Abstract: Long-term durability of EVAR is impaired by aortic neck dilatation (AND) that is associated with late Type 1 endoleak, migration and aneurysm rupture. Current endografts employ radial force, barbs and columnar rigidity for fixation. Metal helical endostaples provide longitudinal fixation and radial fixation to resist vascular dilatation. AND greater >15 % is reported in a range of 21%-28% at 2 years in the three largest studies. We analyzed the core lab imaging data from the Phase II IDE STAPLE-2 trial to evaluate the effect of helical endostaple fixation on AND