A hybrid orthosis for paraplegic standing with percutaneous electrodes

The authors have used instrumented supracondylar knee-ankle-foot orthoses (SKAFOs) and feedback-controlled surface muscle stimulation to help spinal-cord-injured patients stand and walk for prolonged periods. Such a combination of instrumented orthoses and functional neuromuscular stimulation (FNS) is referred to as hybrid orthotics. A similar use of SKAFOs and an on-off (bang-bang) controller is being applied to a research subject using muscles implanted with percutaneous wire electrodes. A T-8-level incomplete paraplegic subject with previously implanted percutaneous intramuscular electrodes was fitted with a pair of lightweight orthoses fabricated using carbon-fiber composite. Commercial strain gages were mounted on the brace uprights above the knee joint. Measurements from these gages provided an estimate of the direction and magnitude of the knee-extending moment due to the ground reaction force resisted by the brace, when the subject's knees were in extension. In preliminary laboratory trials with this controller, the subject was able to stand for prolonged periods with little or no stimulation to the quadriceps while the braces provided support.<
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