LAUSR

BACKGROUND The aim of this study is to determine the influence of crosslinking and addition of 0.3 wt% vitamin E in a polyethylene rim on its mechanical damage and oxidation caused by impingement. METHODS Six ultrahigh-molecular weight polyethylene samples were studied (control; crosslinked; vitamin-E containing; crosslinked and vitamin-E containing; aged control; and aged crosslinked and vitamin-E containing). Crosslinking was attained by irradiation with a 300 kGy electron beam; vitamin E incorporation was at 0.3 wt%; and aging was performed through forced oxidation for 14 days. Resistance to impingement was evaluated by stereoscopic observations, three-dimensional measurements, and oxidation measurements by Fourier transform infrared spectroscopy. FINDINGS Rim breakage (delamination and fracture) due to impingement was observed only for the aged control specimen. In contrast, crosslinked specimens containing vitamin E showed no failure of the rim after aging. The addition of vitamin E to polyethylene suppressed its oxidation and reduced the oxidation caused by crosslinking or impingement. The impingement resistance of the control sample deteriorated upon oxidation, whereas that of vitamin E-containing crosslinked polyethylene remained high due to the antioxidant property of vitamin E. INTERPRETATION Vitamin E-containing polyethylene showed a reduced risk of wear/breakage of polyethylene rims by impingement.