Meyer Dominik Christoph, Felix Evelyne, Ruffieux Kurt, Gerber Christian
Department of Orthopaedics, University of Zürich;, Zürich, Switzerland.
Arthroscopy. 2004 Feb;20(2):185-90. doi: 10.1016/j.arthro.2003.11.014.
Absorbable implant materials offer various advantages but are mechanically far weaker than metals. Despite known temperature dependence of the biomechanical properties of these materials, mechanical testing has almost exclusively been performed at room temperature in the literature. In this study, the difference in mechanical performance at room and body temperature was assessed in vitro at different test speeds.
Biomechanical bench study.
Five absorbable suture anchor models were held in a metallic holder and loaded under tension using 0.5-mm steel wires until failure. Testing temperature was 20 degrees C +/- 1 degrees C or 37 degrees C +/- 1 degrees C, test speed was 50 mm/min or 5 mm/min. Tensile load at failure and failure mode were recorded. To test creep behavior, a constant load of 100 N was applied, and time to failure was recorded at both temperatures.
Both raising the temperature and decreasing test speed significantly (P <.0001) impaired the mechanical performance of the tested implants. Increase of temperature (20 degrees C to 37 degrees C) resulted in a decrease of the maximal failure strength by up to 40% and decreased time to failure by up to 98% under static load. At 37 degrees, decreasing the test speed from 50 to 5 mm/min lowered the load to failure by up to 18%. Failure of the anchors always occurred by eyelet cutout of the wire.
The lower the test speed, the higher is the influence of the testing temperature. Testing of implants at room temperature instead of body temperature may falsely improve test results by a factor of up to 50 under static load. Therefore, testing absorbable implants at body temperature seems mandatory, preferably at slow test speeds.
可吸收植入材料具有多种优势，但在机械性能方面远弱于金属。尽管已知这些材料的生物力学性能具有温度依赖性，但文献中几乎所有的机械测试都是在室温下进行的。在本研究中，在体外不同测试速度下评估了室温与体温时的机械性能差异。
生物力学实验台研究。
将五个可吸收缝线锚钉模型固定在金属夹具中，使用0.5毫米钢丝进行拉伸加载直至失效。测试温度为20℃±1℃或37℃±1℃，测试速度为50毫米/分钟或5毫米/分钟。记录失效时的拉伸载荷和失效模式。为测试蠕变行为，施加100 N的恒定载荷，并记录两个温度下的失效时间。
升高温度和降低测试速度均显著（P<.0001）损害了受试植入物的机械性能。温度升高（从20℃至37℃）导致最大失效强度降低高达40%，在静载下失效时间减少高达98%。在37℃时，将测试速度从50毫米/分钟降低至5毫米/分钟，使失效载荷降低高达18%。锚钉的失效总是通过钢丝的小孔切口发生。
测试速度越低，测试温度的影响越大。在室温而非体温下测试植入物可能会在静载下错误地将测试结果提高多达50倍。因此，在体温下测试可吸收植入物似乎是必要的，最好采用慢速测试速度。
