Kurtz Steven M, Mazzucco Dan, Rimnac Clare M, Schroeder Dave
Exponent, Inc., 3401 Market St., Suite 300, Philadelphia, PA 19104, USA.
Biomaterials. 2006 Jan;27(1):24-34. doi: 10.1016/j.biomaterials.2005.05.102.
Solid-state deformation processing is a promising technique for modifying the physical and mechanical properties of highly crosslinked ultra-high molecular weight polyethylene (UHMWPE) beyond simple thermal treatment cycles that have been employed previously. This study evaluates anisotropy and oxidative resistance in a novel, radiation crosslinked (50 kGy) UHMWPE material (ArComXL: Biomet, Inc., Warsaw, IN), incorporating solid-state, deformation processing by extrusion below the melt transition for application in total hip arthroplasty. Tensile, compression, and small punch tests were conducted to evaluate the material properties in the three principal axes of the resulting material. Furthermore, short-term oxidative resistance was evaluated using Fourier transform infrared spectroscopy and the small punch test in conjunction with accelerated shelf aging protocols. The results of this testing indicate that the material is anisotropic, with significantly enhanced strength oriented along the long axis of the rod. For certain other properties, the magnitude of the anisotropy was relatively slight, especially in the elastic regime, in which only a 20% difference was noted between the long axis of the rod and the orthogonal, radial direction. The highly crosslinked material contains detectable free radicals, at a concentration that is 90% less than control, gamma inert sterilized UHMWPE. An unexpected finding of this study was evidence of oxidative stability of the deformation-processed material, even after 4 weeks of accelerated aging in a pressure vessel containing five atmospheres of oxygen (ASTM F2003), which resulted in macroscopic embrittlement of the control material. The oxidative stability observed in ArComXL suggests that the deformation-processed material may be suitable for air-permeable packaging and gas sterilization, which has thus far been reserved for remelted highly crosslinked UHMWPE.
固态变形加工是一种很有前景的技术，可用于改变高度交联的超高分子量聚乙烯（UHMWPE）的物理和机械性能，这超出了以往使用的简单热处理循环的范畴。本研究评估了一种新型的、经辐射交联（50 kGy）的UHMWPE材料（ArComXL：Biomet公司，印第安纳州华沙）的各向异性和抗氧化性，该材料通过在低于熔融转变温度下进行挤压的固态变形加工，用于全髋关节置换术。进行了拉伸、压缩和小冲头试验，以评估所得材料三个主轴方向的材料性能。此外，结合加速货架老化方案，使用傅里叶变换红外光谱和小冲头试验评估了短期抗氧化性。该测试结果表明，该材料具有各向异性，沿棒材长轴方向的强度显著增强。对于某些其他性能，各向异性的程度相对较小，尤其是在弹性范围内，棒材长轴与正交的径向方向之间仅存在20%的差异。这种高度交联的材料含有可检测到的自由基，其浓度比对照的γ射线惰性灭菌UHMWPE低90%。本研究的一个意外发现是，即使在含有五个大气压氧气的压力容器中加速老化4周后（ASTM F2003），变形加工材料仍具有氧化稳定性，而对照材料则出现了宏观脆化。在ArComXL中观察到的氧化稳定性表明，变形加工材料可能适用于透气包装和气体灭菌，而迄今为止，这仅适用于重新熔融的高度交联UHMWPE。
