Abstract
Concerns about reduced strength, fatigue resistance, and oxidative stability of highly crosslinked UHMWPE have limited the acceptance of these materials for TKR. It was hypothesized that a new crosslinked UHMWPE stabilized with vitamin E would substantially improve wear performance and resistance to oxidative degradation without compromising mechanical properties. The purpose of this study was to comprehensively test this hypothesis in vitro.
GUR1020 was machined from isostatic molded bar-stock, crosslinked with 100 kGy, and then doped with vitamin E. This material was compared to direct molded GUR1050 UHMWPE. Both materials were gamma irradiation sterilized as for clinical use. Small punch testing, crack growth rate fatigue testing and oxidation index measurements were performed on each material before and after accelerated aging. Knee simulator testing evaluated wear of each material for 5-million walking cycles. CR knees were tested on a 6-station AMTI knee simulator; PS knees were tested on two 4-station Instron-Stan-more knee simulators. Statistical differences in all metrics were evaluated for significance with ANOVA (p < 0.05).
After 4-week accelerated aging, the control material showed elevated oxidation, loss of small punch mechanical properties and decreased fatigue crack growth resistance. In contrast, the vitamin E stabilized material had minimal changes in these properties. Further, the vitamin E stabilized material exhibited 85% reduction in wear for both the CR and PS designs.
Highly crosslinked UHMWPE stabilized with vitamin E appears to be promising for use as a bearing surface in TKA.
Correspondence should be addressed to ISTA Secretariat, PO Box 6564, Auburn, CA 95604, USA. Tel: 1-916-454-9884, Fax: 1-916-454-9882, Email: ista@pacbell.net
