Implantation techniques and experience with percutaneous intramuscular electrodes in the lower extremities

Area of Science:

• Biomedical Engineering
• Rehabilitation Medicine
• Neuroscience

Background:

• Paraplegic individuals often require assistive devices for mobility.
• Selective muscle stimulation can potentially restore functional gait.
• Existing neuro-orthotic systems face challenges with electrode durability and function.

Purpose of the Study:

• To evaluate the efficacy and reliability of temporary percutaneous intramuscular electrodes for gait restoration in paraplegic subjects.
• To assess electrode failure modes and their impact on functional outcomes.
• To explore the potential for iterative system improvement through electrode revisions.

Main Methods:

• Implantation of fine wire electrodes at motor points of key leg muscles in paraplegic subjects.
• Daily electrical stimulation for exercise and gait training (approx. 12 hours/week).
• Monitoring electrode failures due to breakage (high impedance) or movement, and performing revisions.

Main Results:

• 35% of 1025 implanted electrodes failed within the first 4 months, primarily due to movement (over 75% of early failures).
• Electrode failure probability decreased exponentially, reaching <4% per month for electrodes implanted >6 months.
• Successful electrode withdrawal was generally possible, facilitating system revisions.

Conclusions:

• Percutaneous intramuscular electrodes offer a viable method for selective muscle stimulation to improve gait in paraplegia.
• Electrode movement is a significant factor in early-stage failures, necessitating careful implantation and potential design improvements.
• The ability to revise the neuro-orthotic system through electrode replacement enhances its long-term functional potential.