The Mdial system for reconstruction of paraplegic locomotion - its development and refinement using virtual axis and motor power assist

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We have been developing the orthotic system called the medial system for reconstruction of paraplegic standing and walking. This system consists a medial single hip joint (MSH) and bilateral knee-ankle-foot orthoses and overcomes the orthotic demerits of bulkiness and tightness in daily using.1. For refinement of this stem we developed a new hip joint having virtual axis by sliding mechanism. This modified MSH system was compared to the original MSH system in the gait function of 5 paraplegic patients. Cadence, stride, and velocity with the modified MSH system were always higher than with the original MSH system. The preferable height of the virtual axis was 60mm over the perineum in all patients except for one. In walking with the modified MSH we identified reduced pelvic rotation, whereas larger stride.2. For overcoming the passivity problem of orthotic approach, we added motor power assist to the modified MSH system. Simple On/Off switching for control was adopted. In all of investigated three paraplegic cases, HR change in walking was smaller with powered orthosis than with non-powered one, however velocity was slower with powered orthosis than with non-powered one. For solving a problem of low velocity walking, we improved hip joint angular velocity from 15 to 50 degrees per second.3. For further refinement of the modified MSH, we added hinge mechanism to the joint permitting abduction and adduction ranging of 10 degrees. With this mechanism patients seemed to turn easier than without it.