RoMetric: A Multi-Camera System for Accurate and Comprehensive Hand Joint ROM Evaluation

Hand joint range of motion (ROM) is a critical index for assessing hand function, quantifying disability, and guiding rehabilitation. In response to the need for objective and reliable ROM measurements, we present RoMetric, a multi-camera, non-invasive system for accurate and comprehensive hand-joint ROM evaluation. RoMetric integrates synchronized multi-view imaging, 3D joint reconstruction, and biomechanically informed angle-computation methods to overcome limitations of traditional goniometry and current vision-based approaches. The system uses four synchronized RGB cameras and a standardized seven-pose protocol to assess 15 hand joints with 20 degrees of freedom (DOFs). Validation against clinical goniometry showed strong agreement for flexion angles (ICC(3,1) = 0.75-0.91) and robust test-retest performance (mean error [ME] <5° for 80% of joints). RoMetric also yielded substantial time savings, reducing assessment duration by 87% compared with manual goniometry. Its non-invasive design enables efficient, high-precision measurements suitable for clinical and research applications.