In clinical practice a lot of EVAR cases are performed IFU for adverse neck anatomy(6) with acceptable short- and mid-term outcomes, but the long-term durability is currently an issue (7). Neck length shorter than 15 mm and angulation are two of. neck charteristics. that contribute more to define an "hostile neck" (8). The issue linked to the anatomical not feasibility of standard EVAR in patients not eligible for OR can be solved with custom made devices (CMD), but they were limited by high production costs and long time for creations (10-12 weeks)1. Nowadays no one off-the-shelf device aimed to overcome neck hostility in AAA is available on the market.

The present study aims at evaluating the anatomical applicability of an off-the-shelf scalloped stent-graft to treat infrarenal AAA with a short and/or angulated neck.

Endovascular aneurysm repair (EVAR) is currently accepted as the preferred choice to treat abdominal aortic aneurysms (AAA) with feasible anatomy. Although approximately 40-60% of AAA patients are not considered anatomically feasible for EVAR, mainly in reason of a "hostile neck anatomy". In ''real-world'' clinical practice, up to 44% of EVAR cases are performed outside Instruction For Use (IFU) for adverse neck anatomy. The off-label use of standard EVAR is currently used for patients who are not eligible for OR, with acceptable short- and mid-term outcomes, Endovascular aneurysm repair (EVAR) is currently accepted as the preferred choice to treat the abdominal aortic aneurysms (AAA) with feasible anatomy. Although approximately 40-60% of AAA patients are not considered anatomically feasible for EVAR, mainly in reason of a "hostile neck anatomy"3-5. In ''real-world'' clinical practice, up to 44% of EVAR cases are performed outside Instruction For Use (IFU) for adverse neck anatomy. The off-label use of standard EVAR is currently used for patients who are not eligible for OR, with acceptable short- and mid-term outcomes, but the long-term durability of EVAR depends on the maintenance of the seal between the endograft and the aortic neck as well as the iliac arteries. Some aortic neck characteristics contribute to the definition of ''hostile neck,'' particularly length shorter than 15 mm and angulation among others. From a recent Consensus Conference, the influence of each characteristic on early or late EVAR failure is not clear, but hostile neck morphology is generally associated with higher rates of aneurysm-related adverse events and mortality. A recent independent Expert Panel, applying the Delphi methodology Indeed, agreed to define 10 mm as the threshold value below which standard EVAR should not be considered feasible. Moreover, the same experts agreed on the fact that an angulation above 60° is considered a hostile criterion for EVAR procedure. Finally should be considered that some "hostility" factors can be present at the same time and create the ideal condition for EVAR failure. The issue linked to the anatomical not the feasibility of standard EVAR in patients not eligible for OR can be solved with custom made devices (CMD), but they were limited by high production costs and long time for creations (10-12 weeks)1. Nowadays no one off-the-shelf device aimed to overcome neck hostility in AAA is available on the market.

The present study aims at evaluating the anatomical applicability of an off-the-shelf scalloped stent graft to treat infrarenal AAA with a short and/or angulated neck. From an informal review of some CTA of patients treated with EVAR or OR in mentioned unit, the authors found that more the 20% presented a distance between the two renal arteries more than 5mm. The idea of an "off-the-shelf" graft with a single scallop theoretically had to permit to gain some length along the aortic neck. Furthermore also in the case of angulation, a single scallop theoretically reduced the risk of bird beck and gutter. The aim of the study is to evaluate if a single scalloped "off-the-shelf" stent graft could be appliable and feasible in an adequate number of patients.

Inclusion Criteria:

• Patients Electively treated with EVAR or AAA at the coordinator center
• Age >18
• Both sex
• Preoperative 2.5mm CTA available
• Written informed consent.

Exclusion Criteria:

• All. patients not fulfilling the inclusion criteria

All patients affected by AAAs and electively treated with EVAR or OR in the Vascular Surgery Unit of Modena e Reggio Emilia from 2010 to 2020 were considered eligible for the ex-vivo feasibility study. Mandatory condittion for tthhe enrollemnt is an available 2.5mm CTA.