BACKGROUND:Accelerated hydrothermal aging has long been one of the most widely accepted quality control tests for simulating low-temperature degradation (LTD) in zirconia-containing implants used in total hip arthroplasty (THA). However, it is still unclear how much consistency there is between theexperimental prediction from the internationally-standardized tests and the actual measurements from surgically-removed implants after a long period of implantation. This question is fundamentally related to a lack of understanding of mechanical/tribological contribution to the in-vivo LTD kinetics. OBJECTIVE:The main purpose of this study is to validate the clinical relevance of standardized accelerated aging by comparing artificially-aged and in-vivo used prostheses, and to clarify the long-term effects of in-vivo mechanics/tribology on the LTD progression upon service in the body environment. METHODS:Surface magnitudes of phase transformation and residual stress in zirconia femoral head retrievals (13.1–18.4 yrs) were evaluated by using confocal Raman microspectroscopy. RESULTS:The long-term aging behavior in unworn head surface was in agreement with the experimental prediction estimated as 1 h aging at 134 °C = 4 years in-vivo. However, the current aging protocols based on ASTM and ISO criteria were not accurately predictive for the worn surfaces, and the tribologically-induced phase transformation and tensile stress were up to 6.5-times and 3.3-times higher than the environmentally-induced ones. CONCLUSION:Our study suggests that wear/scratching, frictional heating, tribochemical reactions, and metal transfer may become far more intense triggers to phase transformation than the mere exposure to body fluid.

中文翻译：

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人工老化能否正确预测氧化锆髋关节假体的长期体内降解行为？

背景：加速水热老化长期以来一直是模拟全髋关节置换术（THA）所用含氧化锆的植入物的低温降解（LTD）的最广泛接受的质量控制测试之一。然而，目前尚不清楚国际标准化测试的实验预测与长时间植入后的手术切除植入物的实际测量值之间有多少一致性。这个问题从根本上与缺乏对体内LTD动力学的机械/摩擦学贡献的理解有关。目的：本研究的主要目的是通过比较人工老化和体内使用的假体，验证标准化加速老化的临床意义，并阐明体内力学/摩擦学对LTD发展的长期影响。方法：使用共聚焦拉曼光谱法评估氧化锆性股骨头修复术（13.1-18.4年）中相变和残余应力的表面强度。结果：未佩戴的头部表面的长期老化行为与实验预测相符，在134°C下老化1 h =体内4年。但是，当前基于ASTM和ISO标准的老化协议无法准确预测磨损的表面，摩擦引起的相变和拉伸应力分别比环境引起的高6.5倍和3.3倍。结论：我们的研究表明，磨损/刮擦，摩擦加热，摩擦化学反应，