Biphasic finite element modelling of contact mechanics of hemi-arthroplasty of human hip joint. Part I: Metal on cartilage contact

Biphasic poroelastic finite element (FE) study was performed to investigate the contact mechanics of hemiarthroplasty hip resurfacing using a metallic component, in particular to focus on a parametric study to examine the effects of loading, radial clearance, cartilage thickness and bone quality. Simple axisymmetric FE models of hemi-arthroplasty hip joint were created to simulate the contact between the femoral component (Ti6Al4V alloy) and the acetabular cartilage. Articular cartilage was modelled as biphasic poroelastic material. It was found that the applied load had the greatest effect on the predicted contact pressure and pore pressure distributions among all factors considered in this study. Also it was shown that a reduction in the radial clearance between the articular cartilage of acetabulum and the femoral component had significant effect on the predicted contact pressure and pore pressure distributions along the articulating bearing surface. A decrease in thickness of articular cartilage of acetabulum from its nominal value of 2 mm to 1 mm resulted in 60% increase in the predicted maximum contact pressure and 65% increase in the predicted maximum pore pressure. Stress shielding in the bone tissue was found to occur with the hip resurfacing femoral prosthesis considered in this study. However, the stress shielding was determined to be less than those reported in the literature for metal on metal (MOM) resurfacing and conventional THRs. Bone quality was found to have relatively small effect on the predicted maximum contact pressure and pore pressure.