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

The rate of post-operative complications is the main drawback of endovascular repair, a technique used to treat abdominal aortic aneurysms. Complex anatomies, featuring short aortic necks and high vessel tortuosity for instance, have been proved likely prone to these complications. In this context, practitioners could benefit, at the preoperative planning stage, from a tool able to predict the post-operative position of the stent-graft, to validate their stent-graft sizing and anticipate potential complications. In consequence, the aim of this work is to prove the ability of a numerical simulation methodology to reproduce accurately the shapes of stent-grafts, with a challenging design, deployed inside tortuous aortic aneurysms. Stent-graft module samples were scanned by X-ray microtomography and subjected to mechanical tests to generate finite-element models. Two EVAR clinical cases were numerically reproduced by simulating stent-graft models deployment inside the tortuous arterial model generated from patient pre-operative scan. In the same manner, an in vitro stent-graft deployment in a rigid polymer phantom, generated by extracting the arterial geometry from the preoperative scan of a patient, was simulated to assess the influence of biomechanical environment unknowns in the in vivo case. Results were validated by comparing stent positions on simulations and post-operative scans. In all cases, simulation predicted stents deployed locations and shapes with an accuracy of a few millimetres. The good results obtained in the in vitro case validated the ability of the methodology to simulate stent-graft deployment in very tortuous arteries and led to think proper modelling of biomechanical environment could reduce the few local discrepancies found in the in vivo case. In conclusion, this study proved that our methodology can achieve accurate simulation of stent-graft deployed shape even in tortuous patient specific aortic aneurysms and may be potentially helpful to help practitioners plan their intervention.

[1]  D. Nash,et al.  On the experimental testing of fine Nitinol wires for medical devices. , 2011, Journal of the mechanical behavior of biomedical materials.

[2]  P Segers,et al.  Filling the void: a coalescent numerical and experimental technique to determine aortic stent graft mechanics. , 2013, Journal of biomechanics.

[3]  Rangasami L. Kashyap,et al.  Building Skeleton Models via 3-D Medial Surface/Axis Thinning Algorithms , 1994, CVGIP Graph. Model. Image Process..

[4]  C. Kleinstreuer,et al.  Computational mechanics of Nitinol stent grafts. , 2008, Journal of biomechanics.

[5]  Mark F Fillinger,et al.  Prediction of rupture risk in abdominal aortic aneurysm during observation: wall stress versus diameter. , 2003, Journal of vascular surgery.

[6]  Sandra J Shefelbine,et al.  BoneJ: Free and extensible bone image analysis in ImageJ. , 2010, Bone.

[7]  Xiao Yun Xu,et al.  Patient-specific analysis of displacement forces acting on fenestrated stent grafts for endovascular aneurysm repair. , 2014, Journal of biomechanics.

[8]  Pierre Badel,et al.  Patient-specific numerical simulation of stent-graft deployment: Validation on three clinical cases. , 2015, Journal of biomechanics.

[9]  P Haigron,et al.  Estimation of clinically relevant indicators for EVAR using patient-specific finite element simulation , 2015, Computer methods in biomechanics and biomedical engineering.

[10]  Alessandro Reali,et al.  Patient-specific aortic endografting simulation: From diagnosis to prediction , 2013, Comput. Biol. Medicine.

[12]  R J Hinchliffe,et al.  Endovascular repair of abdominal aortic aneurysms in patients with severe angulation of the proximal neck using a flexible stent-graft: European Multicenter Experience. , 2006, The Journal of cardiovascular surgery.

[13]  F. Vermassen,et al.  What if you stretch the IFU? A mechanical insight into stent graft Instructions For Use in angulated proximal aneurysm necks. , 2014, Medical engineering & physics.

[14]  Marco Viceconti,et al.  Evaluation of the generality and accuracy of a new mesh morphing procedure for the human femur. , 2011, Medical engineering & physics.

[15]  Pierre Badel,et al.  Finite Element Analysis of the Mechanical Performances of 8 Marketed Aortic Stent-Grafts , 2013, Journal of endovascular therapy : an official journal of the International Society of Endovascular Specialists.

[16]  A. AbuRahma,et al.  Clinical outcomes for hostile versus favorable aortic neck anatomy in endovascular aortic aneurysm repair using modular devices. , 2010, Journal of vascular surgery.

[17]  Garrett J. Hall,et al.  Comparison of element technologies for modeling stent expansion. , 2006, Journal of biomechanical engineering.

[18]  Tips and tricks for characterizing shape memory alloy wire: Part 3-localization and propagation phenomena , 2009 .

[19]  P. Desgranges,et al.  Limb graft occlusion following EVAR: clinical pattern, outcomes and predictive factors of occurrence. , 2007, European journal of vascular and endovascular surgery : the official journal of the European Society for Vascular Surgery.

[20]  P Segers,et al.  Virtual evaluation of stent graft deployment: a validated modeling and simulation study. , 2012, Journal of the mechanical behavior of biomedical materials.

[21]  Pierre Badel,et al.  Deployment of stent grafts in curved aneurysmal arteries: toward a predictive numerical tool , 2015, International journal for numerical methods in biomedical engineering.

[22]  Pierre Badel,et al.  Severe Bending of Two Aortic Stent-Grafts: An Experimental and Numerical Mechanical Analysis , 2012, Annals of Biomedical Engineering.

[23]  C. Kleinstreuera,et al.  Computational mechanics of Nitinol stent grafts , 2008 .

[24]  Nan Xiao,et al.  A computational framework for investigating the positional stability of aortic endografts , 2012, Biomechanics and Modeling in Mechanobiology.

[25]  S. Money,et al.  Aortic neck angulation predicts adverse outcome with endovascular abdominal aortic aneurysm repair. , 2002, Journal of vascular surgery.

[26]  J. Byrne,et al.  Prognosis of patients turned down for conventional abdominal aortic aneurysm repair in the endovascular and sonographic era: Szilagyi revisited? , 2001, Journal of vascular surgery.

[27]  Mark J Sculpher,et al.  Endovascular versus Open Repair of Abdominal Aortic Aneurysm , 2011 .

[28]  R. Ogden,et al.  Hyperelastic modelling of arterial layers with distributed collagen fibre orientations , 2006, Journal of The Royal Society Interface.

[29]  Pierre Badel,et al.  Computational comparison of the bending behavior of aortic stent-grafts. , 2012, Journal of the mechanical behavior of biomedical materials.