This study evaluated the tradeoffs amongst
fatigue crack propagation resistance, wear resistance, and oxidative stability in a wide variety of clinically-relevant cross-linked
ultra-high molecular weight polyethylene. Highly cross-linked re-melted materials showed good oxidation and wear performance, but diminished
fatigue crack propagation resistance. Highly cross-linked annealed materials showed good wear and
fatigue performance, but poor oxidation resistance. Moderately cross-linked re-melted materials showed good oxidation resistance, but moderate wear and
fatigue resistance. Increasing radiation dose increased wear resistance but decreased
fatigue crack propagation resistance. Annealing reduced
fatigue resistance less than re-melting, but left materials susceptible to oxidation. This appears to occur because annealing below the melting temperature after cross-linking increased the volume fraction and size of lamellae, but failed to neutralize all
free radicals. Alternately, re-melting after cross-linking appeared to eliminate
free radicals, but, restricted by the network of cross-links, the re-formed lamellae were fewer and smaller in size which resulted in poor
fatigue crack propagation resistance. This is the first study to simultaneously evaluate
fatigue crack propagation, wear, oxidation, and microstructure in a wide variety of clinically-relevant ultra-high. The tradeoff we have shown in
fatigue, wear, and oxidation performance is critical to the material's long-term success in
total joint replacements.