A knee and ankle flexing hybrid orthosis for paraplegic ambulation

Limitations of mechanical walking orthoses for paraplegics are high energy consumption and upper limb loading. Flexing of the knee during swing phase has been used as a means of attempting to reduce these. It has been found that this has little effect because using knee flexion results in no change in the compensatory mechanisms required for swing foot clearance. This is because knee flexion can result in an increase in effective leg length, i.e. hip to toe distance. A combination of knee flexion and ankle dorsiflexion during swing phase is suggested as a means of reducing compensatory mechanisms. To examine this hypothesis, an orthosis incorporating knee and ankle flexion was constructed. The design used a novel mechanism to link the motion of the knee to that of the ankle, and also used functional electrical stimulation. Two spinal cord-injured subjects were trained to use the orthosis in two configurations. The first configuration used knee flexion and ankle dorsiflexion and the second configuration used knee flexion alone. Kinematic data were obtained to measure the compensatory mechanisms used during gait. The results showed that a combination of knee flexion and ankle dorsiflexion during swing phase resulted in a reduction in compensatory mechanisms when compared with knee flexion alone.