A calculation of the forces acting on the human acetabulum during walking. Based On in vivo force measurements, kinematic analysis and morphometry.

Information about the loading of the human acetabulum during walking is necessary for a functional understanding of the morphology of the pelvic girdle and the hip joint as well as for the optimization of endoprosthetic therapy in osteoarthritis. For this purpose, experimental data of the forces acting on the femur in walking taken from the literature [Bergmann et al.: J. Biomech. 1993;26: 969-990] were combined with our own kinematic and morphometric data, to transform the force vectors from the femoral into a pelvic and an acetabular frame. During the walking cycle, the resultant force vector takes a rather constant course relative to the pelvis and its orientation seems to be highly regulated to act within a small range of angles. Only small deviations occur from the angles against the vertical which the resultant peak force forms in the frontal plane (F = 11 degrees, medially orientated) and in the sagittal plane (S = 5 degrees, ventrally orientated). The experimental results form the basis for a model of the incongruous hip joint as an elastic joint, the femoral head being centered between compliant elements.