Material optimization of a cemented tibia tray using functionally graded material

Joint replacement surgeries are doubtlessly the gift of science and technology for human welfare. In the cemented knee replacement joint, the stiffer implant carries the majority of the load, which is actually carried by the bone itself before implantation. The resulting implant induced stress-shielding and subsequent bone remodeling causes bone resorption at the proximal bone under the tibia tray. The aim of this study is to optimize the material of the cemented tibia tray using functionally graded material FGM. The target is to find the optimal material and the optimal gradation direction for the cemented tibia tray. The results showed that the optimal vertical FGM changed from titanium at the lower tibia stem to bioglass at the upper layers of the tibia tray. The vertical FGM reduced the stress shielding by 56 and 80 % in cancellous epiphyseal and diaphyseal bone, respectively, compared to cemented titanium tibia tray. However, the optimal horizontal FGM changes from titanium at the stem core to bioglass at the rim of tibia tray layers. This horizontal gradation reduced the stress shielding in cancellous epiphyseal bone by 62 %. However, the stress shielding in cancellous diaphyseal bone did not change compared to cemented titanium tibia tray.