Purpose: The structure of infrarenal aortic aneurysm was studied as a basis for design of a transfemoral system of aneurysm repair. This information was particularly important because endovascular techniques, unlike conventional techniques, afford little opportunity for intraoperative adjustments. Methods: Three-dimensional computer reconstructions of the distal aorta, the renal arteries, the aneurysm and the iliac arteries were generated from computed tomography scanning data in 22 patients with aortic aneurysms. Results: The proximal neck of the aneurysm was longer than 20 mm in 14 patients, and the mean length (of all 22) was 26.7 +/- 4.1 mm. In contrast, only one patient had a distal cuff longer than 20 mm and 14 of the others had no measurable distal cuff. The mean distal cuff length (of all 22) was 4.2 +/- 1.6 mm. There was no significant difference between mean aneurysm diameter in the anteroposterior direction (58.0 +/- 3.2 mm) and the transverse direction (56.4 +/- 3.3 mm), although corresponding values in individual patients were often different. Aneurysm diameter correlated with aneurysm length (r = 0.79, p < 0.001). The proximal right common iliac artery deviated from the axis of the distal aorta by 40.0 +/- 5.8 degrees, whereas the left deviated by 47.8 +/- 5.4 degrees. One of the iliac arteries deviated by more than 45 degrees in 12 cases. Eleven common iliac arteries in seven patients were aneurysmal. Fifteen patients had no aneurysm of the common iliac arteries, and another three had segments of nondilated common iliac artery distal to iliac aneurysms on both sides. Conclusions: Computerized three-dimensional reconstruction facilitated interpretation of anatomic information from computed tomography scans, particularly the length of the aneurysm neck and shape of the iliac arteries. On the basis of this information, we expect that few patients will have too short an aneurysm neck for endovascular aneurysm repair, but many will require a bifurcated graft for secure, hemostatic implantation distally.
