抄録
Ankle foot orthosis (AFO) assists the gait motion of persons with disability such as of hemiplegia, and the biomechanical function is the primary concern of AFO. In conventional prescription of AFO, the attention has been mainly focused on the ankle joint support at a secure position against the stumbling due to toe contact with floor during the swing phase of gait cycle, but little attention has been paid for its function during the stance phase. In this study, the mechanical characteristics of shoehorn-type AFO is examined in the context of the gait motion analysis during the stance phase of normal subjects, and by experimental analysis of the ankle joint stiffness in sagittal plane on a universal testing machine. Deformation of AFO is characterized by the relative angle between the shank and foot planes, and it is found that the stiffness of AFO depends strongly on the foot angle. The joint moment during the stance phase is evaluated for slow-speed gait with and without AFO. It is found that the knee extension moment of the gait with AFO is significantly larger than that without AFO. It is expected that the ankle joint constraint imposed by AFO results in a gait pattern different from the normal, although the resisting moment of AFO is not so significant in the joint moment.
