Modeling and computational analysis of the hemodynamic effects of crossing the limbs in an aortic endograft ("ballerina" position)

Abstract

Purpose: To evaluate the displacement forces acting on an aortic endograft when the iliac limbs are crossed ("ballerina" position). Methods: An endograft model was computationally reconstructed based on data from a patient whose infrarenal aortic aneurysm had an endovascular stent-graft implanted with the iliac limbs crossed. Computational fluid dynamics analysis determined the maximum displacement force on the endograft and separately on the bifurcation and iliac limbs. Its analogue model was reconstructed for comparison, assuming the neck, main body, and total length constant but considering the iliac limbs to be deployed in the usual bifurcated mode. Calculations were repeated after developing "idealized" models of both the bifurcated and crossed-limbs endografts with straight main bodies and no neck angulation or curved iliac segments. Results: The vector of the total force was directed anterocaudal for both the typical bifurcated and the crossed-limbs configurations, with the forces in the latter slightly reduced and the vertical component accounting for most of the force in both configurations. Idealized crossed-limbs and bifurcated configurations differed only in the force on the iliac limbs, but this difference disappeared in the realistic models. Conclusion: Crossing of the iliac limbs can slightly affect the direction of the displacement forces. Although this configuration can exert larger forces on the limbs than in the bifurcated mode, this effect can be blunted by concomitant modifications in the geometry of the main body and other parts of the endograft, making its hemodynamic behavior resemble that of a typically positioned endograft. © 2012 by the International Society of Endovascular Specialists.