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 (R(2)=0.97, EXP=0.96FE+0.02) for the intact femur and (R(2)=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 6h) 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.