia (odds ratio (OR) 0.44 (0.22, 0.87)) at 6 weeks also favoured injection. At 6 months, there were no significant differences between treatments in overall BCTQ score MD 0.06 (-0.11, 0.23); symptom severity MD 0.13 (-0.07, 0.33); hand function MD <0.01 (-0.18, 0.17); pain intensity MD 0.79 (-0.02, 1.59); insomnia OR 1.12 (0.55, 2.20); prescribed analgesics OR 1.99 (0.70, 5.66) or surgical referral OR 1.66 (0.73, 3.77). Health economic data will be presented.

Consequences

In mild/moderate CTS, a single corticosteroid injection led to significantly better improvements at 6 weeks in hand symptoms, pain and function, as well as a range of secondary outcomes, compared with a night-resting splint. Within-group differences were similar at 6 months although there were no significant between-group differences. Our findings suggest that injection provides more rapid improvement in clinical outcomes in CTS. Long-term (24-month) follow-up is nearing completion.