Multi-Channel Functional Electrical Stimulation to Improve Specificity of Hand Extension.

The long-term goal of this research is to improve the functionality of non-invasive transcutaneous functional electrical stimulation (FES) by improving specificity in upper extremity paralysis. Spinal cord injuries result in an estimated 10,000 new cases of upper extremity paralysis yearly. FES has been used extensively to assist and rehabilitate individuals with lower-limb paralysis, but it has not been widely adopted for upper-limb paralysis. This is in part due to the complex setup necessary to target the right combination of small muscles densely packed in the forearm to create a desired hand gesture. To address this challenge, here we introduce a new multichannel FES system that enables complex current steering with a high compliance voltage to selectively recruit small extrinsic hand muscles in isolation or in combination. Using this system with real-time motion capture data of the hand, we stimulated unique electrode configurations each second to rapidly identify a rich repertoire of hand gestures. Additionally, as an initial demonstration of the unique current steering capabilities, we show that FES involving three active electrodes, instead of the traditional 2-electrode setup, provides greater specificity and redundancy, which in turn could support more therapeutic motions and interleaved stimulation to reduce fatigue Thus, this work constitutes an important step towards more efficient, dexterous, and robust upper-limb FES to improve neurorehabilitation outcomes for people with spinal cord injuries.Clinical Relevance- A new multichannel FES system can rapidly configure FES stimulation to evoke a variety of single-digit and multi-digit hand gestures.