Characterization of Upper Extremity Joint Angle Error for Virtual Reality Motion Capture Compared to Infrared Motion Capture

Virtual reality (VR) offers built-in wearable sensor-based tracking capabilities. Current research focusses on position and orientation error, with limited results on more clinically relevant metrics, such as joint angles. This leads us to our first objective, to characterize the accuracy of upper extremity VR motion capture. Since the intent is for clinical translation, our second objective is to compare the errors across people identified as healthy controls and people who had experienced a spinal cord injury (SCI). Spatially and temporally synced VR and infrared motion capture data were collected during a variety of custom VR Beat Saber levels. Error values were found with infrared motion capture as the ground truth. The median RMSE was found to be below 7° for shoulder horizontal adduction and elbow flexion and 5° for shoulder elevation and wrist joint metrics. The percentage median error for the range of motion was found to be below 30%, 15%, and 5% for the frontal wrist, sagittal wrist, and all other joints, respectively. Larger standard deviations suggest that repetitions are needed to obtain reliable measurements. No statistical difference in any error metric was found between the control cohort and SCI cohort, providing evidence for clinical translation for post-SCI treatment.