Forty-two noninfected femoral anastomotic aneurysms that occurred after aortobifemoral bypass were repaired during a 7 year period. Twenty of these were recurrent aneurysms. In an attempt to define the cause of recurrence, a number of factors were studied including infection, suture failure, graft deterioration, defective graft manufacture, graft dilatation, and arterial degeneration. Five grafts in the primary group failed because of inherent defects in the graft structure. Two lightweight Dacron grafts showed generalized graft dilatation, and three unwrapped expanded polytetrafluoroethylene grafts had linear tears at the anastomosis. We believe that such graft degeneration does not represent a current problem because the polytetrafluoroethylene grafts now used are reinforced, and lightweight Dacron grafts are no longer made. Two primary femoral anastomotic aneurysms resulted from broken polypropylene suture. No infections were found in the primary or recurrent groups of aneurysms. Arterial degeneration adjacent to the anastomosis, consisting of a decrease in wall thickness due to loss of smooth muscle with proliferation of elastic fibers and disruption of elastic laminae, was a consistent finding in the remaining 15 primary femoral anastomotic aneurysms and all recurrent femoral anastomotic aneurysms. In many instances of primary femoral anastomotic aneurysm and in all instances of recurrent aneurysms dilatation of the Dacron graft with secondary arterial degeneration was believed to be the cause of aneurysm formation. Graft dilatation without fiber deterioration is an inherent problem in Dacron grafts and reportedly varies from 10 to 50 percent of the original graft diameter. This dilatation plus the use of initial graft diameters larger than the host artery leads to increased tension at the anastomotic site with subsequent arterial degeneration. For the aforementioned reasons, our current practice and recommendation is that repair of all anastomotic aneurysms be with expanded polytetrafluoroethylene grafts sized to approximate the host artery since its dilatation at sites of arterial pressure is minimal.
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