BACKGROUND

Popliteal artery aneurysms (PAAs) are the most common form of peripheral arterial aneurysms. The popliteal artery is the continuation of the femoral artery and represents the major source of blood to the leg. Thrombus formation as a result of PAA may reduce blood flow, leading to limb-threatening ischaemia and potential limb amputation. PAAs are predominantly seen in men (90% of cases), presumably owing to their predisposition for arteriosclerosis, which is also a major factor for PAA predisposition.1

Surgical treatments for PAA are to isolate and exclude the aneurysm, prevent distal embolisation, and allow effective revascularisation. Limb salvage is low in patients with symptomatic PAAs, particularly in those with acute ischaemia; it is higher for asymptomatic patients.

CASE PRESENTATION

A 64-year-old obese man was admitted to our institution with right lower limb pain of 2 months aggravated by walking and oedema. There was no prior history of claudication. In the physical examination, a pulsatile mass was identified in the right popliteal area, and right distal leg pulses were non-palpable. There was significant neurological deficiency, with foot drop on the right foot. Aneurysmal enlargement was demonstrated with colour Doppler examination and magnetic resonance angiographic evaluation. These examinations revealed a thrombotic PAA (80×110 mm) with arteriomegaly and deep venous thrombosis (figs 1 and 2). Under general anaesthesia, a curved skin incision was made along the anterior border of the sartorius muscle in the lower one-third of the thigh and extended across the knee, along the posteriomedial edge of tibia (fig 3A).

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Figure 1

MRI of the popliteal aneurysm.

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Figure 2

Magnetic resonance angiographic view of the popliteal aneurysm.

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Figure 3

(A–D): The stages of the operative procedure.

The sartorius, semimembranous, gracilis and semitendinous muscles were identified and transected at their lower insertions and the aneurysm was explored. After systemic heparinisation, the popliteal artery was clamped above and below the aneurysm. The aneurysm sac was adherent to the adjacent tissues. The aneurysm sac was entered and a huge amount of organised thrombus material was removed (fig 3B). After this, graft interposition was performed using a 10 mm polytetrafluoroethylene (PTFE; Atrium, Hudson, New Hampshire, USA) graft between the distal and proximal ends of the popliteal artery through an end-to-end anastomosis (fig 3C). After the vascular procedure was completed, the tendons and muscular structures were reconstituted (fig 3D).

OUTCOME AND FOLLOW-UP

After a normal postoperative course, the patient was discharged on postoperative day 9. His physical examination was normal with palpable popliteal and distal pulses on the postoperative 10th month.

DISCUSSION

PAAs are the most common peripheral arterial aneurysms and the second most common aneurysm after abdominal aortic aneurysms. They have historically been associated with a high rate of limb loss. Since John Hunter first called attention to PAAs more than four centuries ago, several large series have been published that have helped define the natural history, clinical presentation, operative treatment, and long-term limb salvage and survival outcomes for patients with such aneurysms.1^–7 PAAs can cause critical, acute limb ischaemia after acute vessel thrombosis, distal embolisation, and, less commonly, rupture. Asymptomatic and symptomatic aneurysms of ⩾2 cm in diameter are considered candidates for elective surgery. Until recently, surgery was the standard form of treatment for all symptomatic aneurysms and for large asymptomatic aneurysms. More recently, endovascular repair of a PAA has proven to be a viable treatment option.8^,9

The diagnosis of PAAs is not straightforward because of their non-specific manifestations. There may be a pulsatile mass at the popliteal region unless the aneurysm is thrombotic. It is suggested that nearly one-third of the patients with PAA are asymptomatic at the time of diagnosis.6 The prevalence of PAA is 1% in the general population; it is often bilateral and associated with abdominal aortic aneurysms.2^,4 Thrombus within an aneurysm is an indication for elective surgery whatever the size of the PAA.5 Surgical intervention of an asymptomatic PAA has a high limb salvage rate and better outcome than symptomatic aneurysms. Such aneurysms dictate surgical removal as they may cause ischaemia and amputation. The surgical approach usually consists of bypass using autogenous and sometimes synthetic grafts. In our case there was a giant aneurysm causing venous stasis leading to claudication. We used a synthetic PTFE graft as a conduit.

Non-surgical treatment of PAA is another topic open to discussion. Recently, with the advances in endovascular techniques, especially in aortic aneurysms, peripheral aneurysms have also become candidates for this conservative approach. Endovascular approach has some advantages over surgical repair in lower extremity aneurysms as it does not cause high amounts of bleeding, the patients recover in a short period of time, and the hospital stay is shorter.7^,8 However, this technique has some disadvantages where PAA is concerned and it is reported that stents at the popliteal region are not as effective as for femoral or iliac aneurysms.8 Because the popliteal artery is a branching artery and it is located at the knee joint, endografts may kink during knee joint movement, and kinking of the grafts may cause important problems.9 Elective surgery seems to be the better alternative since it has high graft patency and limb salvage rates. Although endovascular stent grafting is easy to perform and leads to good outcomes in moderate-size aneurysms, it may not be preferred in giant aneurysms with increased volume, venous stasis and nerve compression.

Aneurysm size plays less of a role in the decision to treat popliteal artery aneurysms compared with aneurysms in other locations, such as the abdominal aorta. This is because the major morbidity from popliteal artery aneurysms is due to thromboembolism rather than rupture. Thus, symptomatic aneurysms require repair regardless of size. Other indications include aneurysms of any size that contain intramural thrombus and asymptomatic aneurysms that are >2 cm in size. Amputation rates vary from 16% to 43% in patients presenting with severe ischaemia. In elective repair of these aneurysms, however, the limb loss is <1%.7^,10

Asymptomatic patients develop ischaemic symptoms between 18% and 31% of the time, and this accounts for the majority of the 2–13% of this population that eventually require amputation.11 Due to the low mortality and complication rates of operative repair in contrast to the high morbidity rate when symptoms develop, most surgeons would proceed to repair any popliteal artery aneurysm >2 cm.

In fact, small PAAs have traditionally been followed with serial ultrasound. Several studies have suggested that these aneurysms have a higher rate of thromboembolism than larger aneurysms. This would suggest that the threshold for operative intervention should be lower than the current guidelines and some investigators advocate operating on all PAAs.12