In vitro modeling of the loading of a hip joint endoprosthesis from С/С composite with damaged areas

The influence of the biological process of osteointegration on the change of elastic modules of the material of the leg of the hip joint (c/c composite) in areas with damage to pyrocarbon crystallites has been studied. Damage occurs as a result of extreme loads performed by a person, which leads to a decrease in the bearing capacity of the endoprosthesis leg. As a result of damage, the pyrocarbon matrix becomes similar to a loose granular medium, which significantly reduces the elastic properties of the material as a whole. A positive change in the elastic modules of the endoprosthesis leg material during osseointegration can lead to blocking the spread of damaged areas and an increase in the bearing capacity of the endoprosthesis. The prediction of elastic modules in the damaged areas of the endoprosthesis is performed in two stages. At the first stage, the elastic properties of the new matrix in the damaged areas are calculated, which is a combination of osteoblasts and a pyrocarbon matrix of a c/c composite. At the next stage, the effective properties of a unidirectional c/c composite with a modified matrix are calculated. When predicting elastic modules, the direct homogenization method implemented in the Ansys Material Designer module is used. The prediction of the effective properties of a three-dimensional reinforced c/c composite, in the pores of which osteoblasts are embedded, is performed according to the Tarnopolsky model. When modeling loading, spatial models of human bones are used, obtained using computed tomography and converted into solid-state models. The magnitude of the load on the biomechanical system is determined by the bearing capacity of the endoprosthesis leg in case of damage in four areas without taking into account the introduction of osteoblasts. The study presents the results of calculations of stress and strain fields for the hip joint endoprosthesis structure and presents a diagram of the deformation of the endoprosthesis leg in load- displacement coordinates, showing the altered bearing capacity of the endoprosthesis. The numerical results clearly demonstrate the influence of the biological process of osteointegration on the change in the bearing capacity of the endoprosthesis and elastic properties in the damaged areas of the material.