Analysis of the agreement and repeatability of upper limb MediaPipe based measurements using the Bland–Altman method

Background: The shoulder joint complex is recognised for the wide range of movements it can perform and is extremely important for the performance of activities of daily living. Correct quantification of the range of motion is therefore essential in the assessment of patients with movement disorders. In this context, the universal goniometer stands out as the most widely used and economical tool, together with other technologies that have been validated in comparison with this device. Objective: This paper presents the validation of MediaPipe as a low-cost alternative tool to the universal goniometer for range of motion measurement, using a webcam as a sensor. A case study is also presented in which this tool has been implemented for the measurement and evolution of a patient’s range of motion in three rehabilitation sessions. Methods: To validate the agreement and repeatability of the MediaPipe tool, the Bland–Altman methodology was used by performing an exhaustive analysis of 360 shoulder abduction measurements for each arm in 40 volunteers, comparing them with the universal goniometer. Results: The results of the agreement analysis revealed that the mean differences between the MediaPipe and the universal goniometer for shoulder abduction were close to 0°, with limits of agreement ranging from −7.19° to 7.19° for the left arm and −6.39° to 6.39° for the right arm, indicating that the MediaPipe is valid in place of the universal goniometer. In addition, repeatability analysis showed mean differences of 0.51° for the left arm and 0.28° for the right arm, with repeatability limits ranging from −5.2° to 6.23°, suggesting reliable measurements under constant conditions. In relation to the case study, the results obtained with MediaPipe are consistent with the clinical evolution expected by the physiotherapist in shoulder injuries, considering the postoperative time and rehabilitation sessions. Conclusions: According to the results obtained, MediaPipe is a valid, reliable and low-cost tool to be used instead of the universal goniometer and can be implemented in the clinic for range of motion measurement in rehabilitation patients.