Design of low wear artificial hip joint considering 3D physiological loading and motion

Wear of the bearing surfaces of an artificial hip joint (AHJ) is one of the major causes to the premature failure of the prosthesis. Any design aiming at the surface wear reduction is of significance and the first primary understanding that should be achieved is to clarify the variation of the contact trajectories and the variation of the contact stresses and areas between the femoral head and acetabular cup of an AHJ while a person is walking or running. The purpose of present work is to develop an effective mechanism model to investigate the wear at the bearing surfaces of a hip joint prosthesis under the three-dimensional motion and loading conditions under patient's walking activities. The femoral heads and acetabular cups of various dimensions were constructed by the finite element method to explore the effect of design parameters on the contact wear of their bearing surfaces. For an accurate prediction, the trajectory of the contact area in the bearing surfaces was analyzed, showing the variations in contact radius and contact stress. It was found that the sliding trajectory on the acetabular cup mainly concentrated in some specific regions. After 10 cycles of gait walking, an AHJ with thicker cup thickness or smaller femoral head radius would have less volumetric wear, whereas that with thinner cup thickness or larger femoral head radius would have less linear wear.