Comparison of an AI-based hand range of motion measurement with manual goniometry: A prospective cross-sectional pilot study in patients and healthy volunteers

Objective Manual goniometry is the standard for hand range of motion assessment but is time-consuming and requires in-person visits. This pilot study aimed to develop an AI-based measurement method and to compare its agreement with manual goniometry in both healthy volunteers and patients. Methods In this prospective cross-sectional pilot study (July 2022 to February 2023), an AI-based method was developed using six hand gestures and MediaPipe Hands. Geometric optimization was used for metacarpophalangeal and proximal interphalangeal flexion measurements. For comparison, manual goniometry was performed to evaluate measurement errors. Agreement was evaluated using the intraclass correlation coefficient (ICC) and Bland-Altman analysis. Results The study consisted of 25 healthy individuals (50 hands) and 34 patients (68 hands). The mean difference between the AI-based method and manual measurements was 0.4°±8.8°. Geometric optimization reduced the mean absolute error by 13.5° for metacarpophalangeal and proximal interphalangeal flexion measurements and by 3.5 percentage points for Swanson score. Across all parameters, the overall mean absolute error was 5.14°, root mean square error was 7.05°, and normalized RMSE was 8.7%. For the Swanson score, the method demonstrated excellent consistency (ICC: 0.95) with the manual measurements, and Bland-Altman analysis showed a narrower 95% limits of agreement after optimization (-3.5%, 7.7%) compared to the pre-optimized results (-2.4%, 13.2%). Conclusions This AI-based method showed acceptable agreement with manual goniometry for most measurements. The Swanson score measurement was clinically acceptable, but thumb movements and proximal interphalangeal flexion require further refinement. The method may serve as a supportive tool for hand function assessment, pending validation in more severe hand impairments and varied environmental conditions.