Biomechanical Optimization of Elastic Modulus Distribution in Porous Femoral Stem for Artificial Hip Joints
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Long-term loosening is the major cause of failure of arthroplasty. One of the major causes is stress shielding, initiated by the large stiffness difference between prosthesis and bone tissue. Therefore, prosthesis with reduced stiffness properties to match those of the bone tissue may be able to minimize such a problem. Design with porous structure is believed to reduce the stiffness of the prosthesis, however at the cost of decreased strength. In this study, a patient-specific bone-implant finite element model was developed for contact mechanics study of hip joint, and algorithms were developed to adjust the elastic modulus of elements in certain regions of the femoral stem, until optimal properties were achieved according to the pre-defined criterions of the strength and stability of the system. The global safety factor of the optimized femoral stem was 11.3, and 26.4% of elements were designed as solid. The bone volume with density loss was reduced by 40% compared to the solid stem. The methodology developed in this study provides a universal method to design a patient-specific prosthesis with a gradient modulus distribution for the purposes of minimizing the stress shielding effect and extending the lifespan of the implant.
Keywordsfinite element analysis elastic modulus distribution porous prosthesis femoral stem stress shielding
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The work was supported by the funding from the program of the National Nature Science Foundation of China (Grant Nos. 51205303 and 51323007), the program of Scientific and Technological Innovation in Shaanxi Province (Grant No. 2014KTZB01-02), the Fundamental Research Funds for the Central Universities, and Research Fund for the Doctoral Program (RFDP) of Higher Education of China.
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