Selection Methodology of Femoral Stems According to the Cross Section and the Maximum Stresses

The maximum stresses on a femoral stem must be known for selecting the right size and shape of the shaft cross-sectional area for reducing the stress shielding effect generated after the total hip arthroplasty (THA) surgical procedure. The methodology proposed in this study provides the tools to the designers of femoral stems and orthopedic surgeons to select the adequate femoral stem cross section, decreasing the stiffness of the stem, thus reducing the stress shielding effect in the patient bones. The first contribution is the theoretical development of the maximum static stress calculation for 12 different femoral stem models with the beam theory, followed by the comparison with the static finite element analysis (FEA) simulations and finally the experimental corroboration of one femoral stem model measuring the strain with linear strain gages and transform it to stresses, the three different approaches provide comparable results, with a maximum average error of less than 8.5%. The second contribution is the formulation of a new selection methodology based on maximum stresses in the femoral stem and the cross section area for decreasing the stress shielding effect, optimizing the area needed for withstand the loads and decreasing the overall stiffens of the stem.