Evaluation of the Efficacy and Robustness of a Second Generation Implantable Stimulator in a Patient With Hemiplegia During 20 Years of Functional Electrical Stimulation of the Common Peroneal Nerve

Abstract

We evaluated the efficacy and robustness of a second generation implantable stimulator for correcting drop foot (DF) in a patient with left-sided hemiplegia over 20 years of functional electrical stimulation (FES) of the common peroneal nerve (CPN). Dorsal flexion and eversion of the affected foot was partially restored by FES of the superficial region of the CPN innervating mostly the tibialis anterior (TA) and partly peroneus longus (PL) and peroneus brevis (PB) muscles. The reasons for implant failure during the long-term follow-up assessment were analyzed and resolving procedures were identified. The stimulator had an average failure rate of once every three years, due to repetitive mechanical load on the lead wires of its internal and/or external unit, and had to be serviced once per year to replace the heel switch integrated into the shoe sole. FES-associated mechanical trauma to the CPN elicited a thickening of the connective tissue around the CPN and a slightly compromised conduction velocity of the CPN. FES of the CPN, with the second generation implantable stimulator, improved gait parameters of the affected leg during the 20 years period. Long-term, daily FES enables a functional and reliable recruitment of nerve fibers, thus providing a sufficient dorsal flexion and optimal eversion of the affected foot to sustain unassisted, almost normal gait. Therefore, the presented implant is suitable for very long-term FES of the CPN.