Department of Mechanical Engineering, University of California, Berkeley, 2121 Etcheverry Hall, Berkeley, CA 94720, USA.
J Mech Behav Biomed Mater. 2011 Oct;4(7):1033-45. doi: 10.1016/j.jmbbm.2011.03.012. Epub 2011 Mar 11.
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.
本研究评估了在各种临床相关的交联超高分子量聚乙烯中，疲劳裂纹扩展阻力、耐磨性和抗氧化稳定性之间的权衡。高度交联的再熔融材料表现出良好的氧化和耐磨性能，但疲劳裂纹扩展阻力降低。高度交联的退火材料表现出良好的耐磨和疲劳性能，但抗氧化性差。适度交联的再熔融材料表现出良好的抗氧化性，但耐磨性和疲劳性中等。增加辐射剂量可提高耐磨性，但降低疲劳裂纹扩展阻力。退火比再熔融降低疲劳阻力的效果较小，但使材料易受氧化。这似乎是因为交联后在熔点以下退火会增加层片的体积分数和尺寸，但不能中和所有自由基。相反，交联后再熔融似乎可以消除自由基，但由于交联网络的限制，重新形成的层片数量较少且尺寸较小，导致疲劳裂纹扩展阻力差。这是第一项同时评估各种临床相关超高分子量聚乙烯的疲劳裂纹扩展、磨损、氧化和微观结构的研究。我们在疲劳、磨损和氧化性能方面的权衡对于材料在全关节置换中的长期成功至关重要。
