Purpose: Measuring range of motion (ROM) in the wrist joint is an essential part of hand and wrist functional evaluations, especially before and after surgery. However, accurate measurements require experience and time. To reduce patient and surgeon burdens related to ROM measurement, a smartphone-based system, which enables participants to measure the ROM of the wrist joint semiautomatically using self-taken pictures on a smartphone, was developed and evaluated in this study. Methods: In the developed system, participants were asked to take a picture of their wrist by using the other hand to position the joint first into full flexion and then into full extension. The hand and arm regions were automatically extracted in the program, and the ROM was estimated after the area of the hand and forearm was cropped. To verify the accuracy of ROM measurements in this system, the proposed method was tested on 66 images of hands from 33 participants; measurements were compared with those taken by hand surgeons. A limit of agreement and an intraclass correlation coefficient (ICC) were used for evaluation. Results: The smallest averages (95% limits of agreement) of flexion and extension were 11.32° (95% confidence interval [CI], 8.88° to 13.76°) and 11.01° (95% CI, 8.64° to 13.39°), respectively. The ICC (1,1) for 3 measurements taken by one assessor was 0.99 (95% CI, 0.986–0.992), and the ICC (2,1) for 2 measurements taken by both assessors was 0.97 (95% CI, 0.947–0.977). Conclusions: In this study, we developed a system to measure the semiautomatic ROM of the wrist joint using a smartphone image. Its accuracy was within a clinically usable error range that was comparable with that of a hand surgeon. Clinical relevance: This system can reduce the burden of ROM measurement for both patients and doctors.
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