Aromatic Thermosetting Copolyester (ATSP) / UHMWPE Blends with Improved Wear Properties and Biocompatibility

Abstract

Despite the recognized success and worldwide acceptance of ultrahigh molecular weight polyethylene (UHMWPE) for total joint arthroplasty, the generation of UHMWPE wear debris from the articulating surface is of major concern and limits the longevity of the artificial joint device. Blends of UHMWPE with an aromatic thermosetting copolyester (ATSP) at 50:50 volume ratio using poly(ethylene-co-acrylic acid) (PEA) as a compatibilizer were developed to address this problem. The amount of PEA was 0, 5, 10, 15 and 20 weight percent of the weight of ATSP, respectively. The wear properties of these blends were evaluated by a pin-on-disk wear test in which an ASTM F-75 cobalt-chromium alloy disk was chosen as a counterface and sterile filtered bovine serum diluted in deionized water to 75% (volume) was used as a lubricant. The wear tests from 0.2 to 3 million cycles showed that UHMWPE/ATSP blend with 10 wt% PEA had average weight loss smaller than UHMWPE and comparable to crosslinked UHMWPE. The wear debris study indicated that UHMWPE/ATSP blend with 10 wt% PEA created a smaller size percentage of the wear debris particles in the biologically active range than UHMWPE and crosslinked UHMWPE. The direct-contact cytotoxicity tests showed that ATSP and UHMWPE/ATSP blend with 10 wt% PEA were not toxic.