Superficial Femoral to Below-the-Knee Popliteal Artery Bypass for Popliteal Artery Aneurysm Containing Mural Thrombus

Abstract

Popliteal artery aneurysms (PAAs) are the most common peripheral arterial aneurysms, with an incidence of approximately 10.4 cases per million per year and occur most frequently in men aged 60–70 years. Many lower extremity aneurysms are asymptomatic and are discovered incidentally on physical examination or imaging performed for unrelated conditions. However, symptoms resulting from compression of surrounding structures can occur and may be disabling, including deep vein thrombosis and neuropathies. The most serious complication is acute limb ischemia resulting from thrombosis or distal embolization. For this reason, the Society for Vascular Surgery (SVS) clinical practice guidelines recommend operative repair when an asymptomatic aneurysm reaches 20 mm in diameter or contains mural thrombus.

We present the case of a 67-year-old male with a 22-mm right PAA with significant mural thrombus. Given his right PAA was greater than 2 cm and had significant mural thrombus, he was evaluated for intervention. An intraoperative angiogram identified proximal and distal sites for bypass that were free of mural thrombus. Therefore, the patient underwent a superficial femoral to below-the-knee popliteal artery bypass using a great saphenous vein conduit through a medial incision in the supine position. The superficial femoral artery and below-the-knee popliteal artery were dissected free from the surrounding structures. The case required local thromboendarterectomy of the below-the-knee popliteal artery and tibioperoneal (TP) trunk, due to the presence of chronic thrombus at the endpoint that was not able to be visualized on preoperative angiography. A bypass was created between the two arteries, and the native artery was ligated, including the aneurysm. 

The case highlights operative management of a PAA as well as the techniques involved in lower extremity bypass. Lower extremity bypass remains an important procedure for vascular and trauma surgeons who may need to perform this procedure for multiple pathologies.

Keywords

Lower extremity bypass; popliteal artery aneurysm; great saphenous vein conduit.

Case Overview

Background

Arterial aneurysms are defined as a dilation of a blood vessel at least 1.5–2 times the normal diameter of a vessel involving all three layers of the arterial wall.¹ Aneurysms affect different arteries with varying frequencies and clinical consequences. Popliteal artery aneurysms (PAAs) are the most common peripheral arterial aneurysm, accounting for 70–85% with an incidence of 10.4 cases per million per year, most commonly in 60- to 70-year-old men.^2–4 The common femoral artery (CFA) is the second most common site of peripheral artery aneurysm. The superficial femoral artery (SFA) can also become aneurysmal, but SFA aneurysms are much less frequent and mostly occur proximally in the groin.⁵ Aneurysms are described as asymptomatic or symptomatic. Many lower extremity aneurysms are asymptomatic and discovered incidentally on physical exam or imaging.^3,6 Symptoms of lower extremity peripheral aneurysms can include acute limb ischemia, secondary to thrombosis or embolization, and compression of veins or nerves causing deep vein thrombosis (DVT), pain, or neuropathy.^2,6–9 While rupture is the classic complication of abdominal aneurysmal disease, lower extremity aneurysms have a relatively low risk of rupture because the surrounding muscles and tendons provide mechanical support and confinement.^10,11 

Current Society for Vascular Surgery (SVS) clinical practice guidelines for PAAs recommend intervention for asymptomatic aneurysms with significant thrombus, suspicion of distal embolization, or diameters greater than or equal to 20 mm.¹² Intervention is also recommended for symptomatic aneurysms producing thrombotic or embolic complications. Given the infrequency of other lower extremity aneurysms, there are no formal SVS guidelines outside of PAAs; however, treatment should be considered for lower extremity aneurysms that produce symptoms or when the diameter is greater than or equal to 25 mm.^13,14 

Options for intervention include both open and endovascular approaches, with SVS guidelines recommending open surgical bypass using a saphenous vein conduit with aneurysm ligation as the current standard of care.¹² However, the volume of lower extremity bypass has decreased with the advent of endovascular interventions that may be more suitable for older patients or those with significant comorbidities.^15,16 

In this article and accompanying video, we provide a case of a patient with a large, asymptomatic PAA who underwent superficial femoral to below-the-knee popliteal artery bypass. This case highlights the role of open surgical management for peripheral arterial aneurysms using a great saphenous vein conduit when available.

Focused History of the Patient

A detailed history should assess symptoms related to peripheral aneurysms and risk factors that predispose aneurysm development. Key elements include noticeable leg edema, from venous compression, neuropathies from nerve compression, and claudication or tissue loss from distal embolization. Predisposing factors include a prior history of smoking and a family history of aneurysms.¹⁷ Patients should also be evaluated for additional aneurysms, where over 15% of patients with abdominal aortic aneurysms (AAA) have a PAA.¹⁸

A history of prior surgical interventions for peripheral arterial disease, venous insufficiency, or coronary artery disease is important to understand the anatomy and the availability of vein conduits. Comorbid conditions should also be documented. These factors may influence procedural planning and overall perioperative risk stratification. Medication history should include immunosuppressive therapies that may impair wound healing and antiplatelet or anticoagulant medications that may require temporary cessation prior to surgery.

Our patient is a 67-year-old male with hypertension, hyperlipidemia, type 2 diabetes mellitus, and obesity with a body mass index (BMI) of 29.5 kg/m². He had a history of aneurysmal disease that includes a 4.5-cm infrarenal aortic aneurysm, bilateral CFA aneurysms measuring 17 mm on the right and 24 mm on the left, and bilateral PAAs measuring 29 mm on the left and 22 mm on the right. Although he was offered repair for his bilateral PAAs in the past, he declined given his asymptomatic status and opted for medical management and surveillance. In 2024, the patient developed left lower extremity pain with mottling, and he was diagnosed with acute limb ischemia secondary to a thrombosed left-sided PAA. He underwent emergent left SFA to below-the-knee popliteal artery bypass utilizing ringed polytetrafluoroethylene (PTFE) along with fasciotomies. Fortunately, the patient recovered well with some residual neuropathy in the left foot. Given his acute event, the patient was started on apixaban and referred back to vascular surgery for repair of his right PAA. On our evaluation, the patient’s right PAA was asymptomatic. He walked about 5,000–6,000 steps per day. The patient was classified as American Society of Anesthesiologists (ASA) class III due to multiple comorbidities and a prior episode of acute limb ischemia.

Physical Exam

Lower extremity interventions require a thorough lower extremity exam, including inspection of the skin for ulceration or scars from previous surgery. Embolic disease can produce foot ulceration and areas of ischemia that have a bluish hue, commonly called blue toe syndrome.³ A vascular exam should be documented both before and after revascularization for comparison. Lastly, motor function and sensation should be documented prior to intervention to assess for any nerve injuries postoperatively.

In our case, the patient had bilateral palpable femoral pulses, but his distal pulses were not palpable. He had Doppler signals in his right posterior tibial, right dorsalis pedis arteries, and left posterior tibial artery. He had well-healed left lower extremity scars. There were no pedal wounds, and motor function and sensation were intact in bilateral lower extremities in all nerve distributions.

Imaging

Although duplex ultrasound is the recommended modality for surveillance of peripheral arterial aneurysms, it often does not adequately visualize distal runoff vessels, and there are no current standard reporting criteria.¹⁹ Distal arterial anatomy is best visualized using either computed tomography angiography (CTA) or a lower extremity arterial angiogram.²⁰ These imaging modalities allow for evaluation of additional aneurysms and provide assessment of distal embolization by visualizing runoff vessels. However, distal vessels are more clearly delineated with direct angiography. Preoperative ultrasound evaluation of vein conduits is also recommended, as evidence suggests that autogenous vein conduits are more durable than prosthetic conduits.²¹

In this case, the patient underwent preoperative CTA. His left SFA to popliteal artery bypass was patent with three-vessel runoff. CTA demonstrated a 22-mm right PAA containing mural thrombus and a 15-mm fusiform right SFA aneurysm. The contrast was not timed adequately to delineate the tibial vessels, due to atherosclerotic disease, slowed flow, and lack of delayed imaging. Therefore, an intraoperative angiogram was planned to identify the proximal and distal target vessels. He also underwent evaluation for great saphenous vein (GSV) conduit with an ultrasound that showed adequate vein conduit greater than 3 mm in diameter.

Natural History

PAAs are less prone to rupture than other aneurysms; however, they carry a substantial risk of thrombosis and distal embolization, resulting in acute limb ischemia, tissue loss, and occlusion of tibial vessels leading to limb loss. The risk of thromboembolic events increases with larger aneurysm diameter and a higher burden of mural thrombus. Over time, most noncalcified aneurysms demonstrate progressive enlargement.⁹

Data describing the natural history of PAAs remains limited, mostly focusing on operative outcomes or aneurysm growth rates. A systematic review identified only three studies evaluating natural history in predominantly European male populations over the age of 70.²² In one early study, thromboembolic complications and amputations occurred at a mean observation time of 18 months.² In a series of 131 PAAs, 27% experienced complications during a median follow-up of 33 months.⁹ Across these natural history studies, no consistent association between clinical variables and PAA-related adverse events was identified.

Studies evaluating aneurysm growth have identified hypertension²³ and atrial fibrillation²⁴ as factors associated with more rapid expansion. Additional markers have been investigated to better risk stratify patients, including the percentage of mural thrombus burden.²⁵ Ultimately, the primary objective of surgical management of PAAs is prevention of thromboembolic complications rather than simply limiting aneurysm enlargement.

Options for Treatment

Management of PAAs includes both open and endovascular approaches, with treatment selection guided by anatomic considerations, patient comorbidities, and the urgency of presentation. In the elective setting, treatment typically involves bypass or aneurysmorrhaphy using autogenous vein conduit.¹² For patients with compressive symptoms, operative management should also include decompression of the aneurysm sac. Endovascular treatment with covered stent grafting may be considered in patients who are high risk for general anesthesia or who have limited life expectancy.^3,12

The urgency of the clinical presentation also influences treatment strategy. Patients presenting with higher severity of ischemia (Rutherford’s grade IIb) should receive immediate revascularization. For patients with less severe ischemia (Rutherford’s grade I or IIa), angiography with thrombolysis may be considered to improve the outflow vessel patency, with a plan for interval bypass.

Rationale for Treatment

The goal for elective treatment of asymptomatic PAA is to decrease the risk of acute limb ischemia due to embolism or thrombosis. There is a higher risk for this with higher percentage of thrombus and larger diameter.^4,25 Intraoperatively, the goal is to establish in-line flow between healthy, nonaneurysmal arterial segments, whether achieved through bypass or endoaneurysmorrhaphy.

Special Considerations

Patients who are at high risk for general anesthesia or have a limited life expectancy should be considered for endovascular options or even observation given the potential morbidity and mortality associated with surgical bypass.²⁶ There have been mixed reports regarding the use of anticoagulation to prevent thrombosis or distal embolization, which represents an area of further study.²⁷

Discussion

This case demonstrates a successful lower extremity bypass for a 22-mm right PAA containing mural thrombus. Diagnostic angiograms were performed at the beginning of the procedure to ensure patent distal vasculature. The case required approaches to the SFA and below-the-knee (BTK) popliteal artery, as well as harvesting the GSV for the conduit. Following tunneling in the anatomic position of the native artery, end-to-end anastomoses were performed at each level followed by ligation of the native, aneurysmal artery. Angiography was also performed at the conclusion of the procedure to ensure adequate flow and to assess for complications, which did demonstrate a need for additional dissection around the bypass to release a tethering muscular band. The procedure length was just under nine hours with an estimated blood loss of 700 mL. The patient had a six-day hospital stay and was subsequently discharged to inpatient rehab for further strengthening and mobility without any complications. 

PAAs are the most common peripheral aneurysm, but they are still rare with a prevalence of 1% in screened asymptomatic men between the ages of 65–80.²⁸ The patient in this case has a propensity to aneurysm formation given his AAA, right SFA aneurysm, and bilateral PAAs. His left PAA presented as acute limb ischemia, a common presenting symptom leading to an estimated 8% rate of limb loss.²⁹ Fortunately, the patient’s left leg was salvaged, and he decided to pursue intervention for his right leg. In the interim prior to surgical intervention, he was started on apixaban. Oral anticoagulation for embolization is not well studied for prophylaxis in conservative management of PAAs. A case study supporting oral anticoagulation showed benefit in a large PAA without complications, although no randomized controlled studies or direct comparisons have been performed.³⁰ The SVS supports the use of antiplatelets, but the guidelines do not support anticoagulation without any substantial benefit due to the bleeding risk.¹² 

Preoperative imaging was critical to identifying significant mural thrombus in his aneurysm that could predispose the patient to embolic events. Prior to performing the bypass, further imaging in the form of a dynamic angiogram was performed to better delineate healthy artery above the popliteal artery and confirm a distal outflow target for the bypass. The patient’s SFA was aneurysmal; however, the PAA was more prominent and contained mural thrombus. In order to decrease the length of the bypass and the conduit needed, a portion of the SFA free of mural thrombus was chosen as the donor artery. Duplex ultrasound was performed intraoperatively prior to the procedure to ensure the GSV correlated with preoperative ultrasound, which showed adequate size for bypass. Veins measured at least 3 mm are recommended as smaller sizes may increase the rate of failure.³¹ Despite extensive preoperative and intraoperative imaging, thrombus cannot always be visualized adequately. This case additionally required a local thromboendarterectomy of the BTK popliteal artery and TP trunk, due to the presence of chronic thrombus at the endpoint that was not able to be visualized on preoperative angiography. Thus, it is important to keep a high index of suspicion of thrombus and minimize the chance of embolization when mobilizing the arteries and deciding clamping order. 

PAAs are traditionally treated with open techniques, which include medial or posterior approaches. The medial approach is preferential for aneurysms that are not confined to the popliteal fossa. This approach allows for more extensive dissection that can span from the femoral to the tibial vessels. This approach requires ligation of the native artery, but the aneurysm can continue to expand due to geniculate collaterals.³² The posterior approach is performed in the prone position and utilizes a lazy-S incision to dissect the popliteal fossa. This allows for opening of the aneurysm sac and decompression of thrombus. Decompression is helpful when PAAs are causing compression of the adjacent nerve or vein. The artery is repaired via endoaneurysmorrhaphy utilizing a vein or prosthetic graft as an interposition graft.³³ Vein and prosthetic grafts in this position have similar patency and adverse limb events.³⁴ Lastly, the aneurysm sac is closed around the interposition graft.³³ PAAs can also be treated endovascularly with stent graft exclusion, which offers a less invasive option for frail patients. Patients undergoing endovascular treatment require 20 mm of healthy artery proximal and distal to the aneurysm and at least two-vessel runoff to the foot.³² The SVS guidelines recommend consideration of an endovascular approach for patients with a life expectancy of less than five years.¹²

While there are no randomized controlled studies comparing open and endovascular approaches, there has been debate regarding the optimal approach for repair. Several comparative studies have suggested advantages to open repair, including higher primary patency in the POPART registry,²⁷ lower rates of major amputation,³⁵ and fewer major adverse limb events at one year in the Vascular Quality Initiative.³⁶ However, other studies have reported no significant differences between open and endovascular repair in terms of primary or secondary patency at two years,^26,37 major adverse limb events (MALE),³⁸ or amputation-free survival in the large multicenter PARADE study.³⁹ Concerns regarding endovascular treatment primarily relate to long-term durability as a meta-analysis comparing open and endovascular repair demonstrated significantly lower primary patency with stent grafting, although secondary patency at three years was similar between approaches.⁴⁰

PAAs increase the risk of limb loss due to embolization and thrombosis. Repair is recommended for symptomatic aneurysms and asymptomatic aneurysms with significant mural thrombus or size greater than 20 mm. Open repair is the gold standard, which has two approaches depending on the extent of the aneurysm. Our case highlights an asymptomatic PAA treated through a medial approach utilizing an SFA-to-BTK popliteal artery vein bypass with interval ligation of the aneurysm. The patient recovered well without any complications and adequate healing of the medial leg incisions (Figure 1). The case highlights management of a PAA as well as the techniques involved in lower extremity bypass, including preoperative imaging modalities and completion angiogram. Lower extremity bypass remains an important procedure for vascular and trauma surgeons who may need to perform this procedure for multiple types of pathology.

Figure 1. Postoperative medial leg incisions.

Equipment

The procedure was done in a hybrid endovascular surgical suite due to the need for endovascular evaluation during the procedure. The initial angiogram utilized a micropuncture kit and 4-Fr sheath (Merit Medical), a 5-Fr introducer sheath (Pinnacle), a Safe-T-J 3-mm tip 0.035-in wire (Cook Medical), and a 5-Fr Soft-vu Omni flush catheter (Angiodynamics). Contrast angiography was performed with the use of a power injector.  

A standard open vascular bypass tray was used for the open portion. This included a long tunneler to pass the conduit to each position of the bypass.

Disclosures

We report no conflicts of interest, financial relationships, funding, sponsorship, equipment support, or other relationships that could be perceived to influence the content of this article.

Statement of Consent

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.