Abstract
Introduction: Highly crosslinked UHMWPEs have been widely used in total hip replacements but have seen limited use at the knee due to concerns over strength characteristics. A new process, sequential irradiation and annealing, overcomes these limitations.
Materials and Methods: GUR 1020 polyethylene was sequentially crosslinked using three separate gamma radiation doses of 3 Mrad with an annealing step at 130 degrees C after each irradiation (SXL).
Wear was determined by weight loss under normal walking and stair climbing conditions (MTS knee simulator, 5 to 10 million cycles, 1 Hz, maximum load of 2600 N to 3800 N, alpha fraction bovine calf serum). Scorpio CR and PS knees were evaluated using SXL and UHMWPE gamma sterilized to 3 Mrad in nitrogen (gamma-N2). Oxidative challenge was in 5 atmospheres of oxygen at 70 degrees C for 14 days.
Results: Scorpio gamma-N2 CR knees under normal walking conditions had a weight loss of 32.6 +/− 1.9 mg/million cycles compared to 6.5 +/− 1.6 mg/million cycles for SXL (p of 0.024). With Scorpio PS knees, the wear was 33.5 +/− 1.6 for gamma-N2 versus 7.7 +/− 0.7 mg/million cycles for SXL (p of 0.000009) subject to stair climbing simulation. Wear particle size was similar for SXL and gamma-N2. SXL knees showed no effect of oxidative challenge in a 10 million-cycle knee study.
Discussion and Conclusions: Wear is reduced by 80 percent and 77 percent respectively for CR and PS knees with SXL compared to gamma-N2. SXL has high resistance to oxidative challenge as shown by the lack of effect on knee wear results.
Theses abstracts were prepared by Professor Roger Lemaire. Correspondence should be addressed to EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
