Ceramic Physics Laboratory and Research Institute for Nanoscience, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan.
Department of Orthopedic Surgery, Osaka University Medical School, 2-2 Yamadaoka, Suita 565-0871 Osaka, Japan.
J Mech Behav Biomed Mater. 2014 Mar;31:86-99. doi: 10.1016/j.jmbbm.2013.02.019. Epub 2013 Apr 20.
Structural modifications were studied at the molecular scale in two highly crosslinked UHMWPE materials for hip-joint acetabular components, as induced upon application of (uniaxial) compressive strain to the as-manufactured microstructures. The two materials, quite different in their starting resins and belonging to different manufacturing generations, were a single-step irradiated and a sequentially irradiated polyethylene. The latter material represents the most recently launched gamma-ray-irradiated polyethylene material in the global hip implant market. Confocal/polarized Raman spectroscopy was systematically applied to characterize the initial microstructures and the microstructural response of the materials to plastic deformation. Crystallinity fractions and preferential orientation of molecular chains have been followed up during in vitro deformation tests on unused cups and correlated to plastic strain magnitude and to the recovery capacity of the material. Moreover, analyses of the in vivo deformation behavior of two short-term retrieved hip cups are also presented. Trends of preferential orientation of molecular chains as a function of residual strain were similar for both materials, but distinctly different in their extents. The sequentially irradiated material was more resistant to plastic deformation and, for the same magnitude of residual plastic strain, possessed a higher capacity of recovery as compared to the single-step irradiated one.
研究了两种高度交联的超高分子量聚乙烯髋关节髋臼部件材料在分子尺度上的结构变化，这些变化是在制造的微观结构上施加（单轴）压缩应变后产生的。这两种材料在起始树脂方面差异很大，属于不同的制造代，分别为一步辐照聚乙烯和序贯辐照聚乙烯。后一种材料是目前全球髋关节植入物市场上最新推出的γ射线辐照聚乙烯材料。共聚焦/偏振拉曼光谱系统地应用于表征初始微观结构和材料对塑性变形的微观结构响应。在对未使用的杯子进行体外变形试验期间，跟踪了结晶度分数和分子链的择优取向，并将其与塑性应变幅度和材料的恢复能力相关联。此外，还介绍了对两个短期回收髋关节杯的体内变形行为的分析。两种材料的分子链择优取向随残余应变的趋势相似，但程度明显不同。序贯辐照材料对塑性变形的抵抗力更强，与单步辐照材料相比，在相同的残余塑性应变幅度下，具有更高的恢复能力。
