Frame dislocation of body middle rings in endovascular stent tube grafts

Objectives: to understand the cause, and propose a mechanism for frame dislocation in endovascular grafts. Materials and methods:five tube grafts were explanted due to secondary distal leakage 15-21 months after operation. One bifurcated graft was removed during emergency operation after aortic rupture caused by secondary leakage. A second bifurcated graft was harvested from a patient with thrombotic occlusion of one limb, who died after transurethral prostatic resection. The inside of the grafts were examined endoscopically. The stent was inspected after removal of the fabric, broken ligatures were counted and examined by scanning electron microscopy. The fabric strength was tested by probe puncture. Results: we found 17-44% of the stent ligatures of the body middle rings to be loose. The knots were intact. Degradation of the polyester textile was not observed. Conclusions: continuous movements in the grafted aorta and blood pressure impose permanent stress to the stent frame and the polyester fabric resulting in morphological changes in the body middle ring of grafts. The clinical implications of the suture breakages are unknown although they may be related to distal secondary leakage in tube grafts.