A study of the feasibility of using nerve cuff signals as feedback for maintenance of posture in paraplegic subjects

Standing in paraplegics can be restored using Functional Electrical Stimulation (FES) to activate paralyzed muscles below the spinal cord lesion. However, reliable balance control with FES will also require sensory feedback. Suitability of electroneurographic (ENG) signals from nerve cuff electrodes as feedback for controlling FES was studied in awake swine during postural sway. Tibial nerve ENG signals were recorded using implanted amplifiers, and pressure distribution under both hind feet was simultaneously monitored. Comparisons were made between pressure changes under the feet of swine and human subjects. During human sway in eight directions, average pressure in loaded foot-sole regions increased by 72+24%. In swine subjects, comparable pressure changes were detected from the ENG signals with 94% accuracy, and 84% of all swine postural sway events were detectable from ENG signals. Results from this study suggest that closed-loop control of paraplegic posture using nerve signals to monitor center-ofpressure displacements may be feasible.