The Three-dimensional Reconstruction Of Femur And Finite-Element Analysis Of Hip Joint Replacement

The finite-element methods applied in biomedical engineering have brought revolution to medical techniques. However, more serious inconveniences to patients caused by the loss of hip joint function are brought by pathologic change and accident etc. In the course of a femur transplantation, whether it will be succeeded is not only decided by the surgical operation, but mainly affected by the design of prosthesis, the shape and material of which determine the stress on the femur. The custom-built artificial femur prosthesis achieves the best match of the prosthesis with medullar cavity in total hip joint replacement; so that it can be more adaptable to biomechanics environment in body and have the advantages of getting rid of femoral normal stress destruction, reducing stress shielding and prolonging prosthesis longevity. In this topic, according to the diversity of femoral geometric shape and the complexity of femoral structural material, the three-dimensional reconstruction of femoral research methods is proposed; the static analysis, modal analysis, gait analysis and some parameters of prosthetic hip replacement about femur are conducted based on three-dimensional reconstruction of the femur, which would be helpful for design and fabrication of individualized hip prosthesis.Mimics,Geomagic and SolidWorks software enables that the CT data transfer precisely between CT and PC, and the femur three-dimensional reconstruction, the constructed models is highly precise. Moreover, its solid model is also fabricated by Rapid Prototype (RP).The material assignment is applied by MIMICS based on gray scale; the finite element model material of femur is realized in unevenness and anisotropism. The data transmission interface is set up between Mimics and Ansys, the intact femur was used in some kinds of FEA, for example, static analysis, modal analysis and dynamic analysis. The main conclusion is: the property of femur is linear; the matching inherent frequency between femur and prosthesis is provided by the pre-seven inherent frequencies; the range of femur stress always mainly in the middle and lower 1/3.Combining with the femoral anatomical structural characteristics of the spinal cord cavity, CAD software SolidWorks is used to design prosthesis, a method of individual prosthesis generating which can greatly match to the marrow antrum individually will be put forward. The femur-prosthesis model is assembled in the Mimics and Ansys to put up contact coupling analysis. Three different materials and three different stem-lengths prosthesis were simulated and the stress of prosthesis and femur intact and implanted was analyzed, The results indicated that the stress pattern of femur implanted was similar to the one of intact femur. Compared to proximal femur the stress shielding at middle femur was reduced. As the rigidity of prosthesis decreased, the stress of prosthesis decreased, but the stress of proximal femur increased obviously. The results also showed that the increased length of the stem brought the increased stress of femur slightly, but had little effect on the stress ofprosthesis.The research can not only provide biomechanics parameter exactly for new style man-made joint design and clinical application, but also offer some helpful bases for the design, replacement and life of artificial hip joint.