Effects of plantar flexion resistive moment generated by an ankle-foot orthosis with an oil damper on the gait of stroke patients: a pilot study.

Background: An ankle-foot orthosis with an oil damper was previously developed to assist the first rocker function during gait, but the effects of the amount of resistive moment generated on gait have not been clarified.

Objectives: To measure the amount of resistive moment generated by the ankle-foot orthosis with an oil damper during gait and determine its effect on the gait of patients with stroke.

Study Design: Preliminary cross-sectional study.

Methods: The gait of four patients with stroke in the chronic phase was measured in four conditions: without an ankle-foot orthosis and with the ankle-foot orthosis with an oil damper generating three different amounts of resistive moment. Measurements were taken with a three-dimensional motion analysis system and a specially designed device to determine the resistive moment.

Results: The resistive moment was observed in the former half in stance of the paretic limb, and its magnitude was less than 10 N m. Some gait parameters related to terminal stance and preswing were affected by the amount of resistive moment. The forward component of floor reaction force and the shank vertical angle showed peak values when the patients reported feeling most comfortable during gait.

Conclusion: Although the resistive moment generated by the ankle-foot orthosis with an oil damper was small, it was sufficient to alter gait.

Clinical Relevance: To maximize the effectiveness of ankle-foot orthoses, it is necessary to know the effects of resistive moment on the gait of patients with stroke. The ankle-foot orthosis with an oil damper assists the first rocker function in gait and also affects the gait in a later phase in stance. The peak values of some gait parameters coincided with patients reporting gait to be most comfortable. It is important to know that ankle-foot orthosis with an oil damper assistance in the first rocker alters the weight acceptance on the paretic limb and affects the gait parameters related to propulsion ability in stance.