title: In Vivo Oxidative Stability Changes of Highly Cross-Linked Polyethylene Bearings: An Ex Vivo Investigation.
abstract: The development of highly cross-linked UHMWPEs focused on stabilizing radiation-induced free radicals as the sole precursor to oxidative degradation. However, secondary in vivo oxidation mechanisms have been discovered. After a preliminary post-operative analysis, we subjected highly cross-linked retrievals with 1-4 years in vivo durations and never-implanted controls to accelerated aging to predict the extent to which their oxidative stability was compromised in vivo. Lipid absorption, oxidation, and hydroperoxides were measured using infrared spectroscopy. Gravimetric swelling was used to measure cross-link density. After aging, all retrievals, except vitamin E-stabilized components, regardless of initial lipid levels or oxidation, showed significant oxidative degradation, demonstrated by subsurface oxidative peaks, increased hydroperoxides and decreased cross-link density, compared to their post-operative material properties and never-implanted counterparts, confirming oxidative stability changes.
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Shannon L
authors.initials: SL
authors.lastname: Rowell
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Reyes
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston, Massachusetts; Sahlgrenska University Hospital, Mölndal, Sweden; Harvard Medical School, Cambridge, Massachusetts.
authors.forename: Henrik
authors.initials: H
authors.lastname: Malchau
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston, Massachusetts; Harvard Medical School, Cambridge, Massachusetts.
authors.forename: Orhun K
authors.initials: OK
authors.lastname: Muratoglu
mesh_terms: D003432:Cross-Linking Reagents / Q000737:chemistry*; D006622:Hip Prosthesis; D006801:Humans; D007720:Knee Prosthesis; D008055:Lipids / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D011095:Polyethylenes / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013997:Time Factors; D014810:Vitamin E / Q000737:chemistry
chemical_list: D003432:Cross-Linking Reagents; D008055:Lipids; D011095:Polyethylenes; D011108:Polymers; C111601:ultra-high molecular weight polyethylene; D014810:Vitamin E; D010100:Oxygen
keywords: accelerated aging; oxidation; polyethylene (UHWMPE); retrievals; total joint arthroplasty