Personalized finite element model of a cementless femoral stem. A preliminary study
Valéry Barbour,* Aurelien Courvoisier, Michel Thourot, David Mitton and Wafa Skalli
Laboratoire de Biomécanique, Arts et Métiers ParisTech, 151 Boulevard de l'hôpital, 75013 Paris, France
The purpose of the present work was to develop a personalized finite element model of a cementless stem to assess the immediate post-operative load transfer at the implant–bone interface. We developed a new technique using force-sensing resistors to gather in vitro pressure values at this interface for a cementless implant. The stem was instrumented with six calibrated sensors bonded on each facet and then implanted in a cadaver femur. A destructive compressive test was performed and pressure values were recorded. The finite element models of the stem and the femur were meshed separately (Ansys) from the 3D model for the stem and from a computer tomography (CT) scan for the femur. The stem material properties were assumed to be those of an isotropic titanium alloy (Young’s modulus = 110 000 MPa and Poisson’s ratio = 0.3). A CT-based average elastic modulus of 10 239 MPa was assigned to the femur. Boundary conditions were applied according to the experiments and implant–bone contact zones were obtained from EOS stereoradiographs (Biospace Med). Successive 500 N load steps were simulated until the experimental failure load was reached. The map of pressures obtained by the model corresponded to the local experimental variation. This model can facilitate the optimization of new femoral cementless implants developed to implement the ideal design supporting osteointegration and load transfer.
Keywords: force sensing resistors, hip, load transfer, pressure measurements, stem