The Individual Modeling And Stress Analysis Of Artificial Femoral Prosthesis Stem

In the course of a femur transplantation, whether it will be succeeded not merely decided by the surgical operation, but mainly affected by the design of the prosthesis, the shape and the material of which determine the stress on the femur. The geometric design of the prosthesis has been researched all the time. The matching between the femur and the prosthesis is an important factor that influences its long curative effect.Because of the absolute individuation characteristic of human body, the standard prosthesis can hardly match to the patient bone, whereas can not ensure the stability of the artificial joint in the long term. Meanwhile, some patients may have congenital malformation in the bone or large area both on the bone and the joint destroyed by pathological change, these bone joints have obvious differences between the normal ones, so a standard prosthesis can' t be selected. In this article, a method of individual prosthesis generating will be put forward which can greatly match to the marrow antrum individually, in which the prosthesis can be designed an made for each patient. To prepare for the first-phase data of this method, the scanned femur data of the patient must be got through CT, then by edge drawing, draw outlines both inside and outside of every layer of the femur. In this important step of data preparation, we edited edge drawing system and 3-D surface reconstruction system, and presented a new angle-based method, which can track and recognize the outlines of the femur, then the petiole of artificial femur would be designed according to the drawn data. In this method, first suppose the femur petiole has already in the marrow antrum, that is, the femur petiole is in the shape of the marrow antrum, then it will be drawn, rotated according to engineering rule. Calculation, especially cutting calculation should be carried out at every certain drawing distance, repeat it till the whole petiole was drawn out. Finally, add correspondingly characteristic head and neck of the femur to make the model with Solidworks software.In order to prove that the model of individual artificial femoral prosthesis is more optimal than the normal series, two models of normal prosthesis were built, one is of cement, the other biology. The three models were put on the Solidworks software platform, simulating comparative mechanical experiment was carried out both on the load of standing still on double feet and single foot, investigate the two important mechanical characters of stress distribute on the prosthesis and femur as well as prosthesis substitution effect on surface stress. The result was: on the load of standing still on double feet or single foot, stress on the former prosthesis was much less than that of the normal biology and the cement models, moreover, the stress distribution on the former was more equal. Correspondingly, the stress on the femur was much less than that of the others, also the stress distribution was even more equal. All of these proved that the stress on the former could transmit fast and reach the end of the femur directly. The stress on the femur transferred through prosthesis would be correspondingly minimized, and distributed much equally. So, it's more optimal than the normal ones on biomechanical performance. As to the effect of the substitution of the prosthesis on the surface stress, normally there are two kinds of stress on the bone surface that is the normal stress and the shearing stress. More surface stress will lead to less tight combination of the prosthesis and the bone, as well as the relative movement between them, that will cause the prosthesis loose. From this experiment we also can draw the conclusion that on the load of standing still on double feet or single foot, stress on the model of individual artificial femoral prosthesis is much less than that of the normal biology and the cement models, especially the shearing stress of which is even less than the latter two models. All of above illustrates that the both the normal stress and the shearing stress...