| Description |
This research aims to develop an assistive functional electrical stimulation (FES) device to enable the tenodesis grasp in C5 spinal cord injury (SCI) patients who maintain some proximal arm function but lack hand or wrist control. The tenodesis grasp is a transformative anatomical tool in which wrist extension causes passive finger flexion, enabling individuals with C6-C7 SCI to maintain prehensile ability and manipulate objects in their environment. Unfortunately, this assistive grasp is not available to those with C5 injuries as they are unlikely to have wrist functionality. However, FES is currently being used in medical settings to reactivate paralyzed muscles through electrical stimulation with the purpose of recovering functional movement. In our work, we developed a voice-controlled FES (VC-FES) device that utilizes dual-site stimulation to evoke the tenodesis grasp. VC-FES applied to a healthy population evoked the kinematic markers of the tenodesis grasp. VC-FES applied to SCI patients restored functional grasping to the patient who previously exhibited no hand function. When VC-FES was activated by healthy participants, the wrist extended from 31.2° to -25.6°, the middle PIP joint flexed from 37.8° to 81.1°, the middle MCP joint flexed from 16.7° to 59.8°, and most notably, the distance from the tip of the middle finger to the middle MCP joint decreased from 68.1 mm to 43.4 mm. In addition, this dual-site system enabled both SCI patients to grasp a 23-mm outer diameter foam utensil grip for more than 10 seconds at a time, even allowing one patient to feed himself independently, which he could not do without VC-FES. Artificially evoking functional grasps has the potential to increase C5 SCI patients' functional capabilities, independence, and overall quality of life. The promising preliminary results shown here can help guide the design of future assistive devices meant to restore grasping capabilities for those with high-level SCIs. |
