功能梯度材料胫骨假体的有限元分析

Finite element analysis of functionally graded materials for tibial prosthesis

背景:全膝关节置换后胫骨衬垫的过度磨损,以及关节假体的无菌性松动是导致膝关节假体失效的主要原因。假体与骨骼力学强度差异过大会导致骨上产生应力遮挡,进而诱发假体无菌性松动。目的:利用有限元方法分析植入功能梯度材料(functionally graded materials,FGM)胫骨假体后胫骨假体与胫骨近端松质骨的应力响应。方法:设计了两种不同孔隙率参数的钛合金-羟基磷灰石复合功能梯度材料(命名为FGMⅠ、FGMⅢ)和一种钛合金-理想骨弹性材料复合功能梯度材料(命名为FGMⅡ),其中FGMⅠ的孔隙率参数分别为0.1,1,1,FGMⅡ和FGMⅢ的孔隙率参数分别为0.4,0,1。建立全膝关节置换三维有限元模型,利用仿真软件Abaqus分析FGM与钛合金材料胫骨假体植入后,在伸直位0°及屈曲位30°和60°三种工况下胫骨假体与胫骨松质骨上的应力分布变化。结果与结论:(1)在不同工况下,与钛合金胫骨假体相比,FGM胫骨假体的最大Von Mises应力显著降低,且其松质骨与假体柄端接触部位上的应力明显减小。(2)胫骨松质骨沿不同路径的应力曲线和平均应力表明,在不同工况下,与钛合金胫骨假体相比,使用FGM假体后胫骨近端松质骨上的应力均有提升,其中FGMⅠ提高5.4%-17.3%,FGMⅡ提高1.0%-13.5%,FGMⅢ提高1.6%-15.4%。(3)结果表明,FGM胫骨假体有助于增加胫骨近端松质骨上的应力,减弱胫骨近端的应力遮挡效应,进而可降低胫骨假体无菌性松动发生的概率,延长假体的寿命,且FGMⅠ在3种FGM假体中效果最好。

BACKGROUND:Excessive wear of the tibial insert and aseptic loosening of the prosthesis were the main reasons for the failure of the knee prosthesis after total knee arthroplasty.Owing to the large variation of mechanical strength between prosthesis and bone,it would lead to stress shielding on bone,and then induce aseptic loosening of prosthesis.OBJECTIVE:To analyze the stress response of cancellous bone in proximal tibia after functionally graded materials(FGMs)tibial prosthesis implantation by finite element method.METHODS:Two FGMs with different porosity parameters(FGM I and FGM III)were designed using titanium-hydroxyapatite composite.The other was prepared by titanium-ideal bone repairing material and named FGM II.The porosity parameters of FGM I were 0.1,1 and 1,and the porosity parameters of FGM II and FGM III were 0.4,0 and 1.A three-dimensional finite element model of total knee arthroplasty was established,and the stress distributions of FGM and titanium alloy tibial prostheses were analyzed by Abaqus software under three working conditions of 0°extension,30°and 60°flexion.RESULTS AND CONCLUSION:(1)The maximum Von Mises stresses of FGM tibial prostheses were significantly lower than those of titanium alloy tibial prosthesis,and the stresses at the contact zone between the cancellous bone and the stem end were significantly reduced in FGM tibial prostheses groups.(2)According to the stress curve and average stress of the cancellous bone of the tibia along different paths,the stresses of the cancellous bone of the proximal tibia were increased in FGM tibial prostheses groups compared with titanium alloy tibial prostheses,under different working conditions.Specifically,FGM I was increased by 5.4%-17.3%;FGM II was increased by 1.0%-13.5%;and FGM III was increased by 1.6%-15.4%.(3)The results illustrated that FGM prostheses could increase the stress on the cancellous bone of the proximal tibia and reduce the stress shielding effect of the proximal tibia.Therefore,the risk of aseptic loosening was decreased and the availability of the prosthesis was prolonged.Specifically,FGM I tibial prosthesis was the best among the three kinds of FGM prostheses.