Finite element modelling of stented aorta as a hyperelastic material

In recent years stent-grafting has become more popular in treating abdominal aortic aneurysms (AAA) due to its less-invasive nature. However there are still problems such as endoleaks (e.g. endoleak through branches or porous graft material) and from neck dilation causing late migration. Understanding this latter effect is the basis for the current study. We hypothesized that excessive stent force leads to arterial remodelling thus contributing to aneurysmal neck dilation and endoleak. The aim of this study is to estimate the stress concentration within the aorta using finite element analysis (FEA) to simulate stent expansion into the arterial wall. In order to build an appropriate arterial wall model, the mechanical properties of the artery were determined under appropriate test conditions. Results showed a hyperelastic model to be a better choice than a linear elastic one with simulation results corresponding well with the experimental data (less than 2% deviation within the mean blood pressure range: 80-120mmHg). Stent contact simulation with a hyperelastic-characterized artery has demonstrated a maximum localised stress concentration at the apices of a zig-zag stent structure contact, the stresses being 3 similar to 5 times the level predicted for the straight section and 20 similar to 50 times of the controlled non-stented artery.