Abstracts Posters SICOT-SOF meeting Gothenburg 2010 _2_

Poster
Topic: General Orthopaedics
Abstract number: 25053
REAL-TIME AGING AND THE ELUTION OF VITAMIN E-STABILIZED
CROSSLINKED UHMWPE
Orhun MURATOGLU, Shannon ROWELL, Ebru ORAL
Massachusetts General Hospital, Boston (UNITED STATES)
Vitamin E is used to maintain oxidative stability in crosslinked UHMWPE for total
joints. It can be blended with UHMWPE powder with subsequent irradiation of the
consolidated mixture or diffused into UHMWPE after irradiation. Because vitamin E
hinders crosslinking, its concentration during blending is limited to 0.2-0.3wt% to
achieve high cross-link density and low wear rate. We compared the oxidative
stability of blended and diffused crosslinked UHMWPEs by accelerated and real-time
aging. Vitamin E blends (0.02 , 0.05, 0.1wt%) were irradiated (100, 150, 200kGy) .
Irradiated UHMWPEs (100, 150kGy) were diffused with vitamin E (~1.5wt%) and
gamma sterilized. Blocks were real-time aged for 36 months in water at 40°C or
accelerated aged at 70C for 2 weeks at 5 atm. of oxygen. Accelerated aging resulted
in significant oxidation in irradiated, unstabilized control UHMWPEs but did not result
in oxidation in the vitamin E-stabilized crosslinked UHMWPEs. In contrast, at 36
months of real-time aging, irradiated blends showed significantly higher oxidation
than before aging, whereas post-irradiation diffused UHMWPE showed no oxidation.
Thus, real-time aging differentiated among vitamin E-stabilized, radiation crosslinked
UHMWPEs prepared by different methods. During real-time aging, the vitamin E
concentration of the diffused blocks decreased and the initial non-uniform profile with
high surface concentration became uniform, equilibrating at ~0.7 wt% vitamin E at 36
months. We attribute this to the difference in solubility of vitamin E in UHMWPE at
40°C, compared to that at the initial diffusion tem perature of 120°C. Nevertheless,
this material showed oxidative resistance up to 36 months.
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