Axisymmetric Finite Element Analysis of a Hip Replacement with an Elastomeric Head: the Eeffects of Layer Thickness

Finite element analysis of compliant layered artificial hip joints has been used to study the mechanical response of four different layer thicknesses from 0.5 to 3 mm.The results have been compared with a classical asymptotic model in terms of maximum contact pressure and contact width, and of maximum shear stress at the layer-backing interface and its location.The surface deformations and load capacities have also been compared.The best thickness was found to be 2 mm; though a marginal reduction in stresses would be found in the 3 mm layer, the penetrations would be greater and these might have implications for the fatigue life of the material.A formula for the thickness of the fluid film has been derived on the basis of the inverse hydrodynamic theory and the results show good correlation with existing theories.