Optimizing structural design on biodegradable magnesium alloy vascular stent for reducing strut thickness and raising radial strength

Abstract

Thinner biodegradable magnesium alloy stents (BMgSs) afford faster endothelialisation to delay degradation and better clinical performance. However, compared with traditional non-degradable stents, thin-walled BMgS structures are prone to challenges, such as insufficient support capacity and fracture, during immediate expansion due to low elastic modulus and ultimate elongation. In this study, a thin-walled BMgS structure was optimised. A ZE21B alloy with large breaking elongation and excellent mechanical properties served as the basis of our BMgS. Using finite element analysis, the support ring structure of a typical stent BioMatrix was optimised using response surface models, and an optimised configuration of a thin-walled BMgS was obtained. The optimised thin-walled stent (100-μm thick) had a radial strength comparable to that of the original thick-walled stent (150-μm thick); and the maximum principal strain is significantly decreased (0.207 vs 0.283). The balloon dilation and radial strength tests were validated. Experiments showed that the optimised stent had sufficient deformation stability during the crimping and expansion processes, and there was no strut fracture. Furthermore, the maximum principal stress area of the stent and the damage to the stenotic artery were significantly improved after optimisation.

Keywords

• Structural design
• Finite element analysis
• Biodegradable magnesium alloy stents
• Radial strength