title: A novel method to estimate iliac tortuosity in evaluating EVAR access.
abstract: OBJECTIVE
  To subjectively and objectively evaluate the methods used for preoperative assessment of iliac artery tortuosity in patients with abdominal aortic aneurysms (AAA).
  
  
  METHODS
  Iliac artery tortuosity was assessed retrospectively in 188 patients (160 men; mean age 73 years) diagnosed with AAA at our clinic in 2006 and 2007. All patients underwent preoperative computed tomography (CT) with predominantly thin-slice acquisitions. CT data were analyzed in a dedicated 3-dimensional workstation to perform centerline-of-flow measurements on 376 iliac arteries. Iliac tortuosity was evaluated using the following methods: (1) subjective grading (none, mild, moderate, severe) by 2 experienced observers, (2) calculating the modified iliac tortuosity index based on the published reporting standards for endovascular aneurysm repair, and (3) using the shortest distance between the aortic bifurcation and the common femoral artery (CFA) on axial CT scans as a surrogate for the tortuosity index. Correlation between the objective methods was assessed, and all 3 methods were evaluated for intra- and interobserver agreement.
  
  
  RESULTS
  (1) The intra- and interobserver agreement was substantial (κ = 0.71 and κ = 0.65, respectively) for subjective grading, but few variations were found in the calculated tortuosity indexes between the subjective groups. (2) Intra- and interobserver correlations when measuring the iliac tortuosity index were strong (r = 0.94 and r = 0.79, respectively), with good intra- and interobserver agreement. (3) The new method had a strong correlation with iliac tortuosity index (r = 0.78); segregating the iliac arteries into 3 length categories (<10 cm, 10-15 cm, >15 cm), the mean iliac tortuosity indexes were 2.0 ± 0.37, 1.6 ± 0.21, and 1.1 ± 0.27, respectively (p<0.001). This strong correlation was not seen when measuring the iliac artery length in CLF reconstruction (r = 0.31), proving little variation in CLF length among patients.
  
  
  CONCLUSIONS
  Subjective grading of iliac artery tortuosity had substantial agreement between investigators but cannot be recommended as a surrogate for the tortuosity index in access evaluation. The iliac artery tortuosity index is most accurate, but complex and time-consuming. As the CLF length varies only slightly among patients, the new method using the shortest aortic bifurcation-CFA distance on an axial CT scan is a good substitute for the iliac tortuosity index and can often replace it clinically.
authors.affiliation: Vascular Center, Skåne University Hospital, Malmö, Sweden. thorark@hotmail.com
authors.forename: Thorarinn
authors.initials: T
authors.lastname: Kristmundsson
authors.forename: Björn
authors.initials: B
authors.lastname: Sonesson
authors.forename: Timothy
authors.initials: T
authors.lastname: Resch
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging* / Q000601:surgery; D001027:Aortography / Q000379:methods*; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation / Q000295:instrumentation; D057510:Endovascular Procedures / Q000295:instrumentation; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007083:Iliac Artery / Q000000981:diagnostic imaging* / Q000601:surgery; D021621:Imaging, Three-Dimensional; D008297:Male; D061330:Multidetector Computed Tomography; D015588:Observer Variation; D018579:Patient Selection; D011237:Predictive Value of Tests; D011300:Preoperative Care; D011474:Prosthesis Design; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D012189:Retrospective Studies; D015607:Stents; D013548:Sweden