The effect of femoral stem size and impaction grafting on proximal stress shielding in the human femur

The hip replacement technique used in revision total hip arthroplasty (THA) is dependent on the amount and quality of cortical bone in the femur. The most common hip replacement techniques include press-fit, cemented, and impaction grafting implants. The effect of femoral stem size and impaction grafting on surface strains of the human femur is the focus of this research. The proximal region of the femur is of great importance due the prevalence of stress shielding, following THA, which can later lead to bone remodeling. A finite element (FE) model was created and compared to intact femur and 15-mm press-fit experimental data. An effective computer model and valid test data contributes to the understanding of stress shielding.; The experimental data show that the strains decreased dramatically from intact femur to the 15-mm implant. The proximal region exhibited the greatest reduction, on average, than any other region of the femur, both experimentally and in the FE model. As the size of the press-fit stem increased, the proximal strains decreased further due to greater contact in the distal end of the stem and increased stiffness within the femoral canal. The results of the tests involving the impaction grafting stems showed that the use of bone graft and a polymer bond distributed the load over the entire volume of the reamed and broached femoral canal, indicating stress shield reduction in the proximal region compared to the press-fit stems.