Anatomical Feasibility of an Off-the-shelf Scalloped Stent-graft for Infrarenal Abdominal Aneurysm With a Hostile Neck (ReSTHoNe Study)
Conditions: Aortic Aneurysm
Sponsor: Azienda Ospedaliero-Universitaria di Modena

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TITLE 
Anatomical feasibility of an off-the-shelf scalloped stent-graft for 
infrarenal abdominal aneurysm with a hostile neck (ReSTHoNe 
study) 
PARTECIPATING 
CENTERS 
AND 
INVESTIGATORS 
Coordinator centre: AOU di Modena,  Main investigator Prof. 
Roberto Silingardi (UNIMORE). Other investigators: Stefano Gennai, 
MD (AOU),  Giuseppe Saitta, MD (AOU), Francesco Andreoli, MD 
(UNIBO), Mattia Migliari, MD (UNIBO), Francesca Rossi, MD 
(UNIBO) and Nicola Leone, MD (UNIBO).  
 
RATIONAL 
Endovascular aneurysm repair (EVAR) is currently accepted as the 
preferred choice to treat the abdominal aortic aneurysms (AAA) 
with a feasible anatomy1,2.  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 anatomy6.  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 arteries7.  Some aortic neck characteristics contribute in 
the definition of ‘‘hostile neck,’’ particularly length shorter than 15 

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mm and angulation among others8. 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 mortality9. 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 feasible9.  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 creating 
the ideal condition for EVAR failure9. 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)10. 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 (Treovance, Terumo 
Aortic) to treat infrarenal AAA with a short and/or angulated neck.  
Schedule 
Step 1: Ex-Vivo phase  
- 
Step 1.0: Protocol proposal and CE approval 
- 
Step 1.1: CTA measurement 
- 
Step 1.2: CTA data analysis 
- 
Step 1.3: Models fitness evaluation  

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- 
Step 1.4: Preliminary publication and endograft production 
 
STUDY DESIGN 
Step 1-Single center retrospective observational study on the 
anatomical applicability in the coordinator center of an off-the-shelf 
scalloped device to treat infrarenal AAA with short and/or 
angulated neck. 
 
EX VIVO AND IN VIVO 
TREATMENT 
Step 1: 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. Preoperative contrast-enhanced computed 
tomography scans (CTAs) were independently reviewed by 2 
vascular surgeons (investigators) experienced in the planning of 
aortic procedures using a dedicated workstation with dedicated 
vascular software (EndoSize, Thereva). Multiplanar and curved 
reconstructions of each CTA were used to assess the required 
measurements. In addition to standard measurement taken to 
plan an EVAR procedure the center-lumen-line distance from the 
inferior margin of the upper renal artery to the inferior margin of 
the lower renal artery was taken in order to estimate the gain of 
neck length permitted with the scallop. An inter-examiner or intra-
examiner error of 5% was accepted. In case of a variation >5%, a 
third investigator of the study would in- dependently reanalyze 
the CTA.  To study the suitability of the device, 2 different 
endograft models were constructed and fitted in the CTA-based 

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measurements made as described to evaluate the anatomical 
feasibility of these models.  
INCLUSION CRITERIA 
Step 1: 
- Patients Electively treated with EVAR or AAA at the coordinator 
center 
- Age >18  
-Both sex 
-Preoperative 2.5mm CTA available  
-Written informed consent. 
SAMPLE SIZE 
Step 1: No statistical analysis of the sample size was carried 
out. Considering the number of AAA treated in the 
coordinator center each year and analyzing a time interval 
of 10 years a sample size of 1000 CTA was estimated. This 
number should be sufficient to carry out the anatomical 
feasibility analysis. 
 
OUTCOMES/ENDPOINTS Step 1  
Outcome: Anatomical feasibility evaluation  
 
STATISTICAL ANALYSIS 
To study the suitability, 2 different endograft designs were 
constructed. The preoperative measurements were made 
according to a previously described methodology. The models 
were matched with each preoperative CTA measure in order to 
evaluate if they fit or not in the index patients. Continuous 
variables are expressed as mean, and standard deviation and 

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differences were tested with the two-sided t-test or the Mann–
Whitney U-test, if appropriate. Categorical variables are expressed 
as counts and percentages and the chi-square test or Fisher’s exact 
test was used for analysis. All data were entered into the logistic 
regression model if they had a univariable P-value of <0.05. Data 
resulted significative in this model were put in a multivariate one. 
In the multivariable analyses, clinical factors or potential 
confounding variables were expressed as odds ratio with 95% 
confidence interval (CI). The goodness of fit of the logistic 
regression models has been assessed calculating the C-statistic.. 
The analysis was carried out using STATA 14.  
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