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A Pneumatically Powered Knee-Ankle-Foot Orthosis (KAFO) With Myoelectric Activation and Inhibition

By Sawicki, Gregory S.; Ferris, Daniel P.; Journal of NeuroEngineering and Rehabilitation, Vol. 6, No. 23
Publication Date: 2009

Study tested the mechanical performance of a prototype knee-ankle-foot orthosis (KAFO) powered by artificial pneumatic muscles during human walking. The unilateral powered KAFO was an extension of a previously built and tested lightweight carbon fiber ankle-foot orthosis (AFO) and featured antagonistic pairs of artificial pneumatic muscles at both the ankle and knee. The orthosis muscles were controlled using surface electromyography recordings from the user’s own muscles. Study participants, three males without disabilities, were fitted with custom KAFOs equipped with artificial pneumatic muscles to power ankle plantar flexion/dorsiflexion and knee extension/flexion. Participants walked over ground at 1.25 meters per second under four conditions without extensive practice: (1) without wearing the orthosis; (2) wearing the orthosis with artificial muscles turned off; (3) wearing the orthosis activated under direct proportional myoelectric control; and (4) wearing the orthosis activated under proportional myoelectric control with flexor inhibition produced by leg extensor muscle activation. Joint kinematics, ground reaction forces, electromyography, and orthosis kinetics were collected. The KAFO produced about 22 to 33 percent of the peak knee flexor moment, about 15 to 33 percent of the peak extensor moment, approximately 42 to 46 percent of the peak plantar flexor moment, and approximately 83 to 129 percent of the peak dorsiflexor moment during normal walking. With flexor inhibition produced by leg extensor muscle activation, ankle and knee joint kinematic profiles were more similar to the without-orthosis condition compared to when there was no flexor inhibition. The proportional myoelectric control with flexor inhibition allowed for a more normal gait than direct proportional myoelectric control.
Published by: BioMed Central Ltd   (Website:http://www.biomedcentral.com)

Link to text: http://www.jneuroengrehab.com/content/6/1/23
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