The hip-joint resultant force in healthy male and female population: a comparative study

The geometrical parameters of the pelvis and the femur which influence the hip-joint reaction force were obtained automatically for 21 male and 79 female healthy human subjects from standard AP radiographs, by using a computeraided system. To calculate the hip-joint reaction force a three-dimensional mathematical model of the hip in one-legged stance was used. In order to prepare the data as input to the mathematical model of the hip a nonhomogeneous scaling method based on a reference model of the hip musculature by Dostal and Andrews was applied. Our results show that the magnitude of the hip-joint reaction force and its inclination angle are significantly greater for females than for males. Since females have in addition significantly smaller femoral head radius than males, it may be concluded that the stress in the hip-joint articular surface is higher in the female population relative to the male population. Because the increased stress in the hip-joint articular surface is unfavourable regarding the arthrosis development, the presented results could partially explain the fact that females have greater incidence of arthrosis in the hip-joint than males.This is related not only to femoral, but also to pelvic geometry.