Effect of femoral head shape on mechanical behaviours of artificial hip joint

The human femoral head is not a perfect sphere, but the artificial femoral head is made spherical due to simple manufacturing. The shape may significantly affect the mechanical characteristics of artificial hip joint. This paper is aiming at studying the shape effect of femoral head on mechanical behaviors of artificial hip joint. Three hip joint models with different shapes femoral head were proposed in the finite element analysis software Ansys (version 11.0). Mechanical properties, such as acetabular deformation, were investigated under static and dynamic conditions. In static condition, the acetabular deformation of spherical model is 8.8×10^-5 m, and the deformation for ellipsoidal model and conchoidal model are 3.2×10^-5 m and 3.4×10^-5 m. The acetabular peak stresses are 1.718×10⁷ Pa, 8.87 × 10⁶ Pa and 9.52 × 10⁶ Pa respectively. In the spherical model, peak value occurs in the bottom of the socket, while peak values of the second and third model are obtained at a circle region away from the socket bottom. In dynamic condition, both deformation and peak stress change abruptly. The acetabular deformations are 1.045×10^-3 m, 1.143×10^-3 m and 1.151×10^-3m, the peak stresses are 3.313×10⁸ Pa, 3.260×10⁸ Pa and 3.277×10⁸ Pa. The mean stresses of the second and third model along the sliding direction are lower than the first model. And less deformation is generated near the rim of the acetabulum for the second model.