Popliteal aneurysms hold an important place in the development of vascular surgery. Because of their accessibility to the examiner's hand and surgeon's scalpel, these were the first aneurysms to be diagnosed before death and to be treated surgically. In the fourth century, Antyllus used the technique of opening the sac after proximal and distal ligation in the popliteal fossa: infection and exsanguinating operative or postoperative haemorrhage were the usual results of this procedure. In the sixteenth century, Ambrose Paré stressed the importance of this operation and this remained the preferred surgical approach to this lesion until the eighteenth century. In 1785, John Hunter, the famous British surgeon, anatomist, physiologist, and pathologist, postulated that ligation of the non-dilated superficial femoral artery in the thigh would be a lesser and safer operation. The patient treated in this manner was a 45-year-old coachman whose symptoms were relieved until he died 15 months later of unrelated causes. The Hunterian ligation held a valuable place in the treatment of popliteal aneurysms for over a century.

Wright Post was the first American surgeon successfully to ligate a popliteal aneurysm in 1814. In 1902, Rudolph Matas of New Orleans began to use his technique of endoaneurysmorrhapy to repair popliteal aneurysms with good results. In the United Kingdom, Hogarth Pringle of Glasgow employed a saphenous vein graft to restore vascular continuity in the repair of a traumatic popliteal aneurysm. A patent graft was found at autopsy several years later. In 1916, 4 years after Pringle, Bertram Bernheim reported the first American experience with vein graft interposition.

Popliteal aneurysms are the most common of peripheral arterial aneurysms and are often associated with other aneurysms, suggesting that there is a generalized pathogenetic mechanism. The two basic factors which contribute to aneurysmal formation are mechanical and mural. The first relates to the mechanical stresses transmitted to the arterial wall, and the latter to the strength and structure of the wall.

Most patients with popliteal aneurysms have arteriosclerosis. This degenerative process is associated with but not necessarily the cause of diffuse weakness of the elastin and collagen structural elements of the media which primarily confer strength on the vessel wall and may predispose a vessel to aneurysmal dilatation. The mechanical stresses which affect the popliteal artery include the systemic stress of hypertension. The artery above a bifurcation is more likely to become aneurysmal, possibly because of reflected pressure waves which cause arterial wall vibration and weaken the vessel wall. Aetiologic factors peculiar to the popliteal artery are the extrinsic stress on the artery from knee flexion and extension and the fixation of the vessel at the adductor hiatus. The presence of an arterial wall diffusely weakened by arteriosclerosis with the superimposition of some or all of these extrinsic and intrinsic mechanical stresses probably causes most popliteal aneurysms. The magnitude of the mechanical factors may determine whether a mild dilatation or a large aneurysm forms and the rate of its development.

Popliteal aneurysms are especially common in patients with arteriomegaly, a condition in which all the vessels show elongation, tortuosity, and diffuse dilatation, with evidence of arteriosclerotic narrowing. Multiple fusiform aneurysms, including those of the popliteal artery, are commonly associated with this condition.

Other less common causes of popliteal aneurysms include penetrating and blunt trauma, microbial arteritis caused by syphilis or other bacterial infection, and popliteal artery entrapment. In the last condition the artery is compressed by an aberrantly inserted gastrocnemius muscle and a post-stenotic aneurysm may develop. However, arteriosclerosis is the most common cause of aneurysm.

A popliteal artery aneurysm is suspected when a prominent expansile impulse can be felt in the popliteal space during physical examination of an asymptomatic patient. Further investigation of such a patient is necessary to confirm the presence of an aneurysm, document its size, and to determine whether mural thrombus is present within the aneurysm. Because of the high incidence of associated aneurysms a search for an occult abdominal aortic aneurysm, femoral aneurysm, and contralateral popliteal aneurysm is part of the evaluation of a patient with a suspected popliteal aneurysm.

The most common and least expensive diagnostic method is ultrasound: ‘B’ mode scanning, usually with the assistance of Doppler ultrasound, allows visualization of the vessel and is quick, accurate, and non-invasive. A popliteal artery dilated to greater than 2 cm diameter or a localized dilatation 1.5 to 2 times the size of the proximal vessel should be considered aneurysmal.

An arteriogram is not a good diagnostic test as it may miss an aneurysm when there is a normal calibre lumen within an aneurysm full of mural thrombus. It is however indicated in the planning of an operation as it defines the arterial anatomy and status of the distal runoff vessels (Fig. 1) 274. Computerized tomography is a useful method of evaluating the popliteal space and provides detail about the arterial wall and intravascular contents, but is more expensive than ultrasound and should not be used for diagnosis. The most useful method of visualization of the popliteal artery is likely to be magnetic resonance imaging scanning, which shows excellent detail of the arterial wall and confirms the presence of mural thrombus. It may also obviate the need for arteriography in patients requiring surgical treatment, as the status of the adjacent arterial anatomy is clearly defined (Fig. 2) 275.

The diagnosis of popliteal aneurysm is suggested by a variety of symptoms. Pain or swelling in the lower leg may be the result of pressure on nerves or venous return. Intermittent claudication, rest pain, or areas of skin necrosis can be the result of thromboemboli from the aneurysm. Rupture is a rare complication and presents with sudden swelling and pain in the popliteal space, sometimes with signs of distal ischaemia. In a patient presenting with acute limb ischaemia, the diagnosis of popliteal aneurysm thrombosis should always be considered and is more likely if a prominent popliteal pulsation suggestive of a popliteal aneurysm is present on the unaffected side. It is important that this diagnosis is made as simple thromboembolectomy is unlikely to help such a patient.

Deposition of marginal laminar thrombus, a phenomenon common to most aneurysms, is responsible for the most frequent complications seen in this condition. Thrombotic and embolic complications are produced by dislodgement of the laminar thrombus within the aneurysm, with obstruction of the popliteal artery outflow tract and thrombosis of the aneurysm, or emboli may obliterate the distal tibial and peroneal arteries, producing severe ischaemia of the lower extremity. If the aneurysm is large, venous obstruction may be mechanically produced and lead to the formation of deep venous thrombosis. Neurological pain syndromes, particularly in the distribution of the sural nerve may also be produced by compression.

Occasionally, a popliteal aneurysm may rupture, but its containment within the popliteal space means that this complication is rarely life-threatening. It does, however, mandate urgent operation because of the severe pain produced and the threat of loss of the extremity secondary to distal arterial occlusion. Also rarely, a popliteal artery aneurysm may become infected as may other peripheral aneurysms.

Linton described the natural history of popliteal aneurysms, reporting a 77 per cent limb loss and a 27 per cent mortality in 22 consecutive aneurysms encountered in 20 patients and treated conservatively. To avoid the high mortality and amputation rates experienced in this condition, operative management is recommended for all but very elderly, poor risk patients. This recommendation is reinforced by the finding of laminar thrombus present within the popliteal aneurysm upon examination by computed tomography or magnetic resonance imaging.

Operative management has the goal of preventing further complications of the aneurysm and restoration of adequate arterial perfusion to the extremity. This goal may be accompanied by bypass grafting of the popliteal aneurysm using autogenous saphenous vein with concomitant proximal and distal ligation of the aneurysm, by resection of the aneurysm with autogenous saphenous vein interposition grafting, or by resection of the aneurysm with end-to-end arterial anastomosis. Bypass grafting with proximal and distal ligation of the aneurysm has become the usual method of operatively managing the moderate sized popliteal aneurysm because of its simplicity of approach.

These techniques are best accomplished by operative exposure through the medial approach to the popliteal fossa, enabling harvest of greater saphenous vein and wide exposure of the arteries involved in the reconstruction through the same incision. This approach also provides the greatest flexibility to the surgeon, allowing more proximal and distal exposure to the arteries, if necessary, to accomplish the arterial reconstruction. Autogenous vein is greatly superior to prosthetic grafts in terms of long-term patency, and in the absence of an available saphenous vein arm veins should be sought for the reconstruction.

If the popliteal aneurysm is large and has produced symptoms attributable to compression of neighbouring veins or nerves the aneurysm should be resected or opened, and its branches ligated from within the aneurysm, prior to the arterial reconstruction. An aneurysm involving a short segment of popliteal artery may be best managed by resection and mobilization of the proximal and distal popliteal artery to allow end-to-end anastomosis without tension. An infected popliteal aneurysm must be resected and autogenous vein utilized in the reconstruction with an initial period of intravenous antibiotic treatment followed by oral antibiotic use indefinitely thereafter. Drug selection should be based initially on the results of Gram stain of the examined material and ultimately on the results of culture and antibiotic sensitivity testing.

Occasionally the clinical presentation may be that of acute arterial occlusion with inability to disobliterate the thrombus within the arterial tree distal to the aneurysm, using the usual method of Fogarty embolectomy catheters. In such circumstances, intraoperative use of urokinase, injected directly as a bolus in the non-perfused distal arterial tree (250 000 IU, reconstituted with 5 ml of sterile water for injection, further diluted with 50 ml 0.97 sodium chloride injection, USP), may be used to clear the distal arterial tree of thrombus, after which grafting around the popliteal aneurysm may be accomplished.

In general, the results of operative management of popliteal artery aneurysms are closely related to the status of the distal arterial tree and to the type of conduit employed. Patients undergoing successful revascularization have good early results. In the Massachusetts General Hospital series, patients with asymptomatic aneurysms treated operatively have uniformly good results (97.2 per cent) compared to those presenting with acute (70.7 per cent), or chronic symptoms (83.3 per cent). At 5-year follow up, 77.2 per cent of all saphenous vein grafts were patent, whereas only 29.5 per cent of Dacron prostheses remained patent.

Anton GE, Hertzer NR, Beven EG, O'Hara PJ, Krajewski LP. Surgical management of popliteal aneurysms. J Vasc Surg 1986; 3: 125–34.

Chitwood WR, Stocks LH, Wolfe WG. Popliteal artery aneurysms. Arch Surg 1978; 113: 1078–82.

Edmunds LH, Darling RC, Linton RR. Surgical management of popliteal aneurysm. Circulation 1965: 32: 517–23.

Evans WE, Vermillion BD. Popliteal aneurysm. In: Wilson SE, Veith FJ, Hoblon RW, Williams RA, eds. Vascular surgery: principles and practice. New York: McGraw-Hill, 1987: 501–3.

Linton RR. The arteriosclerotic popliteal aneurysm. Surgery 1949; 26: 41–58.

MacGowan SW, Saif MF, Fitzsimons P, Bouchier-Hayes D. Ultrasound examination in the diagnosis of popliteal artery aneurysms. Br J Surg 1985; 72: 528–9.

Reilly MK, Abbott WM, Darling RC. Aggressive surgical management of popliteal aneurysms. Am J Surg 1983; 145: 498–502.

Rizzo RJ, Flinn WR, Yao JST, McCarthy WJ, Vogelzang RL, Pearch WH. Computed tomography for evaluation of arterial disease in the popliteal fossa. J Vasc Surg 1990; 11: 112–19.

Weiner SN, Hoffman J, Bertstein RG, Koenigsbery M. The value of ultrasound in the diagnosis of popliteal aneurysm. Angiology 1983; 34: 418–27.

Wychulis AR, Spittell JA, Wallace RB. Popliteal aneurysms. Surgery 1970; 68: 942–52.