Restoration of elbow extension via functional electrical stimulation in individuals with tetraplegia

Abstract

Functional electrical stimulation of the triceps is a method of restoring elbow extension to individuals with paralyzed triceps. Eleven arms of individuals with cervical-level spinal cord injuries (SCIs) received a triceps electrode as an addition to a hand-grasp neuroprosthesis. Stimulation was controlled either as part of a preprogrammed pattern or via a switch or an accelerometer that was connected to the neuroprosthesis external controller. The outcome measures were (1) elbow extension moments at different elbow positions, (2) performance in controllable workspace experiments, and (3) comparison to an alternative method of providing elbow extension in these individuals--a posterior deltoid (PD) to triceps tendon transfer. Stimulated elbow extension moments in 11 arms ranged from 0.8 to 13.3 N.m. The stimulated elbow extension moments varied with elbow angle in a manner consistent with the length-tension properties of the triceps. Triceps stimulation provided a significantly stronger elbow extension moment than the PD to triceps tendon transfer. The elbow extension moment generated by the tendon transfer and triceps electrode being activated together was always greater than either method used separately. Stimulation of the long head of the triceps should be avoided in persons with weak shoulder abduction, since the long head adducts the shoulder and limits shoulder function in these cases. Statistically, elbow extension neuroprostheses significantly increased the ability to successfully reach and move an object and significantly decreased the time required to acquire an object while reaching.