Popliteal Artery Entrapment Syndrome (PAES) - Health

Popliteal artery entrapment syndrome (PAES) is a rare cause of exercise-induced leg pain. Entrapment occurs because of an abnormal relationship between the popliteal artery and the surrounding myofascial structures in the popliteal fossa. Arterial insufficiency in the affected limb arises with entrapment of the artery, commonly giving leg symptoms with exertion.

Popliteal Artery Entrapment Syndrome (PAES) described by Stuart in1879, is an uncommon limb-threatening vascular entity comprising approximately 0.17%-3.5% of the general population in the United States (US)[rx][rx][rx]. This embryologically developmental anomaly results mainly due to an aberrant relationship of the popliteal artery with the surrounding popliteal fossa myofascial structures[rx][rx]. Surprisingly, PAES predominantly affects active young males without a previous history of cardiovascular risk factors[rx].

Pathophysiology of Popliteal Artery Entrapment Syndrome (PAES)

Generally, the majority of the PAES cases are due to the embryological anomalies while fewer patients have been documented having acquired (fibrous bands) causes for the PAES[rx]. Additionally, the PAES are further classified into six different types based on the relationship of the medial head of the gastrocnemius muscle with the popliteal artery[rx].

Type I: An aberrant medial course of the popliteal artery around a normally positioned MHG[rx]
Type II: MHG attaches abnormally and more laterally on the femur causing the popliteal artery to pass medially and inferiorly[rx]
Type III: Abnormal fibrous band or accessory muscle arising from the medial or lateral condyle encircling the popliteal artery[rx]
Type IV: Popliteal artery lying in its primitive deep or axial position within the fossa, becoming compromised by the popliteus muscle or fibrous bands[rx]
Type V: The entrapment of both the popliteal artery and vein due to any of the causes mentioned above[rx]
Type VI: The muscular hypertrophy, resulting in a functional compression of both the popliteal artery and vein[rx]

The functional PAES (Type VI or F) describes another subtype of the disease that is not due to inherited anatomic abnormalities[rx]. It has been postulated that repeated microtrauma results in the growth of connective tissue, destruction of the internal elastic lamina, and damage to the smooth muscles resulting in fibrosis and scar formation[rx]. The resulting injury leads to thrombosis, embolization, and aneurysmal degeneration[rx].

A more straightforward and practical classification system for the PAES was also introduced by Heidelberg.[rx]. According to this classification, the PAES is classified into the following three main types[rx]

Type 1: The problem lies in the course of the popliteal artery[rx]
Type 2: The muscular insertion is atypical[rx]
Type 3: Both of the abovementioned conditions are present[rx]

Causes of Popliteal Artery Entrapment Syndrome (PAES)

Both congenital and acquired mechanisms have been proposed in the development of PAES[7]. An in-depth understanding of the various stages of human embryological development has successfully demonstrated the precise etiology of the congenital PAES.
Developmentally, the popliteal artery and the medial head of the gastrocnemius muscle develop about the same time. Both femoral and sciatic artery contributes significantly to the development of the popliteal artery[7][9]. It originates from the extension of the femoral artery proximally and the sciatic artery distally.
Additionally, the sciatic artery contributes to the development of the tibial arteries as well[9][10]. Over time, the sciatic artery regresses, and the femoral artery becomes the main contributor to the development of the popliteal artery[9].
Popliteal artery entrapment syndrome is a rare abnormality of the anatomical relationship between the popliteal artery and adjacent muscles or fibrous bands in the popliteal fossa.

Symptoms of Popliteal Artery Entrapment Syndrome (PAES)

The main symptom of popliteal artery entrapment syndrome (PAES) is pain or cramping in the back of the lower leg (the calf) that occurs during exercise and goes away with rest. Other signs and symptoms may include:

Cold feet after exercise
Tingling or burning in your calf (paresthesia)
Numbness in the calf area
Heavy feeling in the leg
Lower leg cramping at night
Swelling in the calf area
Changes in skin color around the calf muscle
Blood clots in the lower leg (deep vein thrombosis)

Symptoms typically affect young, otherwise healthy people under age 40.

Diagnosis of Popliteal Artery Entrapment Syndrome (PAES)

Your doctor will carefully examine you and ask questions about your symptoms and health history. However, because most people with popliteal artery entrapment syndrome (PAES) are young and usually healthy, diagnosing the condition can sometimes be challenging. The findings from a physical exam usually are normal.

Your doctor will rule out other causes of leg pain, including muscle strains, stress fractures, chronic exertional compartment syndrome and peripheral artery disease, which results from clogged arteries.

Tests used to rule out other conditions and diagnose PAES include the following

Ankle-brachial index (ABI) measurement is usually the first test done to diagnose PAES. Blood pressure measurements are taken in your arms and legs during and after walking on a treadmill. The ABI is determined by dividing ankle pressure by arm pressure. The blood pressure in your legs should be higher than that in your arms. But if you have PAES, your ankle pressure drops during exercise.
Duplex ultrasound of the calf – uses high-frequency sound waves to determine how fast blood is flowing through the leg arteries. This noninvasive test may be done before or after exercise or while you flex your foot up and down, which puts your calf muscle to work.
Magnetic resonance angiography (MRA) – shows the calf muscle that is trapping the artery. It can also reveal how much of the popliteal artery is narrowed. You may be asked to flex your foot or press it against aboard during this test. Doing so helps your doctor determine how blood is flowing to your lower leg.
CT angiography – also shows which leg muscle is causing the artery entrapment. As with MRA, you may be asked to change the position of your foot during this test.
Catheter-based angiography – allows your doctor to see how blood is flowing to and from the lower leg in real-time. It’s done if the diagnosis is still unclear after other, less invasive imaging tests.

Treatment of Popliteal Artery Entrapment Syndrome (PAES)

The management of the PAES is tailored based on the presence and absence of the symptoms[rx]. For asymptomatic patients with incidental findings of popliteal artery entrapment, management is typically expectant, as the majority of these patients never experience symptoms or disease progression[rx]. On the contrary, if muscle insertion abnormalities are the cause of the PAEs even in an asymptomatic patient, surgical correction is the preferred method of treatment[rx][rx].

Furthermore, for symptomatic PAES patients, surgical resection has been the management of choice [rx][rx]. Surgery with popliteal artery release allows for the definitive re-establishment of normal anatomy and often portends excellent results[rx]. Through either a posterior or medial approach, the MHG or musculotendinous band can be divided. The artery can then be palpated to determine its patency and determine if the bypass is required[rx]. Reconstruction of the adjacent muscles is not necessary as this is well tolerated without functional limitation[rx].

Also, the open surgical procedures offer the best results to address the PAES and assess the artery for repair or bypass[rx]. In cases where there is extensive arterial wall damage, occlusion, or aneurysm development interposition bypass grafting, using autogenous vein via a posterior approach or medial bypass to extend farther down the below-knee popliteal artery have been advocated[rx]. The medial approach may be better for the management of Type I and II, while a posterior approach may be better for type III and IV[rx].

Moreover, the management of functional PAES is still controversial although some have had success with gastrocnemius debulking[rx]. Also, postoperatively, surveillance is performed using arterial duplex imaging at 1, 3, 6, and 12 months, and annually after that[rx].

References

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