Shibata Nobuyuki, Tomita Naohide
Department of Human Engineering, National Institute of Industrial Health, 6-21-1, Nagao, Tama-ku, Kawasaki 214-8585, Japan.
Biomaterials. 2005 Oct;26(29):5755-62. doi: 10.1016/j.biomaterials.2005.02.035. Epub 2005 Apr 19.
Although addition of an antioxidant (alpha-tocopherol) is reported to prevent delamination in ultrahigh molecular weight polyethylene (UHMWPE) knee components, contribution of alpha-tocopherol as an antioxidant to the improvement of long-term fatigue performance of UHMWPE is an unknown mechanism. To solve this problem, bi-directional sliding fatigue tests were performed for gamma-irradiated (25 kGy), gamma-irradiated (25 kGy) with 0.3 wt% alpha-tocopherol added, and gamma-irradiated (25 kGy) with 0.3 wt% tocopheryl acetate added UHMWPE specimens. Internal defect initiation was quantified with scanning acoustic tomography (SAT). Also, oxidation index and crystallinity were obtained from infrared absorption spectra measured using Fourier transform infrared (FT-IR) microscopy. Only gamma-irradiated UHMWPE specimens resulted in severe fatigue fractures. alpha-Tocopherol-added UHMWPE specimens showed significantly lower projected area ratio of defects (1.80+/-0.82) than did gamma-irradiated (7.0+/-2.29) and tocopheryl acetate-added ones (8.50+/-2.01). The oxidation index of gamma-irradiated UHMWPE specimens (0.111+/-0.0052) was extremely higher compared to those of doped ones; 0.0179+/-0.0026 and 0.0144+/-0.0069 for alpha-tocopherol-added and tocopheryl acetate-added ones, respectively. The crystallinity of gamma-irradiated UHMWPE specimens (57.5+/-1.16) was lower compared to those of doped ones; 60.3+/-0.72 and 60.4+/-1.38 for alpha-tocopherol-added and tocopheryl acetate-added ones, respectively. The incorporation of alpha-tocopherol significantly improves the long-term fatigue performance of gamma-irradiated UHMWPE with oxidation stability. Also, the addition of alpha-tocopherol controls macromolecular structures resulting in the improvement of fatigue performance of UHMWPE.
虽然据报道添加抗氧化剂（α-生育酚）可防止超高分子量聚乙烯（UHMWPE）膝关节部件分层，但α-生育酚作为抗氧化剂对改善UHMWPE长期疲劳性能的作用机制尚不清楚。为了解决这个问题，对γ辐照（25 kGy）、添加0.3 wt%α-生育酚的γ辐照（25 kGy）以及添加0.3 wt%醋酸生育酚的γ辐照（25 kGy）的UHMWPE试样进行了双向滑动疲劳试验。用扫描声学断层扫描（SAT）对内部缺陷萌生进行量化。此外，氧化指数和结晶度通过使用傅里叶变换红外（FT-IR）显微镜测量的红外吸收光谱获得。仅γ辐照的UHMWPE试样出现严重疲劳断裂。添加α-生育酚的UHMWPE试样的缺陷投影面积比（1.80±0.82）显著低于γ辐照的（7.0±2.29）和添加醋酸生育酚的（8.50±2.01）。γ辐照的UHMWPE试样的氧化指数（0.111±0.0052）比掺杂试样的高得多；添加α-生育酚和添加醋酸生育酚的试样分别为0.0179±0.0026和0.0144±0.0069。γ辐照的UHMWPE试样的结晶度（57.5±1.16）低于掺杂试样；添加α-生育酚和添加醋酸生育酚的值分别为60.3±0.72和60.4±1.38。α-生育酚的加入显著提高了γ辐照的UHMWPE的长期疲劳性能和氧化稳定性。此外，α-生育酚的添加控制了大分子结构，从而改善UHMWPE的疲劳性能。
