Wrist and Thumb Kinematics During Sustained Smartphone Typing in Patients with Carpal Tunnel Syndrome: A Cross-Sectional Comparative Study

Objectives: Carpal tunnel syndrome (CTS) is associated with impaired hand sensorimotor function, but wrist and thumb kinematics during sustained smartphone use remain unclear. This study compared joint posture, angular velocity, and time-related kinematic changes during a 30-min smartphone typing task between patients with CTS and healthy controls. Methods: Thirteen patients with CTS and 14 healthy controls completed a standardized 30-min two-handed smartphone typing task. Three-dimensional wrist and thumb kinematics were recorded, and mean joint angles and root mean square (RMS) angular velocities were calculated for wrist extension, wrist ulnar deviation, thumb metacarpophalangeal (MCP) flexion, MCP abduction, and interphalangeal (IP) flexion. Outcomes were analyzed over the entire task and across three 10-min intervals. Results: The CTS group showed greater wrist extension than the healthy control group (39.27 ± 9.31° vs. 27.99 ± 9.92°, p = 0.005) and less thumb MCP flexion (25.94 ± 8.43° vs. 32.66 ± 6.50°, p = 0.028). No significant between-group differences were found for the other joint angles or RMS angular velocities. No significant time effects or group × time interactions were observed. Conclusions: Patients with CTS demonstrated greater wrist extension and reduced thumb MCP flexion during sustained smartphone typing. These findings suggest that CTS-related kinematic differences may be more apparent in specific joint postures than in overall movement velocity.