title: Quantifying the effect of resin type and sterilization method on the degradation of ultrahigh molecular weight polyethylene after 4 years of real-time shelf aging.
abstract: Alternative sterilization methods including ethylene oxide, gas plasma, and gamma-radiation in an inert environment were implemented in the late 1990s, to limit oxidative degradation of ultrahigh molecular weight polyethylene (PE). There was also a simultaneous transition to PE resins that did not contain calcium stearate. Shelf storage duration of PE inserts following gamma-irradiation in air has been correlated to poor clinical performance and increased wear. This study aimed to determine how sterilization method and resin type influenced degradation of PE after 4 years of real-time shelf aging. It was hypothesized that gamma-irradiation and stearate containing resins would incur significantly more degradation than nonradiated, stearate-free resins. Gamma-irradiated PE samples in air and nitrogen had a significantly increased density and oxidation index, compared to nonirradiated PE after 4 years of shelf aging. Alternative sterilization methods such as ethylene oxide and gas plasma appeared to have significantly less oxidation regardless of PE resin type. A partial correlation demonstrated that density and oxidation index were not correlated (r(2) = 0.079) when examining the influence of sterilization method. The data supported that after 4 years of real-time shelf aging, the type of sterilization method had a larger influence on PE degradation than resin type.
authors.affiliation: Bone & Joint Research Lab (151F), Salt Lake City Veterans Affairs Health Care System, and Department of Bioengineering, University of Utah, USA.
authors.forename: Bettina M
authors.initials: BM
authors.lastname: Willie
authors.forename: Shadi
authors.initials: S
authors.lastname: Ashrafi
authors.forename: Sanjin
authors.initials: S
authors.lastname: Alajbegovic
authors.forename: Trever
authors.initials: T
authors.lastname: Burnett
authors.forename: Roy D
authors.initials: RD
authors.lastname: Bloebaum
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry* / Q000378:metabolism*; D019544:Equipment Failure Analysis; D005720:Gamma Rays; D006801:Humans; D008422:Materials Testing; D010084:Oxidation-Reduction; D011095:Polyethylenes / Q000737:chemistry* / Q000378:metabolism*; D011475:Prosthesis Failure; D012044:Regression Analysis; D012117:Resins, Synthetic / Q000737:chemistry* / Q000378:metabolism*; D013229:Stearic Acids / Q000737:chemistry / Q000378:metabolism; D013242:Sterilization; D013997:Time Factors
chemical_list: D001672:Biocompatible Materials; D011095:Polyethylenes; D012117:Resins, Synthetic; D013229:Stearic Acids; C111601:ultra-high molecular weight polyethylene; C031183:stearic acid