Combining Functional Electrical Stimulation (FES) to Elicit Hand Movements and a Mechanical Orthosis to Passively Maintain Wrist and Fingers Position in Individuals with Tetraplegia: A Feasibility Test

We have developed a new approach to assist prehension by combining functional electrical stimulation (FES) and a motorized orthosis: ORTHYB. The aim was to induce movements of fingers, thumb, and wrist joints by activating muscles using surface FES and locking joints in desired positions using electric motors, to reduce muscle fatigue and enable prolonged grasping of objects. Another hypothesis was that the mechanical orthosis would improve grip quality by constraining joint positioning and guiding movements. The functionality and acceptability of this hybrid orthosis were tested on five participants with upper-limb paralysis due to spinal cord injury. The evaluation was carried out by monitoring the quality of grip for 30 seconds on 3 different objects; perceived effort using the Borg RPE (Rating of Perceived Exertion) scale; pain using visual analog scale (VAS); acceptability using QUEST (Quebec User Evaluation of Satisfaction Technology with Assistive Technology) scale and SUS (System Usability Scale). Preliminary results indicate that the hybrid orthosis provides added value compared to FES alone. The scores obtained in terms of functionality were in most of the trials greater than or equal to those obtained with FES alone. Object grasping was possible for 30 seconds without muscular fatigue affecting grip quality.