PERFORMANCE ANALYSIS OF HEXAGONAL UNIT CELL STENT DESIGN AND SINGLE-LAYERED MANUFACTURABILITY WITH FDM

The usability of polymer stents is questioned according to the results obtained from preliminary clinical studies for biodegradable polymer-based stents developed after drug-eluting stents. Due to the high strut thickness and weak mechanical properties of polymer stents, research continues on the creation of new models by improving the design and material. The dog-boning in balloon-expanded stents damages the intimal and medial layers within the artery. This damage causes neointimal hyperplasia and restenosis in the early period. During the balloon expansion of the Palmaz-Schatz unit cell model, which is one of the metallic stent geometries, dog-boning and foreshortening rates occur. In this study, a new design was carried out in hexagonal unit stent geometry from PLLA material, taking into account the geometry formed by the expansion of the Palmaz-Schatz stent geometry. The dog-boning and foreshortening ratio of the hexagonal stent designed in thin strut thickness was determined by finite element simulation. In addition, vessel injury in the three-layered artery and calcified plaque structure was measured during stent expansion. The dog-boning and foreshortening ratio of the stent with hexagonal geometry is reduced compared to the Palmaz-Schatz model. However, after the 3D printing of the hexagonal stent geometry was produced as a single layer by fused deposition modeling from PLA/PHA blends, it was wrapped on a heating tubular table and brought into the stent form.