Shock absorption property of the knees with and without total knee joint replacement

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Among many factors, which induce implant loosening, stress concentration in the bone prosthesis interlace is thought to play an important role. We thought stiff and rigid mechanical properties of the total joint prosthesis would cause less shock absorption and concentration of abnormal stress at bone prosthesis interface. The purpose of this study was to analyze propagation of shock wave and shock absorption properties of the knee joint with and without total joint prosthesis. Impact loading was applied to the lower limb and the effect of different types of tibial prostheses on stress distribution was analysed. The experiment was first carried out by using fresh human cadaver knees with a specially designed jig, which allowed measuring the transmitted impact load. It was found that the load transmitted was significantly higher in the knees with prostheses compared with the intact knees. When load transmission and stress distribution was investigated by dynamic finite element analysis m … More odel, the knees with total knee prostheses showed significantly different pattern compared to the physiologic knees. The impact load was transmitted to the central stem of the tibial prosthesis immediately after loading and thereafter concentration of the stress was noted in the cortical bone of the tibia (245 % of the stress compared to physiologic condition). In this dynamic finite element analysis model, stress distribution and micromotion at the interface between the bone and prosthesis could be changed with modification of the shape of the tibial prosthesis. It was found that the tibial prosthesis with the keels tended to show better stress distribution and lower the maximum stress. It was also noted that the tibial prosthesis with a central stem prevented excessive micromotion. We believe that analysis with dynamic impact load would better simulate load transmission behavior of the knee joint and the implant design, which reduces stress, and micromotion under this condition could possibly provide better survivorship after implantation. Less