Functional Electrical Stimulation Capability Maps

Abstract

We introduce capability maps visualizing the abilities of the arm of a person with a cervical spinal cord injury activated by functional electrical stimulation (FES). We map the arm’s workspace at different wrist positions using a person-specific arm model based on force data gathered during interactions with a robot. We describe four maps: 1) a map of the maximum force the person can produce in one direction, 2) a map of wrist configurations that FES can hold against gravity and other passive forces, 3) a map of the maximum force the person can apply in all directions, and 4) a map of the directions the arm can move with FES. To demonstrate these maps we applied electrical stimulation to nine muscle groups of a person with high tetraplegia, measured the resulting force with a robot attached to the person’s wrist, created a Gaussian process regression model relating the forces to the wrist positions, and used this model to create the four capability maps. The results are 2D images displaying the arm’s force production and movement capabilities for a person with high tetraplegia as a function of wrist position. As these maps predict functional benefits of specific interventions, they can reduce risk in developing new interventions to restore function to people with whole-arm paralysis.