The effect of anatomical positional relationships on kinetic parameters after total hip replacement.

The purpose of this study was to evaluate the significance of positional relationships of the components on gait after total hip replacement (THR). Gait was analysed using multicomponent force platforms integrated into a treadmill, in conjunction with an optoelectric measuring system. 26 patients, after undergoing total hip replacement, were classified according to the vertical and horizontal positions of the centre of rotation, the vertical position of the femur and the functional leg length, and compared with a control group. Deterioration in parameters of gait was observed following cranialisation of the centre of rotation or of the femur, whereas neither medial movement of the centre of rotation nor leg lengthening by up to 1 cm had any effect. This study emphasises the importance of considering, at the time of preoperative planning, the effect of the position of the prosthesis on the functional parameters of gait.