新型可降解镁合金血管支架的力学分析

Mechanical Analysis on a New Type of Biodegradable Magnesium-alloy Stent

近年来,可降解镁合金血管支架被用于动物实验和临床研究。文献报道镁合金支架具有良好的生物相容性,植入血管后能够被逐渐腐蚀降解,但与不锈钢相比,镁合金材料脆性大,塑性变形能力差。我们根据Biotronik公司的一种镁合金血管支架建立有限元模型,模拟其扩张和弯曲过程。有限元分析结果表明,扩张过程中支架中的最大应变值达到20%,超过了目前市场上提供的镁合金的最大延伸率。因此,为了使支架在扩张过程中不发生断裂,需要定制镁合金成分,并通过细化晶粒来提高材料延展性。在此基础上,才能研制出可用的镁合金血管支架。

Biodegradable magnesium-alloy stents have been employed in animal experiments and clinical researches in recent years. Magnesium-alloy stents have been reported to be biocompatible, and degradable due to corrosion after being implanted into blood vessel. However, magnesium alloy is brittle compared with stainless steel. This may cause strut break under large deformation. In this paper, a finite element model of magnesium-alloy stent was set up, with reference to pictures from Biotronik Corporation, to simulate the expanding and bending processes. The results of analysis show that the maximum strain during expanding reaches 20%, being greater than the elongation limit of the commercially available magnesium alloys. Therefore, to avoid strut breakage during expanding, the magnesium alloys should be custom-made. The plasticity of the material should be improved by grain refinement processes before practicable magnesium-alloy stents could be developed.