Comparison of the fixation strength of standard and fenestrated Stent-Grafts for endovascular abdominal aortic aneurysm repair

Purpose: To determine whether fenestrated stent-grafts provide better stability to resist migration than standard non-fenestrated stent-grafts. Methods: Truncated fenestrated stent-grafts with a single fenestration were deployed in bovine aortic segments with a side branch. Balloon-expandable stents were then delivered into the branches. Similarly, standard stent-grafts of the same dimensions were deployed for comparison. The aorta was pressurized to achieve stent-graft oversizing of 5%, 10%, or 20%. The force required to cause distal migration was recorded by a digital force gauge attached to the stent-graft. Results: Displacement of the stent-grafts occurred in 2 distinct phases: an initial yield during which the barbs embedded in the aortic wall and a final displacement leading to significant migration and dislodgement of the device. The displacement force that initiated each phase was dependent upon the degree of oversizing of the stent-graft relative to the aortic diameter. For 5%, 10%, and 20% oversizing, the mean displacement forces in the initial displacement phase were 3.39 +/- 0.37, 4.32 +/- 0.63, and 7.69 +/- l.18 N, respectively, in non-fenestrated grafts and 10.48 +/- 1.23, 11.45 +/- 1.48, 12.12 +/- 1.42 N in fenestrated grafts. The displacement forces in the final displacement phase were 8.10 +/- 0.92, 10.76 +/- 1.74, and 16.82 +/- 0.92 N for non-fenestrated and 22.56 +/- 1.60, 28.24 +/- 1.56, and 33.01 +/- 1.75 N for fenestrated stent-grafts. The differences in displacement forces between standard and fenestrated stent-grafts were significant for both phases (p<0.001) at all oversizing levels. Conclusion: Improvement in fixation strength was noted with increasing stent-graft oversizing of up to 20%. Fenestrated stent-grafts offer higher ultimate fixation compared to standard devices. However, the ultimate fixation strength was not recruited until an initial phase of short migration occurred as the barbs engaged. While this movement is inconsequential with standard stent-grafts, it has the potential to crush the stents placed into aortic side branches with fenestrated endografts.