Tissakht M, Ahmed A M, Chan K C
Department of Mechanical Engineering, McGill University, Montreal, Quebec, Canada.
J Orthop Res. 1996 Sep;14(5):778-85. doi: 10.1002/jor.1100140515.
This study sought to determine the similarities between features of calculated stress-shielding and observed bone loss in the distal femur after total knee replacement. Stress-shielding was determined by comparing the magnitudes and distributions of strain energy density, calculated using three-dimensional finite element models of the intact bone, the bone after total knee replacement with bonding assumed at all prosthesis-bone interfaces, and the bone after total knee replacement with bonding assumed only at the distal interface. The loading condition simulated static lifting with the knee flexed at 45 degrees, producing tibiofemoral and patellofemoral joint reactions of 900 and 450 N, respectively. The maximum magnitudes of strain energy density calculated using the total knee replacement models were less than 15% of the corresponding magnitudes from the intact bone model. The greatest difference was found to occur at the anterior distal corner of the femur, suggesting this location as the one most vulnerable to stress-shielding. Clinically observed bone loss after total knee replacement frequently occurs at this location. At the anterior distal corner, the calculated magnitudes for the two total knee replacement models were similar, suggesting that stress-shielding at this location was not reduced by limiting fixation only to the distal interface. Although the study corresponded to one loading condition and one geometry of the total knee replacement femoral component with the inherent limitations of model calculations, the results suggest a possible scenario for stress-shielding.
本研究旨在确定全膝关节置换术后股骨远端计算得出的应力遮挡特征与观察到的骨质流失之间的相似性。通过比较应变能密度的大小和分布来确定应力遮挡，应变能密度使用完整骨骼的三维有限元模型、假定所有假体 - 骨界面均有骨结合的全膝关节置换术后骨骼模型以及仅假定远端界面有骨结合的全膝关节置换术后骨骼模型进行计算。加载条件模拟膝关节屈曲45度时的静态提举，分别产生900 N和450 N的胫股关节和髌股关节反应。使用全膝关节置换模型计算得出的应变能密度的最大大小小于完整骨骼模型相应大小的15%。发现最大差异出现在股骨远端前角，表明该位置是最易受应力遮挡影响的部位。全膝关节置换术后临床观察到的骨质流失经常发生在该位置。在远端前角，两个全膝关节置换模型的计算大小相似，表明仅将固定限制在远端界面并不会减少该位置的应力遮挡。尽管该研究对应于一种加载条件和全膝关节置换股骨部件的一种几何形状，存在模型计算固有的局限性，但结果表明了一种可能的应力遮挡情况。
