Performance of epimysial stimulating electrodes in the lower extremities of individuals with spinal cord injury

Abstract

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.

Effects of Stimulating Hip and Trunk Muscles on Seated Stability, Posture, and Reach After Spinal Cord Injury

“…All participants received IM stimulating electrodes [21] inserted bilaterally at L1-L2 spinal nerves to recruit lumbar erector mass for trunk extension [14,22,23]. All subjects also received IM or epimysial electrodes [24] to activate gluteus maximus bilaterally for hip extension [25]. Stimulation of semimembranosus was utilized in one volunteer (S7) with a non-functional gluteus maximus electrode, and two subjects (S1,S5) had IM electrodes at the spinal nerves of T12-L1 to activate quadratus lumborum for medial-lateral stability.…”

Functional electrical stimulation after spinal cord injury: current use, therapeutic effects and future directions

“…Fortunately, guidelines for safe stimulation have been developed and these electrodes have been used successfully in many applications, such as control of bladder, phrenic nerve for breathing, peripheral nerve stimulation for pain control, and cranial nerve stimulation for epilepsy suppression. Epimysial electrodes generate minimal damage and have proven to be durable for upper and lower limb applications, 20,21 but for activation of deep and very small muscles, intramuscular electrodes are preferable.…”

Effects of Intramuscular Trunk Stimulation on Manual Wheelchair Propulsion Mechanics in 6 Subjects With Spinal Cord Injury

“…All subjects had also received intramuscular or epimysial stimulating electrodes [34] to activate gluteus maximus bilaterally for hip extension [35]. Hamstrings (semimembranosus) were utilized to control the pelvis in one volunteer (S5) with a non-functional gluteus electrode, and one subject (S3) had intramuscular electrodes at T12-L1spinal nerves to activate quadratus lumborum for medial-lateral stability.…”