Electrode characterization for functional application to upper extremity FNS

A quantitative method has been developed to characterize the isometric vectors of electrically simulated paralyzed muscles of the thumb. The vectorial force output as a function of the stimulus level was measured for individual electrode/muscle combinations in a number of intramuscular and epimysial electrodes implanted in paralyzed thenar of cervical-level spinal-cord-injury subjects. Vectors were used to determine the output characteristics of each electrode/muscle combination. The characteristics studied included the strength of the contraction, the stimulus level at which fibers from other muscles are stimulated, the recruitment gain of force, dependency of the output on the skeletal position, and the direction of force produced.