Further Roles of Geometry and Properties in the Mechanics of Saccular Aneurysms

Rupture of intracranial saccular aneurysms continues to result in significant morbidity and mortality. Although it has long been thought that biomechanical factors play key roles in the genesis, growth, and rupture of these lesions, few analysis have employed realistic descriptions of the geometries and material properties. This paper presents parametric finite element studies for subclasses of elliptical and spherical lesions which complement those recently reported by Kyriacou and Humphrey. In particular, we show again that lesion shape, not size, is a primary determinant of aneurysmal wall stress. Moreover, material anisotropy and geometry can exhibit competing or synergistic effects on the stress fields - this suggests that these interactions may be important in the formulation of theories on lesion growth. Finally, we show that Laplace's equation (for spherical membranes) yields reasonable approximations for wall stress only for a very limited class of lesions. There is a need, therefore, for detailed analysis and thus more precise data on lesion geometry, material properties, and loading conditions.