**7. False anastomotic aneurysms (FAA)**

Most common false aneurysm belongs to group of anastomotic aneurysms and they present clinical challenges in detection, evaluation, and treatment. The incidence is approximately between 1.4% and 4% [44]. Claytor and associates, in 1956, reported the first case of anastomotic aneurysm in a patient after prosthetic aortic graft placement [45].

In 1978, Wesolowski outlined these common causes of FAA [46]:


Although silk was used as a suture material for anastomosis (prior to 1967), the most frequent cause of FAA was breaking of the suture material [47-54]. Introduction of synthetic polyfilament suture materials has significantly decreased this cause. Also, the prosthesis defects in manufacture have long ceased to be the cause of the FAA. A whole range of arterial wall changes could lead to the formation of an FAA: infection arterial degeneration, aseptic necrosis of the suture line, extensive endarterectomy, and large ''patch'' or anastomosis, according to the Laplace rule [53-63]. A mechanical stress in the anastomotic area was the most important cause from the group of ''other'' factors. Movements in the hip area creating this kind of stress are recognized as the reason for the most frequent occurrence of FAA in the inguinal area after aortobifemoral reconstruction [49,55,62,64,65]. Growth of tissue created between the graft and the inguinal ligament prevents the graft from ''sliding'' over the ligament when a hip movement is performed [49]. For this reason, the FAA often develops after aortofemoral reconstruction but rarely develops after axillofemoral, femorofemoral, or femoropopliteal reconstruction. Szilagyi and colleagues believed this is the reason for the FAAs that manifest later [53]. In his discussion of the Stoney and Albo study [47], Baker suggested that anastomosis in the femoral region must be covered by a mobilized sartorius muscle to decrease stress. Mechanical stress caused by insufficient graft length [50] or configuration of end-to-side anastomosis [47,56,66] and the mechanical stress caused by an extensive mismatch, occurring if the prosthesis is too rigid, are also described. With every pulse wave, the anastomotic part of the artery is dilated at least 10% more than the prosthesis. Given that this difference increases with the size of mismatch, the least resistant structures (suture material, artery, prosthesis) could be broken [57,67-70]. These pathogenic mechanisms are more likely to happen on an end-to-side than on an end-to-end anastomosis [66-71]. At first sight, it is normal to expect that FAAs develop more often after the reconstructive procedures performed owing to aneurysmal and not occlusive diseases. In other words, it could be expected that aneurysmal degeneration can enhance FAA development. However, there are not many studies on that.

There are some systemic factors which are thought to contribute to anastamotic aneurysm formation: smoking, hypertension, hyperlipidemia, anticoagulation, systemic vasculitides and generalized arterial weakness [72,73].
