Effect of a Gravity-Compensating Orthosis on Reaching After Stroke: Evaluation of the Therapy Assistant WREX

Abstract

Iwamuro BT, Cruz EG, Connelly LL, Fischer HC, Kamper DG. Effect of a gravity-compensating orthosis on reaching after stroke: evaluation of the Therapy Assistant WREX. Objective To evaluate the effectiveness of an upper-extremity orthosis to improve the reaching workspace of stroke survivors. Design Within-subjects repeated-measures design evaluating reaching with and without the Therapy Assistant Wilmington Robotic Exoskeleton (WREX). Setting Laboratory. Participants Stroke survivors (N=10) with chronic upper-extremity hemiparesis. Interventions Not applicable. Main Outcome Measures Arm movement kinematics (Optotrak Certus motion detection system), muscle activity for biceps, triceps, anterior deltoid, and brachioradialis muscles (bipolar surface electromyography). Results Significant improvements of reaching distance occurred for all subjects across all targets ( P<.001) when using the Therapy Assistant WREX. While the self-selected peak speed of hand movement during the reach decreased significantly with the Therapy Assistant WREX ( P<.001), use of the Therapy Assistant WREX led to improved quality of movement as signified by a decrease in jerk ( P<.001) and a shift in the timing of the peak speed to an earlier point in the movement ( P<.001). Electromyographic muscle activity analysis showed that use of the Therapy Assistant WREX led to a reduction in biceps activity across all targets during the reach ( P<.05), in conjunction with a marginally significant reduction in activity of the anterior deltoid ( P<.055). No changes were observed in triceps ( P=.47) or brachioradialis activity ( P=.28). Conclusions By reducing requirements for shoulder activation, the Therapy Assistant WREX improved reaching performance among stroke survivors compared with free reaching, thereby potentially facilitating practice of functional tasks.