title: Oxidation and wear of 100-Mrad cross-linked polyethylene shelf-aged for 30 years.
abstract: Some previous studies suggest that aging influences wear and oxidatively degraded nonsterilized ultra-high-molecular-weight polyethylene (UHMWPE) exhibits decreased wear resistance. We therefore asked whether shelf-aging storage conditions influenced degradation and wear resistance of gamma-irradiated UHMWPE. We examined oxidation and wear of 100-Mrad gamma-irradiated UHMWPE (100-Mrad polyethylene) cups shelf-aged for 30 years without (n=2) or with (n=2) packages. The oxidation index of the unpackaged 100-Mrad polyethylene surface (4) was higher than that of the packaged one (2.7). The packaged 100-Mrad polyethylene cup exhibited a high wear resistance with a steady wear rate of 0.5 mg/10(6) cycles. In contrast, the unpackaged 100-Mrad polyethylene exhibited an extremely high initial wear rate of 187.9 mg/10(6) cycles over the first 0.25 x 10(6) cycles with a subsequently reduced wear rate of 5 mg/10(6) cycles after 5 x 10(6) cycles. Packaging over long periods inhibits surface oxidation and maintains the wear resistance of gamma-irradiated UHMWPE cups.
authors.affiliation: H. Oonishi Memorial Joint Replacement Institute, Tominaga Hospital, Osaka, Japan.
authors.forename: Hironobu
authors.initials: H
authors.lastname: Oonishi
authors.forename: Sok Chol
authors.initials: SC
authors.lastname: Kim
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Oonishi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kyomoto
authors.forename: Shingo
authors.initials: S
authors.lastname: Masuda
mesh_terms: D005609:Free Radicals; D005720:Gamma Rays; D006622:Hip Prosthesis / Q000592:standards*; D008422:Materials Testing; D010084:Oxidation-Reduction; D020959:Polyethylene / Q000737:chemistry* / Q000528:radiation effects; D019064:Product Packaging; D013242:Sterilization
chemical_list: D005609:Free Radicals; D020959:Polyethylene