Investigation of the Observed Rupture Lines in Abdominal Aortic Aneurysms Using Crack Propagation Simulations

Abstract

The objective of the study is to use crack propagation simulation to study the rupture site characteristics in ruptured abdominal aortic aneurysms (AAA). In a study population of four ruptured AAA harvested whole from cadavers, the rupture lines were precisely documented. The wall properties such as thickness and material parameters were experimentally determined. Using subject-specific three-dimensional (3D) geometry and a finite elastic isotropic material model with subject-specific parameters, crack propagation simulations were conducted based on basic fracture mechanics principles to investigate if and how localized weak spots may have led to the rupture lines observed upon harvest of ruptured AAA. When an initial crack was imposed at the site of peak wall stress, the propagated path did not match the observed rupture line. This indicates that in this study population, the peak wall stress was unlikely to have caused the observed rupture. When cracks were initiated at random locations in the AAA along random orientations and for random initial lengths, the orientation of the resulting propagated rupture line was always longitudinal. This suggests that the AAA morphology predisposes the AAA to rupture longitudinally, which is consistent with observations. And finally, it was found that, in this study population, rupture may have initiated at short segments of less than 1 cm length that then propagated to the observed rupture lines. This finding provides some guidance for the spatial resolution (approx. 1 cm) of weak spots to investigate for in AAA during ex vivo experimental and in vivo elastography studies. The small study population and lack of a reliable failure model for AAA tissue make these findings preliminary.