Hedia H S
Design Department, Faculty of Engineering, Mansoura University, Egypt.
Biomed Mater Eng. 2001;11(2):79-88.
This paper describes a method of parametric optimisation to determine the optimal stiffness characteristics of cement, metal backing and UHMWPE (Ultra High Molecular Weight Polyethylene) materials, which minimises the probability of fatigue fracture of cement at all interfaces with the metal backing and the bone, while limiting the amount of bone resorbed. The parameters describing the elastic moduli of cement, metal backing and UHMWPE were considered as design variables. The method was applied to an axisymmetric finite element model of acetabular cup in combination with an optimisation procedure using the ANSYS program. Young's moduli of about 0.63, 207 and 0.72 GPa are optimal materials for cement, metal backing (MB) and UHMWPE, respectively. These characteristics decreased fatigue notch factor Kf in cement by 8.2 and 10.6% and also decreased the maximum von Mises stress in cement by 21 and 27% at cement/bone and cement/metal backing interfaces, respectively. The optimal design reduces the probability of fatigue fracture of cement at all interfaces with the bone and the metal backing while limiting the amount of bone resorbed as a result of increasing von Mises stress and Kf in the central bone of the acetabulum by 34 and 30.6%, respectively.
本文描述了一种参数优化方法，用于确定水泥、金属背衬和超高分子量聚乙烯（UHMWPE）材料的最佳刚度特性，该方法可将水泥在与金属背衬和骨骼的所有界面处发生疲劳断裂的概率降至最低，同时限制骨吸收量。将描述水泥、金属背衬和UHMWPE弹性模量的参数视为设计变量。该方法与使用ANSYS程序的优化过程相结合，应用于髋臼杯的轴对称有限元模型。对于水泥、金属背衬（MB）和UHMWPE，约0.63、207和0.72 GPa的杨氏模量分别是最佳材料。这些特性使水泥中的疲劳缺口因子Kf分别降低了8.2%和10.6%，并且在水泥/骨骼和水泥/金属背衬界面处，水泥中的最大冯·米塞斯应力分别降低了21%和27%。优化设计降低了水泥在与骨骼和金属背衬的所有界面处发生疲劳断裂的概率，同时由于髋臼中心骨中的冯·米塞斯应力和Kf分别增加了34%和30.6%，限制了骨吸收量。
