Mathys Ltd. Bettlach, Güterstrasse 5, CH-2544 Bettlach, Switzerland.
Biomaterials. 2010 May;31(13):3643-8. doi: 10.1016/j.biomaterials.2010.01.076. Epub 2010 Feb 9.
Wear and oxidative degradation may limit the life span of UHMWPE implants. Cross-linking and stabilisation by vitamin E are proposed to overcome wear and degradation. The present investigation takes a close look to the oxidative behaviour of cross-linked and stabilised UHMWPE. First, the consolidated vitamin E stabilised UHMWPE was qualified in terms of microstructure and homogeneity of the distribution of the additive to be suitable for oxidation profiles over the entire section. Then cross-linked samples with five different concentrations of vitamin E (nil to 1.0%) underwent two different ageing protocols. The first was under pressurized oxygen at 70 degrees C, as defined in the ASTM F 2003 standard with a prolonged period of 60 days, the second was in 5% aqueous hydrogen peroxide solution with iron (III) chloride as catalyst at 50 degrees C. The first accelerated ageing protocol showed that a vitamin E concentration as low as 0.05% is effective to protect irradiated highly cross-linked UHMWPE against oxidation when exposed direct to oxygen. Vitamin E stabilised, highly cross-linked UHMWPE exhibits therefore no oxidation potential origination from the irradiation treatment. Analysis of samples treated by the second chemical ageing yielded, that vitamin E is effective to prolong initial stability against a supplementary attack of hydrogen peroxide and reactive radicals. The time period of stability against the aggressive hydrogen peroxide solution increases with increasing vitamin E content. However, even 0.05% have a marked stabilisation effect. Therefore, such small additions of vitamin E are effective to protect the UHMWPE material against a supplementary exposure to in vivo oxidation after the irradiation treatment. In conclusion, vitamin E shields cross-linked UHMWPE for orthopaedic application against oxidation in the heat of consolidation, during irradiation treatment and finally while implanted in the human body.
磨损和氧化降解可能会限制超高分子量聚乙烯植入物的使用寿命。通过添加维生素 E 进行交联和稳定化被认为可以克服磨损和降解。本研究密切关注交联和稳定化的超高分子量聚乙烯的氧化行为。首先，对经过维生素 E 稳定化的固结超高分子量聚乙烯进行了微观结构和添加剂分布均匀性的质量评估，以确保其适合进行整个截面的氧化分析。然后，对五种不同浓度维生素 E（0%到 1.0%）的交联样品进行了两种不同的老化方案处理。第一种方案是在 ASTM F 2003 标准规定的 70°C 下进行加压氧气处理，处理时间延长至 60 天；第二种方案是在 50°C 下，以氯化铁为催化剂，在 5%的双氧水溶液中进行处理。第一种加速老化方案表明，即使维生素 E 的浓度低至 0.05%，也可以有效地保护受辐照的高度交联的超高分子量聚乙烯免受直接暴露于氧气时的氧化。因此，经维生素 E 稳定化和高度交联的超高分子量聚乙烯在辐照处理后，不会产生源自辐照处理的氧化潜力。对经第二种化学老化处理的样品进行分析表明，维生素 E 可以有效地延长初始稳定性，防止过氧化氢和反应性自由基的进一步攻击。对过氧化氢溶液的稳定性时间随着维生素 E 含量的增加而增加。然而，即使添加 0.05%的维生素 E，也具有显著的稳定化效果。因此，这种小剂量的维生素 E 可以有效地保护超高分子量聚乙烯材料免受辐照处理后在体内再次暴露于氧化的影响。总之，维生素 E 可以保护交联的超高分子量聚乙烯材料在热固结、辐照处理以及最终植入人体过程中免受氧化。
