Micromovements at the aortic aneurysm neck measured during open surgery with close-range photogrammetry: Implications for aortic endografts

Purpose: To describe the motion of abdominal aortic aneurysm (AAA) as a fir st step toward determining if stent-graft migration may be due to propulsiv e movements at the neck. Method. In an initial laboratory validation test, a silicone AAA model was imaged with a stereo-pair configuration of calibrated digital cameras using retro-reflective and ink dot surface targets. This technique was then appl ied to 4 aneurysm necks imaged at open surgery. In each case the paired ima ges were measured and analyzed to produce sequences of accurate three-dimen sional (3-D) surface models of the anterior aspect of the aortic neck. Engi neering techniques were used to visualize and identify differences between the generated surfaces, allowing changes in shape of the aortic wall to be determined. Results: The correlation between stereoscopic digital imaging with electron ic caliper measurements of linear dimensions was accurate, irrespective of the type of surface targets used (r(2) = 0.98). The AAA neck demonstrated c omplex 3-D movements that ranged from 1.0 to 1.5 mm in the radial direction to 0.6 to 1.0 mm along the longitudinal axis, with a 0.44 to 0.59-mm rotat ional component (p < 0.05). Conclusions: This pilot study raises questions about the validity of accept ed models of arterial wall movements and compliance in which rotation has n ot been described. The technique used to measure dynamic neck morphology ap pears promising as a means to further define the mechanical parameters of t he human aorta, which may assist in designing stent-grafts.