Voice-Controlled Dual-Site Functional Electrical Stimulation Enables Tenodesis Grasping

Patients with high-level spinal cord injuries (SCIs) that maintain wrist movement but lack the ability to close the hand volitionally may preserve some degree of hand function by using the tenodesis grasp. The tenodesis grasp consists of extending the wrist to passively shorten the finger flexors, resulting in the fingers closing. However, the tenodesis grasp is unavailable to patients who lack wrist function. To address this, we developed a voice-controlled, dual-site, functional electrical stimulation system that evokes the tenodesis grasp by stimulating the wrist extensors and finger flexors simultaneously. The system’s ability to evoke the tenodesis grasp was validated by measuring the hand kinematics in a healthy population and then evaluated with a C5 SCI patient for functionality. We demonstrate that the system reliably closed the healthy participant’s grasp. The distance from the tip of their middle finger to their metacarpophalangeal joint was approximately 70 mm at rest and decreased to 45 mm when stimulated. We also show that an SCI participant with no strength in their hand or wrist was able to grasp and hold an eating utensil with the system’s assistance. This work is an important step towards wearable assistive devices that can return the ability to grasp to C5 SCI patients.Clinical Relevance—This assistive device can restore hand function and independence to individuals with a C5 spinal cord injury.