Understanding Technology-Induced Compensation: Effects of a Wrist-Constrained Robotic Hand Orthosis on Grasping Kinematics

Robotic hand orthoses have the potential of supporting grasp function of people with sensorimotor impairments. To achieve lightweight and simple solutions, most devices focus on supporting only a subset of the functional abilities of the hand. This study investigates the effect of such a design trade-off in a wrist-constrained robotic hand orthosis and its effects on upper limb kinematics and grasping abilities of seven able-bodied subjects. Using wearable, inertial sensors on hand, arm, and shoulder we quantified how a reduction of degrees of freedom affected movement strategies in eleven grasping tasks. This analysis helps to understand how simplified design solutions may affect movement patterns of the target end-users, depending on their residual level of functionality. Also, this further highlights the issue of usability-related design trade-offs between compact and lightweight solutions, and more complex multi-degree of freedom devices.