Clinical use of percutaneous intramuscular electrodes for functional electrical stimulation

Objective: To evaluate the clinical use of the percutaneous intramuscular electrode in functional electrical stimulation (FES). Design: Randomized and controlled study. Setting: A referral center and institutional practice providing outpatients (12 men, 5 women) who had implanted percutaneous intramuscular electrodes for more than 1 year examined. The average follow-up time after implantation of electrodes was 2.2 years (range, 1yr to 4yr 10mo). Overall, there were 327 electrodes (83 upper extremities and 244 lower extremities). Intervention: The indwelling electrode was composed of helically coiled Teflon-coated rope stranded from 19 hard drawn wires of SUS 316L stainless steel (SES 114). Main Outcome Measures: The rates of breakage, movement, and infection, and the number of electrodes that needed reimplantation were evaluated. Results. Only one electrode broke (0.3%) in the iliopsoas muscle at 12 weeks after implantation. Eight electrodes (2.4%) were removed because of loss of sufficient contraction force caused by movement of the electrodes. Movements occurred at 9 weeks in 6 electrodes and at 5 months in two. The failure rate of electrodes in the lower extremities was 3.7%. No failures occurred in the upper extremities. Ten electrodes (3.1%) required reimplantation. Although ten superficial infections (3.1%) were seen around the site of electrode insertion, no removals of electrode were needed. All electrodes in one patient were removed, however, because of generalized methicillin-resistant Staphylococcus aureus infection complicated with renal disease. Electrodes were reimplanted after improvement of the infection. Conclusions: The ultrafine percutaneous intramuscular electrode was considered practical for long-term FES use.