Development of an Automated Measure of Iliac Artery Tortuosity that Successfully Predicts Early Graft-Related Complications Associated with Endovascular Aneurysm Repair

ObjectivesIliac artery tortuosity has been linked to the likelihood of complications following endovascular aneurysm repair (EVAR). Measures of tortuosity can be established from CT images; however, the reproducibility of existing scoring techniques has not been clearly established. It remains unclear whether it is tortuosity at focal locations or for the vessel as a whole that is most relevant to adverse events. The two aims of this study were to develop an automated measure of iliac artery tortuosity to assist with surgical planning by providing an objective assessment of procedural difficulty, and to correlate this measure with early postoperative outcomes.Design and methodsUnlike existing approaches, the present measure of tortuosity considers spatial scale, which incorporates the effects of local anatomy. A computerized imaging algorithm was used to segment vasculature and establish a medial line and vascular boundary from contrast enhanced CT scans of 150 patients undergoing EVAR. Two tortuosity measures were examined: curvature and vessel to straight-line length (L1/L2-ratio). For a given spatial scale, the maximum tortuosity was computed on both iliac arteries and the artery with the lower maximum was selected for analysis. Correlation of tortuosity with early (<30 day) and longer-term graft-related complications was assessed.ResultsMaximal tortuosity at a 10 mm scale was a significant predictor of early (<30 day) complications (p = .016 for curvature and p = .006 for L1/L2-ratio), but not of long-term complications. Aneurysmal diameter was independent of tortuosity (Pearson's r value = −.006).ConclusionThe results demonstrate that, at a local scale, tortuosity measures are correlated with early outcomes. The spatial scale at which tortuosity is measured is important. The optimal scale of 10 mm implies that adverse events could be linked to a focal anatomical location.