Degradation of magnesium alloy stents: finite element analyses and preliminary experimental tests.

Biodegradable magnesium alloy stents (MAS) have attached lots of attentions in recent years because MAS can reduce the long-term incompatibility between vessels and permanent stent platforms. However, the insufficient scaffolding ability for the vessel due to corrosion is a main limitation of MAS. Following the previous finite element analysis (FEA) work of an optimized MAS design, this study simulated the corrosion process of two MAS models with the help of a proposed biodegradable material model. In particular, two FEA models according to the optimized MAS design and a patent design were compared for their property of corrosion resistance. After that, corrosion experiments were carried out to preliminarily verify the simulation using two MAS samples based on the same designs. The simulation showed that the stent models corroded with both uniform and stress corrosion mechanisms. The former mechanism led to a "layer by layer" corrosion phenomenon and the former led to early breaks on the stent struts. The simulation also predicted the optimized design would have better corrosion resistance than the patent design. The experiments fairly verified the simulated corrosion phenomenon and proved the better corrosion resistance of the optimized design. The FEA model can provide an effective tool for design and improvement of novel biodegradable MAS.