RESUMO
To solve the problem of aseptic loosening of hip joint prosthesis after THR (total hip replacement) and to meet the requirement of individual endoprosthesis for rapid automatic design and manufacture, a new method is presented. According to the anatomical shape of the patient's femoral marrow cavity and the replacement requirement, the hip joint prosthesis is designed via the combination of medical CT technique, computer aided design and finite element analysis. During analysis of the endoprosthesis, the 3-D finite element model of the femur is structured by finite element software ANSYS, the near true femoral material parameters are gained, the quantitative description of femoral material's anisotropy and inhomogeneity is realized by self-developed specific software in the 3-D finite element model of femur. Contact analyses of the customized hip endoprosthesis--femur system are simulated by ANSYS, stress, strain and their distribution are analyzed and contrasted before and after-operation under the action of physiological load in the system. It is feasible to checkout the rationality of the design by comparing the stress distribution in the femur with the situation before replacement, the extent of stress-shielding caused by the replacement is determined quantificationally. The results reveal that the method is more reasonable and reliable and can provide basic means for optimizing the design of custom-made hip prostheses and for evaluating the long-term stability of endoprosthesis after operation.