Introduction
John Hunter first described popliteal artery aneurysms. They are usually bilateral in 60 to 70 % of cases and are usually associated with abdominal aortic aneurysms. They account for 85 % of peripheral aneurysms. It is more commonly seen in males with a male-female ratio of 15:1. The prevalence of popliteal artery aneurysms increases with age. This condition usually affects individuals in the sixth or seventh decade of life. It is diagnosed by screening or imaging studies. The management depends on the patient's comorbidities, the aneurysms' size, and arterial thrombosis.
What Is an Aneurysm?
An aneurysm is a weak area of the blood vessel that bulges or expands, causing enlargement of the artery. Aneurysms are permanent, irreversible, and life-threatening if they burst.
What Is the Anatomy of Popliteal Artery?
The popliteal artery continues the superficial femoral artery after it passes through the adductor magnus hiatus. The artery lies in the popliteal fossa with its veins. The normal diameter of the popliteal artery is 0.7 to 1.1 centimeters, and it supplies blood to the knee joint, calf, foot, and thighs. The artery is bifurcated into the anterior tibial artery and tibioperoneal trunk and terminates at the tibial tuberosity at the border of the popliteus muscle.
What Is Popliteal Artery Aneurysm?
Popliteal artery aneurysm is the bulging and weakness in the popliteal artery that supplies blood to knee joints, calf, and thighs. It is the focal dilation of the artery, and the diameter of the artery becomes more than 50 % of the normal. Popliteal artery aneurysms may burst and cause uncontrolled bleeding and blood clots, which are life-threatening.
The focal dilation of the artery is of the following two types:
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Fusiform (diffusely dilated).
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Saccular (typically asymmetric and rounded).
Popliteal artery aneurysms are of the following types:
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True popliteal artery aneurysm - Common type and degenerative.
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False popliteal artery aneurysm - Occurs due to trauma, infection, or surgery.
What Are the Causes of Popliteal Artery Aneurysm?
The exact cause of the popliteal artery aneurysm is not known. However, some common causes of popliteal artery aneurysms include the following:
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Atherosclerosis (accumulation of plaque in the arteries causing blockage of blood vessels).
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Post-obstructive angioectasia.
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Trauma to the artery.
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Concurrent cardiovascular diseases.
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Autoimmune disorders.
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High blood pressure.
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Wear and tear of the popliteal artery (due to frequent use of the knee joint).
What Are the Risk Factors Associated With Popliteal Artery Aneurysm?
The following risk factors are associated with popliteal artery aneurysms:
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Smoking.
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Overweight.
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Bechet’s syndrome(an autoimmune disorder causing inflammation of blood vessels).
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Marfan syndrome( a disorder affecting connective tissues).
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Ehler-Danlos syndrome(a genetic connective tissue disorder).
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Advanced age.
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Male gender.
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Family history of aneurysms or vascular diseases.
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High cholesterol and blood pressure.
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Bacterial infection.
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Blood vessel reconstruction in the legs.
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Three or more aneurysms in the body.
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Stenotic diseases (narrowing of heart valves).
What Are the Symptoms of Popliteal Artery Aneurysms?
The symptoms of a popliteal artery aneurysm include the following:
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Pain behind the knee.
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Edema (collection of fluid) in the lower leg.
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Non-healing ulcers on the feet.
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Pulsing sensation behind the knee.
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Foot pain.
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Paresthesias(abnormal tickling or pricking sensation).
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Paresis(partial paralysis or weakness).
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Pallor(unusual lightness of skin complexion).
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Poikilothermia(poorly regulated body temperature).
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Claudication(cramping pain in the lower leg).
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Gangrene (tissue death).
How to Diagnose Popliteal Artery Aneurysms?
The diagnostic procedures for a popliteal artery aneurysm include the following:
1.Physical Examination: Healthcare providers will take a detailed family and medical history of the patients.They conduct physical examinations to check for swelling, tenderness, signs and symptoms of restricted blood flow, skin color changes (pallor), excruciating pain, and coldness in the lower leg or behind the knee.
2. Duplex Ultrasonography:
- It is the ideal modality to diagnose popliteal artery aneurysms and the diameter of the blood vessels.
- It also provides information about vessel patency, the status of outflow vessels, and thrombus development.This test uses sound waves to diagnose blood flow.
3.Computed Tomography(CT) or Magnetic Resonance Angiography:
- Magnetic resonance angiography provides detailed images of blood flow in the blood vessels.It measures thelumen diameter and helps in treatment planning.
What Are the Differential Diagnosis of Popliteal Artery Aneurysms?
The differential diagnosis of popliteal artery aneurysms includes the following:
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Lymphadenopathy(swollen lymph nodes).
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Varicosity(dilation of veins in lower legs).
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Popliteal cysts (Baker’s cyst).
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Other cysts in the popliteal artery (for example, synovial sarcoma).
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Cystic adventitial diseases of the popliteal artery.
How to Manage Popliteal Artery Aneurysms?
Managing popliteal artery aneurysms depends on the patient's health, age, and complexity. Management is divided into symptomatic and asymptomatic patients.
1.Asymptomatic Patients:
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Asymptomatic patients with aneurysms under two centimeters are managed with duplex ultrasound surveillance to monitor the size of the aneurysm, thrombus, and embolus formation.
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Patients should follow lifestyle measures to reduce the risk of cardiovascular diseases.
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Drugs such as antiplatelets, statins, and antidiabetic drugs are prescribed.
2. Open Surgical Approach:
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Traditional surgery involves the surgical exclusion of popliteal aneurysms.
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The surgery involves ligating the popliteal artery above the knee and below the aneurysmal sac.
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The excluded segment is bypassed using reversed autologous vein graft (more commonly saphenous vein) or prosthetic graft.
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Endoaneurysmorrhaphy involves the opening of the aneurysms and graft placement within it.
- Aneurysmectomy is the interposition bypass with a prosthetic graft between the proximal and distal segments of normal popliteal artery aneurysms.
3. Endovascular Approach or Keyhole Surgery:
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It is an alternative option to the open surgical approach.
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The surgery includes stent-graft implantation (fabric-lined metal mesh).
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The stent is placed across the aneurysm to exclude the aneurysm from circulation.
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It is a safe alternative option for high-risk patients.
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The advantage of the endovascular approach is shorter hospital stays.
4. Management of Acutely Thrombosed Aneurysms:
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Intravenous Heparin continuously treats acute thrombosis to limit the thrombus's extension.
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Patients with acute limb ischemia require immediate attention and surgical emergency.
- Management of patients with acute limb ischemia includes opiate analgesia, resuscitation, and anticoagulation.
5. Intra-Arterial Thrombolytic Therapy:
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This method is indicated when multiple distal thrombi are present.
What Are the Complications of Popliteal Artery Aneurysms?
The complications of popliteal artery aneurysms include the following:
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Limb loss.
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Distal thromboembolization.
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Aneurysm rupture (rare).
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Pressure affects the surrounding structures, such as the popliteal vein and tibial nerve.
Conclusion
The prognosis is poor for patients with ruptured aneurysms. Smoking and high blood pressure increase the risk of vascular aneurysms. The healthcare team advises people to follow a healthy lifestyle, such as a nutritious diet and regular exercise, to prevent popliteal artery aneurysms.
