A comparative in vitro study of distinct and novel stent geometries on mechanical performances of poly-L-lactic acid cardiovascular stents

Background: Poly-L-lactic acid (PLLA) is one of the representative polymeric materials serving as bioresorbable stents (BRS) for cardiovascular disease due to its proper biodegradation, high biocompatibility, and adequate mechanical properties among polymer candidates for BRS. However, PLLA BRS as cardiovascular stents also have limitations because their mechanical properties including low radial strength and high elastic recoil are inferior to those of metallic-based BRS stents. Methods: In the study, we developed and manufactured distinct and novel types of stent geometries for investigating mechanical properties of thin-walled PLLA BRS (110 μm) for cardiovascular applications. Five key mechanical tests, including radial strength, crimping profile, flexibility, elastic recoil, and foreshortening were performed through a comprehensive analysis. In addition, we applied the finite element method for further validation and insight of mechanical behaviors of the PLLA BRS. Results: Results revealed that Model 2 had advantages in high flexibility as well as radial strengths, which would be a proper option for complex and acutely curved lesions. Model 3 would be an optimum selection for stent placement in mild target site due to its strength in minimum elastic recoil. Even though Model 4 showed the highest radial strength, finite element simulation showed that the geometry caused higher maximum stress than that of Model 2 and Model 3 during the crimping process. Model 1 showed the most vulnerable geometry among the tested models in both in vitro and finite element analysis. Conclusion: Such data may suggest potential guidance in regard to understanding the mechanical behaviors of PLLA BRS as not only applicable cardiovascular but also peripheral and intracranial stents.