Clinical experience with reinforced, anchored intramuscular electrodes for functional neuromuscular stimulation.
Implanted intramuscular electrodes must remain functional for many years if functional neuromuscular stimulation (FNS) is to become a standard treatment in paralysed individuals. In initial trials we found that 5 of 11 coiled single-wire FNS electrodes implanted in 3 patients failed within 8 months. Consequently, we turned to a reinforced electrode comprising 2 multi-stranded, insulated wires tandem-wound on a prolene core and terminated by a prolene anchor or tine (after Mortimer et al., 1986, 1987). The electrodes were implanted with a translumbar aortogram needle, the teflon sheath of which enabled us to stimulate through the tip to guide placement. We have monitored the electrical and functional properties of 8 reinforced electrodes implanted in 2 incomplete quadriplegic patients over 22 months. Four of the electrodes were used for at least 1 h daily to exercise muscles or to provide FNS in gait. Electrical impedances, thresholds and elicited limb motion remained constant in all 8 electrodes over the test period. Disadvantages of the reinforced electrodes are (1) difficulty of eventual removal, and (2) risk of pathogenic infiltration is increased by the 3-filament structure (fortunately dense tissue encapsulation seems to mitigate infection). We conclude that tandem-wound, prolene-reinforced FNS electrodes are much more robust than previous single-coil designs and may form the basis for FNS devices of the future.
Prochazka
A
A
Division of Neuroscience, University of Alberta, Edmonton, Canada.
Davis
L A
LA
D000328:Adult; D000758:Anesthesia; D000818:Animals; D002417:Cattle; D004553:Electric Conductivity; D004558:Electric Stimulation; D004563:Electrochemistry; D004567:Electrodes, Implanted; D005260:Female; D006429:Hemiplegia / Q000503:physiopathology / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D009132:Muscles / Q000502:physiology; D009469:Neuromuscular Junction / Q000502:physiology*; D010243:Paralysis / Q000503:physiopathology / Q000628:therapy*; D011782:Quadriplegia / Q000503:physiopathology / Q000628:therapy; D013552:Swine