A Finite Element Analysis Rupture Index (FEARI) as an Additional Tool for Abdominal Aortic Aneurysm Rupture Prediction

Abstract

Currently, abdominal aortic aneurysms (AAAs), which are a permanent dilation of the aorta, are treated surgi- cally when the maximum transverse diameter surpasses 5.5cm. AAA rupture occurs when the locally acting wall stress exceeds the locally acting wall strength. There is a need to review the current diameter-based criterion, and so it may be clinically useful to develop an additional tool to aid the surgical decision-making process. A Finite Element Analysis Rup- ture Index (FEARI) was developed. Ten patient-specific AAAs were reconstructed, and the corresponding wall stress computed. Previous experimental work on determination of ultimate tensile strengths (UTS) from AAA tissue samples was implemented in this study. By com- bining peak wall stress along with average regional UTS, a new approach to the estimation of patient-specific rupture risk has been developed. Ten cases were studied, all of which were awaiting or had previously undergone surgical AAA repair. A detailed exami- nation of these ten cases utilising the FEARI analysis suggested that there was a possibility that some of the AAAs may have been less prone to rupture than previously considered. It is proposed that FEARI, used alongside other rupture risk factors, may improve the current surgical decision-making process. The use of FEARI as an additional tool for rupture prediction may provide a useful adjunct to the diameter-based approach in surgical decision-making.