UC San Diego

Spasticity is an involuntary velocity and muscle-length-dependent increase in muscle tone that is a debilitating symptom of multiple acquired and inherited neurological disorders. It impairs the function of the hand, resulting in a decreased quality of life. To aid individuals with spasticity, this work developed a soft-robotic orthosis that assists the thumb in achieving movement in three degrees of freedom (DOF). It assists in the extension of the interphalangeal joint, the combined extension of the metacarpal and carpometacarpal joints, and the abduction of the carpometacarpal joint. Individual assistance of these joints was achieved using three unfolding textile pneumatic actuators. These actuators were tested on a 3D-printed bio-inspired test bed with integrated torsional and linear springs to emulate spasticity. The orthosis met the full range of motion targets for each joint and surpassed the threshold required for each joint to be used in activities of daily living. The orthosis was also capable of providing assistance to each DOF independently, came very close to reaching a pre-selected target point on the test bed, and, when tested on a healthy individual, could also provide independent joint assistance for each DOF. This research provides a tool to study whether individualized joint assistance during rehabilitation improves patient outcomes. In addition, by showcasing the ability of a soft-robotic orthosis to assist movement in simulated spasticity of individual thumb joints, it provides a paradigm for applying soft-robotic approaches to rehabilitation in individuals living with conditions such as stroke, spinal cord injury, or cerebral palsy.