Popliteal Aneurysms

The popliteal artery is the second most common site of aneurysms. Knee movements traumatize the artery. In addition, compression of the artery as it leaves Hunter's canal in the lower thigh leads to poststenotic dilation, which is then exacerbated by the development of atherosclerosis. Most lesions are asymptomatic. Patients with a patent aneurysm have pulsatile masses in the popliteal fossa, but an occluded aneurysm may be mistaken for a cyst. Ultrasonography is diagnostic. Other aneurysms should be sought; 50% of patients with a popliteal aneurysm have a popliteal aneurysm in the other leg, and 35% have an abdominal aortic aneurysm.

Thromboembolism--acute or as a series of small emboli to the foot--is the most common complication (16% of patients); it often necessitates amputation. Occasionally, the popliteal pulse disappears and reappears as the thrombus changes position in the aneurysmal sac. Other complications include rupture (in about 10%), popliteal vein compression and thrombosis, and posterior tibial nerve compression with radiating pain or sensory loss in the calf.

Treatment

Patients with occluded aneurysms do not require specific treatment; management is the same as that of peripheral arterial occlusion.

Patent aneurysms, however, are dangerous because of the high risk of rupture and thromboembolism. Surgery is required unless the patient is very debilitated or is expected to die shortly of another cause. Spinal or even local anesthesia can be used, if necessary. The aneurysm is not resected but is bypassed and separated from the circulation by proximal ligation.