title: Enhanced wear resistance of orthopaedic bearing due to the cross-linking of poly(MPC) graft chains induced by gamma-ray irradiation.
abstract: We assumed that the extra energy supplied by gamma-ray irradiation produced cross-links in 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer grafted cross-linked polyethylene (CLPE-g-MPC) and investigated its effects on the tribological properties of CLPE-g-MPC. In this study, we found that the gamma-ray irradiation produced cross-links in three kinds of regions of CLPE-g-MPC: poly(MPC) layer, CLPE-MPC interface, and CLPE substrate. The dynamic coefficient of friction of CLPE-g-MPC slightly increased with increasing irradiation doses. After the simulator test, both the nonsterilized and gamma-ray sterilized CLPE-g-MPC cups exhibited lower wear than the untreated CLPE ones. In particular, the gamma-ray sterilized CLPE-g-MPC cups showed extremely low and stable wear. As for the nonsterilized CLPE-g-MPC cups, the weight change varied with each cup. When the CLPE surface is modified by poly(MPC) grafting, the MPC graft polymer leads to a significant reduction in the sliding friction between the surfaces that are grafted because water thin films formed can behave as extremely efficient lubricants. Such a cross-link of poly(MPC) slightly increases the friction of CLPE by gamma-ray irradiation but provides a stable wear resistant layer on the friction surface. The cross-links formed by gamma-ray irradiation would give further longevity to the CLPE-g-MPC cups.
authors.affiliation: Research Division, Japan Medical Materials Corporation, Osaka, Japan. kyomotom@jmmc.jp
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kyomoto
authors.forename: Toru
authors.initials: T
authors.lastname: Moro
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Miyaji
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Konno
authors.forename: Masami
authors.initials: M
authors.lastname: Hashimoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kawaguchi
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Takatori
authors.forename: Kozo
authors.initials: K
authors.lastname: Nakamura
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ishihara
mesh_terms: D001672:Biocompatible Materials; D005720:Gamma Rays; D006622:Hip Prosthesis; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry / Q000528:radiation effects; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000528:radiation effects; D011095:Polyethylenes / Q000737:chemistry; D011108:Polymers / Q000737:chemistry / Q000528:radiation effects*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D001672:Biocompatible Materials; D008689:Methacrylates; D011095:Polyethylenes; D011108:Polymers; C111601:ultra-high molecular weight polyethylene; D010767:Phosphorylcholine; C070638:2-methacryloyloxyethyl phosphorylcholine