Volume Effect of Nerve Hydrodissection for Carpal Tunnel Syndrome

Objectives This study compared ultrasound‐guided nerve hydrodissection (HD) outcomes using two commonly used injectate volumes (10 and 5 mL) of normal saline to explore if there is a volume effect of HD for patients with moderate carpal tunnel syndrome (CTS). Methods Twenty‐four participants were randomly assigned to treatment with HD using ultrasound‐guidance and either 10 mL or 5 mL of normal saline (HD‐10 and HD‐5 groups respectively). Our primary outcome measures were the change scores of the two subscales of the Boston Carpal Tunnel Syndrome Questionnaire: The Symptom Severity Scale (SSS) and Functional Status Scale (FSS). We conducted a one‐way repeated analysis of variance for 3 time points (4, 12, and 24 weeks) for both SSS and FSS, respectively, for change scores from time 0, and percentage change from time 0. Results All participants (n = 12 per group) completed the study. From 0 to 24 weeks the HD‐10 group outperformed the HD‐5 group for improvement in SSS (median ± IQR; −0.8 ± 0.4 versus −0.5 ± 0.5; P = .024) and FSS scores (mean ± SD; −0.8 ± 0.2 versus −0.5 ± 0.5; P = .011). The HD‐10 group improvement in FSS subtest significantly exceeded the MCID percentage‐change‐based threshold of 27% (34%; P = .039). Conclusions Despite the limitations of small study size, a largely inert injectate, and a single injection approach, these findings in favor of the 10 mL group suggest that the volume used for ultrasound‐guided HD in moderate CTS matters, and a higher volume is more effective.