Toward verified and validated FE simulations of a femur with a cemented hip prosthesis

Background: Verified and validated CT-based high-order finite element (FE) methods were developed that predict accurately the mechanical response of patient-specific intact femurs. Here we extend these capabilities to human femurs undergoing a total hip replacement using cemented prostheses. Methods: A fresh-frozen human femur was CT-scanned and thereafter in vitro loaded in a stance position until fracture at the neck. The head and neck were removed and the femur was implanted with a cemented prosthesis. The fixed femur was CT-scanned and loaded through the prosthesis so that strains and displacements were measured. High-order FE models based on the CT scans, mimicking the experiments, were constructed to check the simulations prediction capabilities. Results: The FE models were verified and results were compared to the experimental observations. The correlation between the experimental and FE strains and displacements were (R² = 0.97, EXP = 0.96FE + 0.02) for the intact femur and (R² = 0.90, EXP = 0.946FE + 0.0012) for the implanted femur. This is considered a good agreement considering the uncertainties encountered by the heavy distortion embedded in the CT scan of the metallic prosthesis. Discussion: The patient-specific FE model of the fresh-frozen femur with the cemented metallic prosthesis showed a good correlation to experimental observations, both when considering surface strains, displacements and strains on the prosthesis. The relatively short timescale to generate and analyze such femurs (about 6 h) make these analyses a very attractive tool to be used in clinical practice for optimization prostheses (dimensions, location and configuration), and allow to quantify the stress shielding.