Computational and experimental investigation into mechanical performances of Poly-L-Lactide Acid (PLLA) coronary stents

Abstract

Poly-L-lactide Acid (PLLA), as a credible biodegradable polymer-based material, can provide a promising amount of degradation time for vessel remodeling. Served as a sort of reliable intravascular implants, PLLA stents are expected to provide sufficient scaffolding to the target arteries without generating too much recoil after deployment. Besides, the stress and strain distribution should be as homogeneous as possible, and the stent conformability in fitting to the nature curvature of the vessels needs to be guaranteed. In the present study, mechanical performances of a stent made of PLLA material were investigated based on 3-D finite element method (FEM) and experiment verification. Simulations contained several deformation steps: crimping, spring-back after crimping, expanding and spring-back after expanding. The stent's deformation and stress/strain distributions were analyzed. Several indexes including the radial recoil ratio after crimping and expanding to different sizes, the radial properties including radial strength, the radial stiffness and the collapse pressure were established. In vitro static loading experiments of the stent were conducted as the verification of the FEM results, and a good agreement between them was obtained. Moreover, simulation of three-point bending was performed to assess the bending flexibility of the stent, and bending stiffness was defined as a measurement of structure resistance to the bending deformation.

Mechanical Performance of PLLA Stent

“…Our results have shown that the elastic recoil for crimping was 13.9% and the one for expansion was 4.53%. This aligns with the observations by Wang et al [5], who reported a radial recoil for PLLA stent crimping and expansion as 10.87% and 4.19%, respectively.…”

“…This will, in turn, induce larger stress and strain in the arterial walls, leading to a greater risk of mechanical injury and tissue inflammation [5]. Our results have shown that the elastic recoil for crimping was 13.9% and the one for expansion was 4.53%.…”

Effect of working environment and procedural strategies on mechanical performance of bioresorbable vascular scaffolds

“…in air or in a submerged environment, to feed higher-level analyses of device performance, e.g. crimping, inflation, and load bearing capability [13,23]. However, viscoelastic-plastic polymers, such as pLLA, consist of heterogeneous microstructural compartments including crystal domains, where molecules are differentially aligned and packed, and amorphous regions where they are randomly oriented.…”

Research into biodegradable polymeric stents: a review of experimental and modelling work

“…Inflation rate affected stent expansion mainly during inflation process, while not much difference was shown after balloon deflation. Wang et al [36] studied the mechanical deformation of a PLLA biodegradable coronary stent using experimental and computational methods. They modelled the crimping of stent to an outer diameter of 1.41 mm and subsequent expansion to different inner diameters.…”