Kinematic effects on gait of a newly designed ankle-foot orthosis with oil damper resistance: a case series of 2 patients with hemiplegia.

The ankle joint of ankle-foot orthoses (AFOs) should restrict plantarflexion to prevent foot drop during the swing phase. However, excessive plantarflexion resistance causes excessive knee flexion during the stance phase. Plantarflexion resistive moment should be easily adjustable according to the gait ability of patients with hemiplegia. Because it is difficult to adjust plantarflexion resistive moment exactly, we developed an AFO with an oil damper. It is a small shock absorber that utilizes hydraulic resistance. The oil damper generates a resistive moment to the plantarflexion rotation of the ankle joint at the initial stance phase. The magnitude of the plantarflexion resistive moment at the heel strike can be easily adjusted to accommodate each patient's condition by simply turning an adjustment screw. We used a gait analysis system to compare the gait of 2 hemiplegic patients while they were wearing either the AFO with the oil damper or the AFO with the plantarflexion stop. The AFO with the oil damper achieved sufficient plantarflexion of the ankle and mild flexion of the knee by adjusting a proper plantarflexion resistive moment during initial stance phase, and provided a more comfortable gait than did the AFOs with a plantarflexion stop.