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

在导致种植体松动的诸多因素中，假体间隙的应力集中被认为起着重要的作用。我们认为，全关节假体僵硬的力学性能会导致假体界面处的减震和异常应力集中较少。本研究的目的是分析有无全关节假体时膝关节的冲击波传播和减震特性。对小腿施加冲击载荷，分析不同类型的胫骨假体对应力分布的影响。这项实验首先是使用新鲜的人身体膝盖和专门设计的夹具进行的，这种夹具可以测量传递的冲击载荷。结果发现，假体膝关节所传递的载荷明显高于完整膝关节。用…进行动力有限元分析载荷传递和应力分布更典型的是，全膝关节假体与生理性膝关节相比，表现出明显不同的形态。加载后立即将冲击载荷传递到胫骨假体的中央干，此后应力集中在胫骨皮质骨(与生理状态相比，应力的245%)。在该动态有限元分析模型中，随着假体形状的改变，骨与假体界面处的应力分布和微运动都会发生变化。研究发现，带龙骨的胫骨假体具有更好的应力分布和更低的最大应力。人们还注意到，带有中央柄的胫骨假体防止了过度的微运动。我们认为，动态冲击载荷分析可以更好地模拟膝关节的载荷传递行为和植入物的设计，从而降低应力，在此条件下的微运动可能会提供更好的植入物存活率。较少

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