Stress shielding reduction via graded porosity of a femoral stem implant

Abstract After hip replacement surgery there will be a clear distinction between the stiffness of the metallic implant and the more supple femur bone which will cause stress shielding and bone resorption. In order to treat this phenomenon, the stiffness of the femoral stem implant must be reduced. The effect of using porous and non-porous implants of steel, titanium and FGM will be studied in this research. The assembly of the femur bone and the implant was modeled by means of the 3D finite element method. It will be noticeable from this analysis that for all stem materials using porous implant materials lead to an increase in stress in cortical and cancellous bone as compared to non-porous implant materials which lead to reduced stress shielding and bone resorption. Gradually increasing the porosity of a steel stem from the distal part of the stem to the proximal part increased maximum von Mises stress at the proximal medial cortical bone by 29 % when compared to the non-porous steel stem. By contrast, von Mises stress at the proximal medial cortical bone increased by about 21 % for porous titanium and porous FGM as compared to non-porous titanium and FGM stem implants.