Numerical investigation of flexibility: Open-cell versus closed-cell stent designs

This numerical study investigates the advantages/disadvantages of two commercial coronary stent designs for its flexibility. Coronary stents are medical devices used to treat atherosclerotic coronary arteries. A variety of geometrical designs of stents are available in the market which can be broadly classified as open cell and closed cell stent designs based on ‘link’ positioning. Flexibility, one of the factors impacting implantation success, is influenced by stent geometry, particularly the ‘link’. In this study flexibility of two commercial stent designs Supraflex™ (Open-cell) and Yukon Choice (Closed-cell) are investigated using Finite Element Analysis package ANSYS workbench. Realistic and idealized stent models are used for simulation to measure the performance in terms of bending moment versus curvature index plot. Results suggest an upper hand for Stent T, as Stent S demonstrated direction-specific bending nature. Results also underscore the necessity of realistic modeling of geometry as ideal models over/underestimated the stress and bending in comparison to realistic models. The study highlights the drawbacks of the two-ring ‘unit cell’ model for flexibility measurement and recommends a model based on link positioning. The results throw light on the importance of the positioning of links in improving stent flexibility.