Influence of cartilage layer modelling on the FE-simulation of femoral head stress

The present study reports on the finite element analysis (FEB) of the femor al head in a process of preparation for a program for the realistic simulat ion of correctional osteotomies of the proximal femur. While the material p roperties have been studied extensively, only few publications consider the influence of the cartilage layer geometry on FE simulation of the hip join t. Various models of the femoral head with and without the cartilage layer are generated and analysed. On looking at the maximum surface stresses, we found a strong influence of the cartilage layer and the subchondral osseous layer on the magnitude of the von Mises equivalent stress. The model with an anatomically realistic cartilage layer and compact bone shows stresses o f between 4 and 5.5 MPa, depending on the position of the joint, while the model with a concentric cartilage layer has a maximum von Mises stress of 0 .8 MPa. Only on simulation of a "realistic" cartilage layer, with a maximum thickness at the "pole" and minimum thickness at the "equator" do the chan ges in stress distribution - determined by changes in the position of the f emoral head - become visible. Owing to major artefacts and the inability to create a realistic cartilage layer, voxel-based models of the femur are no t suitable for the simulation of the femoral head surface.