P143 The clinical and cost-effectiveness of corticosteroid injection versus night splints for carpal tunnel syndrome: 24-month follow-up of an open-label, parallel group, randomised controlled trial

Abstract

Background: Patients with mild-to-moderate carpal tunnel syndrome (CTS) are commonly treated with night splints and/or local corticosteroid injection. In the INSTINCTS (INjection versus SplinTing in Carpal Tunnel Syndrome) trial, we previously reported that a single corticosteroid injection is more effective than night splinting at 6 weeks but not at 6 months. The aims of follow-up at 12 and 24 months were to examine whether corticosteroid injection is clinically and cost-effective in reducing symptoms in the longer-term compared to night splinting and to compare rates of CTS surgery. Method(s): INSTINCTS was a pragmatic clinical trial in adults >=18 years with mild-to-moderate CTS diagnosed using standardised clinical criteria. Participants were recruited from primary care or musculoskeletal interface services and randomised 1:1 to receive either a single carpal tunnel injection of 20mg methylprednisolone acetate or a night splint. Follow-up questionnaires were mailed at 6 weeks and 6, 12 and 24 months. Key clinical outcomes at 12 and 24 months were the Boston Carpal Tunnel Questionnaire (BCTQ), hand/wrist pain intensity (0-10 numeric rating scale (NRS)) and the number of patients referred for and receiving CTS surgery. Longitudinal mixed effect models were fitted to estimate overall treatment effect at each time point by including interaction terms between treatment and time, adjusted for age, gender, symptom duration and baseline score. The cumulative number (%) of participants i) referred or ii) undergoing CTS surgery were examined by treatment group. Cost-utility analysis was conducted from an NHS perspective to determine the cost-effectiveness of injection versus night splinting. Result(s): 118 participants were randomised to night splinting and 116 to corticosteroid injection. In the splint group, 88 (78%) and 81 (74%) completed follow-up at 12 and 24 months respectively compared to 87 (77%) and 78 (72%) in the injection group. There were no statistically significant differences between splint and injection groups in BCTQ score at 12 (adjusted mean difference -0.09; 95%CI -0.30, 0.12) or 24 months (0.06; -0.16, 0.28) or hand pain NRS (12 months 0.03; -0.79, 0.85. 24 months 0.41; -0.45, 1.26). By 24-month follow-up, a greater proportion of the injection group had been referred for (28% vs 20%) and undergone (22% vs 16%) CTS surgery than the splint group. Injection was more costly (mean difference 68.59 (-120.84, 291.24)) with lower quality-adjusted life-years (QALYs) than splinting over 24 months (mean difference -0.022 (-0.074, 0.024)). Conclusion(s): To our knowledge, this is the longest-reported follow-up of a randomised trial investigating the conservative management of CTS, with the largest sample size. Over 24-months, there were no differences in symptoms between groups and injection was not costeffective compared with splinting. Surgical referral and intervention rates were low overall, but slightly more frequent in the injection group.