Computational comparison of the bending behavior of aortic stent-grafts

Abstract

Secondary interventions after endovascular repair of abdominal aortic aneurysms are frequent because stent-graft (SG) related complications may occur (mainly endoleak and SG thrombosis). Complications have been related to insufficient SG flexibility, especially when devices are deployed in tortuous arteries. Little is known on the relationship between SG design and flexibility. Therefore, the aim of this study was to simulate numerically the bending of two manufactured SGs (Aorfix--Lombard Medical (A) and Zenith--Cook Medical Europe (Z)) using finite element analysis (FEA). Global SG behavior was studied by assessing stent spacing variation and cross-section deformation. Four criteria were defined to compare flexibility of SGs: maximal luminal reduction rate, torque required for bending, maximal membrane strains in graft and maximal Von Mises stress in stents. For angulation greater than 60°, values of these four criteria were lower with A-SG, compared to Z-SG. In conclusion, A-SG was more flexible than Z-SG according to FEA. A-SG may decrease the incidence of complications in the setting of tortuous aorto-iliac aneurysms. Our numerical model could be used to assess flexibility of further manufactured as well as newly designed SGs.

Virtual evaluation of stent graft deployment: A validated modeling and simulation study

“…This can happen due to kinks or thrombosis as a late event. A recent study by Demanget et al (2012) simulated simple bending of stent graft iliac legs, showing that stent design can greatly influence bending behavior. Thrombosis may be caused by unfavorable flow alterations.…”

Patient-specific simulation of endovascular repair surgery with tortuous aneurysms requiring flexible stent-grafts

“…The textile was modelled as a linear elastic orthotropic material. Its constitutive parameters and thickness (Table 5) were determined after in-house experimental tests, to match experimental in-plane and bending stiffness reported in (Demanget et al, 2012a).…”

Initial Single-Center Experience with the Ovation Stent-Graft System in the Treatment of Abdominal Aortic Aneurysms: Application to Challenging Iliac Access Anatomies

“…Gandini et al 12 reported a case of successful use of the Ovation stent graft in a challenging case of aortoiliac anatomy combining a narrow (14 mm) calcified bifurcation with a calcified, narrow iliac 21 The combination of these features enhances the flexibility of the iliac limbs and may attribute to the optimal clinical performance of Ovation to confront challenging iliac anatomies, providing better stent interlocking during bending and, thus, lower luminal reduction. 22,23 Therefore, although the IFU of the particular endograft suggest an inner iliac wall diameter of 8 mm, the reported results in the literature advocate the use in much smaller diameters. The lack of nitinol support from the main body and iliac limb gates may render the contralateral iliac limb of the endograft prone to compromisation or collapse against the AAA sac wall in cases of a tight endoluminal space due to narrow aortoiliac bifurcation and eccentric intraluminal thrombus, complicating its catheterization and increasing the intraprocedural difficulties.…”