Performance of epimysial stimulating electrodes in the lower extremities of individuals with spinal cord injury.
This study describes the performance of surgically-implanted epimysial stimulating electrodes in the muscles of the lower extremities for use in functional neuromuscular stimulation (FNS) systems for standing after spinal cord injury. A total of 86 epimysial electrodes were implanted in 13 volunteers with low tetraplegia or paraplegia receiving the Case Western Reserve University/Veteran Affairs (CWRU/VA)-implanted standing/transfer neuroprosthesis. The neuroprosthesis consisted of bilateral epimysial electrodes in the knee and hip extensors (vastus lateralis, gluteus maximus, and adductor magnus or semimembranosus) and intramuscular electrodes at the T12/L1 or L1/L2 spinal roots for trunk extension. Recruitment properties, stimulated knee and hip extension moments, standing performance, and mechanical integrity over time were measured for a period up to four years post-implantation. Stimulated thresholds were stable and recruitment was sufficient to generate joint moments adequate for standing, with up to 97% body weight supported by the legs. Four mechanical failures were observed, all in the posterior muscles of the thigh, leaving 95% of all electrodes operational at all followup intervals. Probability of 24-month survival is estimated to be 93% plateauing to a steady state of 90% at four years. These results indicate that epimysial designs are appropriate for long-term clinical use in the large muscles of the lower extremities with implanted motor system neuroprostheses.
Uhlir
James P
JP
Department of Orthopaedics, Cleveland FES Center Technical Development Laboratory, Case Western Reserve University, Cleveland, OH 44106, USA.
Triolo
Ronald J
RJ
Davis
John A
JA
Bieri
Carol
C
D000328:Adult; D004599:Electric Stimulation Therapy / Q000295:instrumentation* / Q000379:methods; D004567:Electrodes, Implanted; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000503:physiopathology; D008297:Male; D008839:Microelectrodes; D008875:Middle Aged; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000294:innervation* / Q000503:physiopathology*; D010264:Paraplegia / Q000175:diagnosis / Q000209:etiology / Q000534:rehabilitation*; D013119:Spinal Cord Injuries / Q000150:complications / Q000175:diagnosis / Q000534:rehabilitation*; D013314:Stress, Mechanical; D019415:Torque; D016896:Treatment Outcome