Ergonomically designed arch-integrated hand orthosis for computer typing to reduce the risk of carpal tunnel syndrome.

Abstract

Background: Conventional wrist-hand-orthoses are commonly prescribed for the conservative management of carpal tunnel syndrome; however, the intrinsic structural arches of the hand, particularly the proximal transverse and longitudinal arches, are generally not considered in orthotic design. Insufficient support of these arches during typing may alter force transmission and increase compensatory muscle activity.

Purpose: To evaluate the immediate effects of an arch-integrated wrist-hand-orthosis on thumb abductor and finger extensor muscle activity during typing in individuals with carpal tunnel syndrome and compare its performance with a commercially available wrist-hand-orthosis.

Study design: Cross-sectional study with a randomized repeated-measures crossover evaluation of orthotic interventions.

Methods: Forty healthy controls and forty individuals with clinically diagnosed carpal tunnel syndrome were recruited. Participants completed a standardized typing task under three randomized conditions: without an orthosis, with a developed arch-integrated wrist-hand-orthosis, and with a commercially available wrist-hand-orthosis. Surface electromyography was recorded from the thumb abductor and finger extensor muscles. Mean amplitude, integrated activity, and signal variability were analysed. Between-group comparisons used the Mann-Whitney U test, whereas orthotic effects were evaluated using Friedman and Wilcoxon signed-rank tests with effect sizes and 95% confidence intervals.

Results: Compared with healthy controls, individuals with carpal tunnel syndrome demonstrated significantly greater muscle activity (p < 0.05), indicating increased neuromuscular demand during typing. The developed arch-integrated wrist-hand-orthosis significantly reduced electromyographic amplitude, integrated activity, and signal variability compared with the no-orthosis condition, with moderate-to-large effect sizes (p < 0.05). In contrast, the commercially available wrist-hand-orthosis produced inconsistent or non-significant effects. Typing speed was maintained with the developed orthosis but declined with the commercially available orthosis.

Conclusions: Preserving the proximal transverse and longitudinal hand arches while supporting the wrist reduced muscular demand and promoted more stable muscle recruitment during typing in individuals with carpal tunnel syndrome. These findings support task-specific, biomechanically informed orthotic design, although the results represent immediate laboratory-based rather than long-term clinical effects.