Ceramic Physics Laboratory, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan; Department of Orthopedic Surgery, Tokyo Medical University, 6-7-1 Nishi-Shinjuku, Shinjuku-ku, 160-0023 Tokyo, Japan; The Center for Advanced Medical Engineering and Informatics, Osaka University, Yamadaoka, Suita, 565-0871 Osaka, Japan; Department of Molecular Cell Physiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kamigyo-ku, 465 Kajii-cho, Kawaramachi dori, 602-0841 Kyoto, Japan; The Center for Advanced Insect Research Promotion (CAIRP), Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan.
Department of Medical Engineering for Treatment of Bone and Joint Disorders, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0854, Japan.
J Mech Behav Biomed Mater. 2018 Jun;82:168-182. doi: 10.1016/j.jmbbm.2018.03.021. Epub 2018 Mar 17.
Experimental evidence demonstrates that a loss of stoichiometry at the surface of oxide bioceramic femoral heads enhances the oxidation rate of polyethylene acetabular liners in artificial hip joints. Contradicting the common notion that ceramics are bioinert, three independent experiments confirmed substantial chemical interactions between the ceramic femoral heads and their polyethylene counterparts. The experiments reported herein included hydrothermal tests, frictional tests, and hip-simulator experiments. It was discovered that oxide and non-oxide femoral heads differently affected the oxidation processes at the surface of the polyethylene liners, all other testing parameters being equal. Analytical data from X-ray photoelectron (XPS), cathodoluminescence (CL), Fourier-transform infrared (FTIR), and Raman spectroscopies unequivocally and consistently showed that the oxidation rate of polyethylene liners was greater when coupled with oxide as opposed to non-oxide ceramic heads. XPS analyses of O-Al-O bond fractions at the surface of a zirconia-toughened alumina (ZTA) short-term (20 months in vivo) femoral heads retrieval showed a 50% reduction in favor of oxygen vacancy O-Al-V and hydroxylated Al-O-H bonds. Off-stoichiometry drifts were confirmed in vitro under both static and dynamic conditions. They triggered oxidation and tangibly affected an advanced highly cross-linked sequentially irradiated and annealed ultra-high molecular weight polyethylene (UHMWPE) liner (increase in oxidation index up to ΔOI1.2 after 5 × 10 cycles under dynamic swing conditions). Second-generation UHMWPE liners infused with vitamin E were also affected by the free flow of oxygen from the oxide femoral heads, although to a lesser extent. The fundamental findings of this study, which were also confirmed on retrievals, call for revised standards in material design and testing. Adopting these new criteria will provide an improved understanding of the importance of off-stoichiometry at the head/liner interface and may lead to significant extensions in artificial joint lifetimes.
实验证据表明，氧化物生物陶瓷股骨头表面的化学计量比损失会加速人工髋关节中聚乙烯髋臼衬里的氧化速率。与陶瓷惰性的普遍观点相反，三个独立的实验证实了陶瓷股骨头与其聚乙烯对应物之间存在大量的化学相互作用。本文报道的实验包括水热试验、摩擦试验和髋关节模拟器试验。研究发现，氧化物和非氧化物股骨头以不同的方式影响了聚乙烯衬里表面的氧化过程，所有其他测试参数均相同。X 射线光电子能谱（XPS）、阴极发光（CL）、傅里叶变换红外（FTIR）和拉曼光谱的分析数据明确且一致地表明，当与氧化物股骨头而非非氧化物陶瓷股骨头结合时，聚乙烯衬里的氧化速率更大。对氧化锆增韧氧化铝（ZTA）短期（体内 20 个月）股骨头取出物表面 O-Al-O 键分数的 XPS 分析表明，有利于氧空位 O-Al-V 和羟基化 Al-O-H 键的比例减少了约 50%。在静态和动态条件下均在体外确认了非化学计量漂移。它们引发了氧化，并明显影响了先进的高度交联、顺序辐照和退火的超高相对分子质量聚乙烯（UHMWPE）衬里（在动态摆动条件下，5×10 次循环后氧化指数增加至ΔOI~1.2）。第二代注入维生素 E 的 UHMWPE 衬里也受到来自氧化物股骨头的自由氧流的影响，尽管程度较小。本研究的基本发现也在回收物中得到了证实，呼吁对材料设计和测试标准进行修订。采用这些新标准将更好地理解股骨头/衬里界面处非化学计量比的重要性，并可能导致人工关节寿命的显著延长。
