Liau Jiann Jong, Cheng Cheng Kung, Huang Chun Hsiung, Lo Wai Hee
Orthopaedic Biomechanics Laboratory, Institute of Biomedical Engineering, National Yang Ming University, No. 155, Sec. 2, Li-Nung St., Shih-Pai, 11221, ROC, Taipei, Taiwan.
Clin Biomech (Bristol). 2002 Feb;17(2):140-6. doi: 10.1016/s0268-0033(01)00109-7.
To investigate the effects of malalignment on stresses in tibial polyethylene component of total knee prostheses.
A three-dimensional finite element analysis was used to calculate the contact stress and von Mises stress in the tibial polyethylene component subjected to a compressive load, and the malalignment situations were simulated.
Many biomechanical studies to investigate the stresses in tibial polyethylene component were assumed at the ideal contact alignment. The effect of malalignment on stresses in tibial polyethylene component was not investigated extensively.
Three-dimensional finite element models of the tibiofemoral joint of knee prostheses for three different designs were constructed. Three malalignment conditions including the medial translation (0.25, 0.5 and 1.0 mm), internal rotation (1 degree, 3 degree and 5 degree), and varus tilt (1 degree, 3 degree and 5 degree) of the femoral component relative to the tibial component were simulated. A compression load of 3000 N was applied to the tibiofemoral joint at 0 degree of flexion. The maximum contact stress and von Mises stress in the tibial component were compared to investigate the effects of malalignment.
In comparing with the neutral position, the greatest increase of maximum contact stress were 67.6%, 14.3% and 145.9% and the greatest increase of maximum von Mises stress were 92.5%, 22.7% and 120.6% in maltranslation, internal rotation and varus tilt simulations, respectively.
The greatest increase of contact stress and von Mises stress was occurred in the high conformity flat-on-flat design of knee prosthesis under the severest malalignment condition. The high conformity curve-on-curve design of knee prosthesis has the minimal risk of polyethylene wear under the malalignment conditions.
This study revealed the importance of malalignment effect on stresses in tibial polyethylene component. Polyethylene wear in surface replacement total knees will be minimal when a high conformity curve-on-curve knee design is used and the rotational line between the femoral and tibial components has the least effect on polyethylene wear but varus/valgus malalignment, even with the best designed prosthesis will still accelerate wear.
研究对线不良对全膝关节假体胫骨聚乙烯部件应力的影响。
采用三维有限元分析方法，计算在压缩载荷作用下胫骨聚乙烯部件的接触应力和冯·米塞斯应力，并模拟对线不良情况。
许多研究胫骨聚乙烯部件应力的生物力学研究都是在理想接触对线的假设下进行的。对线不良对胫骨聚乙烯部件应力的影响尚未得到广泛研究。
构建三种不同设计的膝关节假体胫股关节三维有限元模型。模拟了三种对线不良情况，包括股骨部件相对于胫骨部件的内侧平移（0.25、0.5和1.0毫米）、内旋（1度、3度和5度）以及内翻倾斜（1度、3度和5度）。在屈膝0度时，对胫股关节施加3000牛的压缩载荷。比较胫骨部件中的最大接触应力和冯·米塞斯应力，以研究对线不良的影响。
与中立位置相比，在平移不良、内旋和内翻倾斜模拟中，最大接触应力的最大增幅分别为67.6%、14.3%和145.9%，最大冯·米塞斯应力的最大增幅分别为92.
5%、22.7%和120.6%。
在最严重的对线不良情况下，膝关节假体的高顺应性平面-平面设计中接触应力和冯·米塞斯应力的增幅最大。在对线不良情况下，膝关节假体的高顺应性曲面-曲面设计聚乙烯磨损风险最小。
本研究揭示了对线不良对胫骨聚乙烯部件应力影响的重要性。当使用高顺应性曲面-曲面膝关节设计时，表面置换全膝关节中的聚乙烯磨损将最小，并且股骨和胫骨部件之间的旋转对线对聚乙烯磨损的影响最小，但内翻/外翻对线不良，即使是设计最佳的假体仍会加速磨损。
