Influence of femoral anteversion on proximal femoral loading: measurement and simulation in four patients

Objective. The aim of this study was to determine the loading of the proximal femur during daily activities and to quantify the influence of femoral anteversion. Design. This study combined experimental and analytical approaches to determine the in vivo loading at the hip joint. A numerical musculo-skeletal model was validated against measured in vivo hip contact forces and then used to analyse the influence of anteversion on the loading conditions in the femur. Background. Musculo-skeletal loading of long bones is essential for joint replacement and fracture healing. Although joint contact forces have previously been measured in selected patients, the interaction between femoral anteversion and the associated musculo-skeletal loading environment remains unknown. Methods. The gait of four patients with force measuring hip prostheses was analysed during walking and stair-climbing. Musculo-skeletal loading was determined using individual numerical models by minimising the sum of the muscle forces. Results. Experimentally and numerically determined hip contact forces agreed both qualitatively and quantitatively. Muscle activity resulted in compression of the femur and small shear forces in the meta- and epi-physeal regions. Increasing the anteversion to an angle of 30 degrees increased hip contact forces and bending moments up to 28%. Conclusions. This study has shown that femoral anteversion has a strong influence on the musculo-skeletal loading environment in the proximal femur.