Abstract
The present study was undertaken to examine the effects of reduced hip extension while walking on displacement of the center of gravity in patients soon after total hip arthroplasty (THA). The subjects of this study were 9 women who had undergone unilateral THA 4 weeks previously and 11 healthy women. Using a force plate and a three-dimensional motion analyzer we measured: 1) gait velocity, 2) flexion-extension motion of hip and knee joints, 3) displacement of the center of gravity, 4) positive work volume during each double-supporting phase, and 5) the total internal work done per unit mass and distance walked. In the THA group, the hip extension decreased and flexion-extension motion of the knee was absent during the stance phase. When the amount of positive work during each double-supporting phase was analyzed for the THA group, the amount of positive work after the heel contact phase was significantly greater on the operated side than on the intact side. The data obtained concerning the total internal work done per unit mass and distance walked indicated a lack of efficient displacement of the center of gravity. These results suggest that the decrease in hip extension while walking after THA can reduce the upward driving force in pushing off and inhibit knee motion control during the stance phase on the side where surgery was performed, suppressing smooth displacement of the center of gravity.
