Biomechanical Rupture Risk Assessment of Abdominal Aortic Aneurysms: Model Complexity versus Predictability of Finite Element Simulations

Objective: Investigation of the predictability of finite element (FE) models regarding rupture risk assessment of abdominal aortic aneurysms (AAAs). Materials and materials: Peak wall stress (PWS) and peak wall rupture risk (PWRR) of ruptured (n = 20) and non-ruptured (n = 30) AAAs were predicted by four FE models of different complexities derived from computed tomography (CT) data. Two matching sub-groups of ruptured and non-ruptured aneurysms were used to investigate the usability of different FE models to discriminate amongst them. Results: All FE models exhibited a strong positive correlation between PWS and PWRR with the maximum diameter. FE models, which excluded the intra-luminal thrombus (ILT) failed to discriminate between ruptured and non-ruptured aneurysms. The predictability of all applied FE models was strengthened by including wall strength data, that is, computing the PWRR. The most sophisticated FE model applied in this study predicted PWS and PWRR 1.17 (p = 0.021) and 1.43 (p = 0.016) times higher in ruptured than diameter-matched non-ruptured aneurysms, respectively. Conclusions: PWRR reinforces PWS as a biomechanical rupture risk index. The ILT has a major impact on AAA biomechanics and rupture risk, and hence, needs to be considered in meaningful FE simulations. The applied FE models, however, could not explain rupture in all analysed aneurysms. (C) 2010 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.