Inter-joint coordination during manual task in myoelectric hand prosthesis users

Understanding inter-joint coordination is essential for optimizing prosthetic design and rehabilitation strategies in individuals using myoelectric hand prostheses. This study investigated upper-limb kinematic coordination during a standardized manual task in myoelectric hand prosthesis users (HPU) and healthy controls (HC). Using principal component analysis (PCA), we identified and compared primary movement patterns across the trunk, shoulder, and elbow in the two groups. Two principal components (PCs) explained approximately 90% of the total variance in both groups. The first PC, representing the primary coordination pattern, was highly similar between HPUs and HCs, with a nearly perfect positive correlation (r = 0.99). In contrast, the second PC revealed significant differences, with a large negative correlation (r = -0.70), indicating distinct secondary coordination patterns. HPUs displayed increased reliance on trunk lateral bending and shoulder ad/abduction, suggesting compensatory mechanisms to manage the control of the prosthetic device. These findings highlight the adaptive motor strategies employed by prosthesis users and the critical role of trunk and shoulder contributions in task execution. By characterizing these coordination patterns, this study provides insights into motor control adaptations in prosthesis users.