Polyethylene

As the contact of the articular surface of knee joint is convex, soft and tough material is required for artificial knee joint. Polyethylene with vitamin E for artificial knee joints was developed in Japan to improve the formability of UHMWPE and the fusion of powders to prevent oxidative fatigue destruction at the raw powder interface. The results of the mononuclear phagocytosis assay showed that human peripheral blood mononuclear cells contact with polyethylene mixed with vitamin E produced almost no TNF-alfa, interleukin(IL)-1beta, IL-6, and IL-8 14). Although the mechanism underlying this effect has not yet been clarified, if the generation of radical in polyethylene and the continuous oxidation of polyethylene by the radicals are suppressed, a long-term osteolysis inhibitory effect can be expected in vivo. No direct evidence exists regarding whether the inclusion of vitamin E suppresses osteolysis in clinic. As for next-generation knee prosthesis, high durability to cope with intense dynamic movements, such as hard work and sports, is required.