Impact of lipid-induced degradation on the mechanical properties of ultra-high molecular weight polyethylene for joint replacements.
Gamma or electron beam irradiation of ultra-high molecular weight polyethylene (UHMWPE) used in artificial joints for sterilization and/or crosslinking purposes generates free radicals in the material, which causes long-term oxidative degradation of UHMWPE. Recently, another mechanism for the degradation of UHMWPE by the absorption of lipids during in vivo clinical use was proposed. However, knowledge on lipid-induced degradation is quite limited, compared with that on radical-induced degradation. In this study, lipid-induced degradation was simulated using squalene absorption and subsequent accelerated aging, and its impact on the mechanical properties of UHMWPE was evaluated. The simulated lipid-induced degradation caused an increased elastic modulus and decreased elongation with maximum degradation at the surfaces. These results imply that degradation of UHMWPE may occur during in vivo long-term use, even if free radicals are completely eliminated. Therefore, further investigation is required to clarify the impact of lipid-induced degradation on clinical outcomes, such as the wear and fatigue characteristics of UHMWPE components.
National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan. Electronic address: sakoda@nihs.go.jp.
Hideyuki
H
Sakoda
National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan.
Shingo
S
Niimi
D065966:Absorption, Physicochemical; D019643:Arthroplasty, Replacement; D008055:Lipids / Q000737:chemistry*; D010084:Oxidation-Reduction; D011095:Polyethylenes / Q000737:chemistry* / Q000378:metabolism*; D013185:Squalene / Q000737:chemistry; D013314:Stress, Mechanical; D013997:Time Factors
D008055:Lipids; D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene; D013185:Squalene
Degradation; Lipids; Mechanical properties; UHMWPE