Synthesis of paraplegic gait with multichannel functional neuromuscular stimulation

Template stimulation patterns were used for a multichannel functional neuromuscular stimulation (FNS) system to synthesize movements for walking in paraplegia. Rules were developed and tested for tailoring template walking stimulation patterns to individuals. The criteria for effective rule application were based on the degree to which the paraplegic gait approached normal appearance, independence of forward progression, the least amount of upper body support, and the minimum amount of energy used as perceived by the user. The ability of preset microprocessor-controlled stimuli to generate walking in paraplegia were limited by muscle strength, fatigue, and timing of stimulation. Joint moment testing showed that paraplegic subjects had 20-60% of normal strength. In individuals at the lower end of the range, the strength was insufficient to allow independent forward progression. The muscle fatigue effected the strength and timing of joint movements during walking. Timing of hip extensor activation at heel strike was found to be critical for progression. Excessive forces were taken up through arm support, especially with hip and trunk extensor fatigue, and forward lean was essential for progression. Hip and trunk stability was achieved through stiffening by co-contraction and upper body support. This resulted in metabolic energy expenditure as high as four times normal