[Quantitative analysis of lateral force of floor reactions in normal and above-knee prosthetic gait]

Analysis of the lateral force of floor reactions has only been reported with reference to the vertical and fore- and-aft force because of large individual variations and great differences between the right and left limb of the same individual on the normal pattern of the force curve. In this study, the lateral force in normal and above-knee prosthetic gait was evaluated by calculating the total impulse during stance phase duration as well as by characteristic points of the force curve. The sensitivity of the electronic unit connected to the Kistler 's force plate was enhanced four times. The following results were obtained: In normal gait, the lateral stability during stance phase was shown by the lateral force which was proved to be a regulative element for rhythmical forward movement of the center of gravity of the body. The lateral stability in above-knee prosthetic gait was evaluated not only by the characteristic pattern of the force curve, but also by a decreased difference of the impulse of lateral force between the natural and artificial limb. The initial adduction angle of above-knee prostheses was determined by such a definition of the lateral force. Five degrees proved to be the most appropriate angle, as has been generally accepted. The lateral force of floor reaction can be definitely measured by a quantitative analysis of the total impulse during stance phase duration.