title: A computational study of the magnitude and direction of migration forces in patient-specific abdominal aortic aneurysm stent-grafts.
abstract: OBJECTIVE
  Endovascular aneurysm repair for abdominal aortic aneurysm (AAA) is now a widely adopted treatment. Several complications remain to be fully resolved and perhaps the most significant of these is graft migration. Haemodynamic drag forces are believed to be partly responsible for migration of the device. The objective of this work was to investigate the drag forces in patient-specific AAA stent-grafts.
  
  
  METHODS
  CT scan data was obtained from 10 post-operative AAA patients treated with stent-grafts. 3D models of the aneurysm, intraluminal thrombus and stent-graft were created. The drag forces were determined by fluid-structure interaction simulations. A worst case scenario was investigated by altering the aortic waveforms.
  
  
  RESULTS
  The median resultant drag force was 5.46 N (range: 2.53-10.84). An increase in proximal neck angulation resulted in an increase in the resultant drag force (p = 0.009). The primary force vector was found to act in an anterior caudal direction for most patients. The worst case scenario simulation resulted in a greatest drag force of 16 N.
  
  
  CONCLUSIONS
  Numerical methods can be used to determine patient-specific drag forces which may help determine the likelihood of stent-graft migration. Anterior-posterior neck angulation appears to be the greatest determinant of drag force magnitude. Graft dislodgement may occur anteriorally as well as caudally.
authors.affiliation: Centre for Applied Biomedical Engineering Research, Department of Mechanical and Aeronautical Engineering and Materials and Surface Science Institute, University of Limerick, Ireland.
authors.forename: D S
authors.initials: DS
authors.lastname: Molony
authors.forename: E G
authors.initials: EG
authors.lastname: Kavanagh
authors.forename: P
authors.initials: P
authors.lastname: Madhavan
authors.forename: M T
authors.initials: MT
authors.lastname: Walsh
authors.forename: T M
authors.initials: TM
authors.lastname: McGloughlin
mesh_terms: D001012:Aorta, Abdominal / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D001027:Aortography / Q000379:methods; D001696:Biomechanical Phenomena; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects / Q000295:instrumentation*; D003198:Computer Simulation; D005548:Foreign-Body Migration / Q000209:etiology* / Q000503:physiopathology; D006439:Hemodynamics; D006801:Humans; D008955:Models, Cardiovascular; D015233:Models, Statistical; D009716:Numerical Analysis, Computer-Assisted; D011474:Prosthesis Design; D015607:Stents; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome