popliteal artery entrapment syndrome
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The popliteal artery entrapment syndrome (PAES) is an uncommon
pathology Pathology is the study of the causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in ...
that occurs when the popliteal artery is compressed by the surrounding popliteal fossa myofascial structures. This results in
claudication Claudication is a medical term usually referring to impairment in walking, or pain, discomfort, numbness, or tiredness in the legs that occurs during walking or standing and is relieved by rest. The perceived level of pain from claudication can be ...
and chronic leg
ischemia Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems wi ...
. This condition mainly occurs more in young athletes than in the elderlies. Elderlies, who present with similar symptoms, are more likely to be diagnosed with
peripheral artery disease Peripheral artery disease (PAD) is an abnormal narrowing of arteries other than those that supply the heart or brain. When narrowing occurs in the heart, it is called coronary artery disease, and in the brain, it is called cerebrovascular diseas ...
with associated
atherosclerosis Atherosclerosis is a pattern of the disease arteriosclerosis in which the wall of the artery develops abnormalities, called lesions. These lesions may lead to narrowing due to the buildup of atheroma, atheromatous plaque. At onset there are usu ...
. Patients with PAES mainly present with intermittent feet and calf pain associated with exercises and relieved with rest. PAES can be diagnosed with a combination of medical history, physical examination, and advanced imaging modalities such as
duplex ultrasound Doppler ultrasonography is medical ultrasonography that employs the Doppler effect to perform imaging of the movement of tissues and body fluids (usually blood), and their relative velocity to the probe. By calculating the frequency shift of a ...
, computer tomography, or
magnetic resonance angiography Magnetic resonance angiography (MRA) is a group of techniques based on magnetic resonance imaging (MRI) to image blood vessels. Magnetic resonance angiography is used to generate images of arteries (and less commonly veins) in order to evaluate t ...
. Management can range from non-intervention to open surgical decompression with a generally good prognosis. Complications of untreated PAES can include stenotic artery degeneration, complete popliteal artery occlusion, distal arterial thromboembolism, or even formation of an
aneurysm An aneurysm is an outward bulging, likened to a bubble or balloon, caused by a localized, abnormal, weak spot on a blood vessel wall. Aneurysms may be a result of a hereditary condition or an acquired disease. Aneurysms can also be a nidus (s ...
.


History

In 1879, the syndrome was first described in a 64 years old male by Anderson Stuart, a
medical student A medical school is a tertiary educational institution, or part of such an institution, that teaches medicine, and awards a professional degree for physicians. Such medical degrees include the Bachelor of Medicine, Bachelor of Surgery (MBBS, MB ...
. In 1959, Hamming and Vink first described the management of the PAES in a 12-year-old patient. The patient was treated with
myotomy Myotomy is a surgical procedure in which muscle is cut. A common example of a myotomy is the Heller myotomy. See also * List of surgeries by type Many surgical procedure names can be broken into parts to indicate the meaning. For example, in ...
of the medial head of the
gastrocnemius muscle The gastrocnemius muscle (plural ''gastrocnemii'') is a superficial two-headed muscle that is in the back part of the lower leg of humans. It runs from its two heads just above the knee to the heel, a three joint muscle (knee, ankle and subtala ...
an
concomitant
endarterectomy Endarterectomy is a surgical procedure to remove the atheromatous ''plaque'' material, or blockage, in the lining of an artery constricted by the buildup of deposits. It is carried out by separating the plaque from the arterial wall. It was firs ...
of the popliteal artery. They later reported four more cases and claimed that the incidence of this pathology in patients younger than 30 years old with claudication was 40%. Servello was the first to draw attention to diminished distal pulses observed with forced plantar- or dorsiflexion in patients with this syndrome. In 1981, Bouhoutsos and Daskalakis reported 45 cases of this syndrome in a population of 20,000 Greek soldiers. Over the last few decades, the increasing frequency with which popliteal artery entrapment is reported, strongly suggests greater awareness of the syndrome.


Epidemiology

In the general population, popliteal artery entrapment syndrome (PAES) has an estimated
prevalence In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...
of 0.16%. It is most commonly found in young, physically active males. In fact, sixty percent of all cases of this syndrome occur in athletically active males under the age of 30. The predilection of this syndrome presents in a male to female ratio of 15:1. This discrepancy in prevalence may be overestimated due the findings that males are generally found to be more physically active than females or because a large portion of the data is from military hospitals that treat mostly male populations. People, who participate in running, soccer, football, basketball, or rugby, are at increased risk. Newborns and young children are also at increased PAES risk due to congenital causes. During
embryonic development An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm ...
, the medial head of
gastrocnemius The gastrocnemius muscle (plural ''gastrocnemii'') is a superficial two-headed muscle that is in the back part of the lower leg of humans. It runs from its two heads just above the knee to the heel, a three joint muscle (knee, ankle and subtalar ...
migrates medially and superiorly. This migration can cause structural abnormalities, such as irregular positioning of the
popliteal artery The popliteal artery is a deeply placed continuation of the femoral artery opening in the distal portion of the adductor magnus muscle. It courses through the popliteal fossa and ends at the lower border of the popliteus muscle, where it branches ...
, and can account for the rare instances of entrapment caused by the
popliteus muscle The popliteus muscle in the leg is used for unlocking the knees when walking, by laterally rotating the femur on the tibia during the closed chain portion of the bipedal gait cycle, gait cycle (one with the foot in contact with the ground). In op ...
. Less than 3% of all people are born with this anatomical defect that progresses into PAES, and of those who are born with the anatomical defect, the majority never develop
symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showin ...
s. Bilateral presentation of PAES is found in approximately 30% of cases.


Pathophysiology and classification

PAES can be classified as either congenital or functional. Analysis of human embryological development has shown that the popliteal artery and the medial head of the gastrocnemius muscle arise at approximately the same time. Because of that, abnormal development of muscle's position in relation to the nearby vessels can result in potential vascular compromise. The varying types of PAES can be classified based on aberrant migration and resultant attachments of the medial head of the gastrocnemius muscle. Type VI PAES (functional PAES) describes a subtype that is due to repeated
microtrauma Microtrauma is any of many possible small injuries to the body. Microtrauma can include the microtearing of muscle fibres, the sheath around the muscle and the connective tissue. It can also include stress to the tendons, and to the bones (see ...
resulting in the destruction of the internal elastic lamina and damage to the smooth muscles resulting in
fibrosis Fibrosis, also known as fibrotic scarring, is a pathological wound healing in which connective tissue replaces normal parenchymal tissue to the extent that it goes unchecked, leading to considerable tissue remodelling and the formation of perma ...
and scar formation. Additionally, a more practical classification system was introduced by Heidelberg et al. This system classifies PAES into three main types: * Type 1: The problem lies in the abnormal position of the popliteal artery. * Type 2: The problem lies in the abnormal insertion of the medial head of the gastrocnemius muscle. * Type 3: Both types 1 and 2 are present.


Medical history and physical examination

Patients with PAES are typically healthy young males without previous history of cardiovascular risk factors such as smoking,
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
,
hypercholesterolemia Hypercholesterolemia, also called high cholesterol, is the presence of high levels of cholesterol in the blood. It is a form of hyperlipidemia (high levels of lipids in the blood), hyperlipoproteinemia (high levels of lipoproteins in the blood), ...
, or
diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
. Typically, patients present with
intermittent claudication Intermittent claudication, also known as vascular claudication, is a symptom that describes muscle pain on mild exertion (ache, cramp, numbness or sense of fatigue), classically in the calf muscle, which occurs during exercise, such as walking, and ...
that is worsened with exercise and relieved with rest. Associated symptoms include numbness, discoloration, pallor, and coolness in the affected lower extremity. Physical examination of suspected PAES may show
hypertrophy Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It is distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number.Updated by Linda J ...
of the calf muscles, as well as diminished, unequal, or absent pulses in the lower extremity upon plantar- or dorsiflexion.


Diagnosis


Differential diagnosis

* Chronic exertional
compartment syndrome Compartment syndrome is a condition in which increased pressure within one of the body's anatomical compartments results in insufficient blood supply to tissue within that space. There are two main types: acute and chronic. Compartments of the ...
: Chronic pain and swelling of the affected muscle secondary to increase intramuscular pressure during exercise. * Unresolved muscle
strain Strain may refer to: Science and technology * Strain (biology), variants of plants, viruses or bacteria; or an inbred animal used for experimental purposes * Strain (chemistry), a chemical stress of a molecule * Strain (injury), an injury to a mu ...
: An injury or damage to the muscle or its attaching tendons. *
Medial tibial stress syndrome A shin splint, also known as medial tibial stress syndrome, is pain along the inside edge of the shinbone ( tibia) due to inflammation of tissue in the area. Generally this is between the middle of the lower leg and the ankle. The pain may be dul ...
: Pain occurs over the shin bone (the tibia) with running or other sport-related activity. * Fibular and tibial
stress fracture A stress fracture is a fatigue-induced bone fracture caused by repeated stress over time. Instead of resulting from a single severe impact, stress fractures are the result of accumulated injury from repeated submaximal loading, such as running or ...
: Non-displaced microscopic fracture of the fibular and tibia occurs in many athletes, especially runners, and also in non-athletes who suddenly increase their activity level. * Fascial defects: The protrusion of the muscle through the surrounding fascia leads to pain and swelling of the area. * Sciatic nerve entrapment syndrome: The sciatic nerve becomes entrapped by muscles or other structures. * Vascular
claudication Claudication is a medical term usually referring to impairment in walking, or pain, discomfort, numbness, or tiredness in the legs that occurs during walking or standing and is relieved by rest. The perceived level of pain from claudication can be ...
(secondary to atherosclerosis): The obstruction of arterial flow leads to muscular ischemia and causes pain in the buttock and calf. More common in the elderly with cardiovascular risk factors. *
Lumbar disc herniation Spinal disc herniation is an injury to the cushioning and connective tissue between vertebrae, usually caused by excessive strain or trauma to the spine. It may result in back pain, pain or sensation in different parts of the body, and physic ...
: A bulging disc or a herniated disc in the lower back which causes radiating pain from the buttock into the leg and sometimes into the foot.


Evaluation

PAES should be suspected in young healthy male patients with clinical symptoms consistent with compression of the vascular structures and without significant cardiovascular risk factors such as smoking. Multiple imaging modalities are used to confirm the diagnosis of PAES. Based on a systemic review by Sinha et al,
digital subtraction angiography Digital subtraction angiography (DSA) is a fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment. Images are produced using contrast medium by subtracting a "pre-contra ...
(DSA) is the most common imaging used for PAES diagnosis, followed by ankle–brachial index (18 percent),
computed tomography angiography Computed tomography angiography (also called CT angiography or CTA) is a computed tomography technique used for angiography—the visualization of arteries and veins—throughout the human body. Using contrast injected into the blood vessels, im ...
(CTA) (12 percent),
magnetic resonance angiography Magnetic resonance angiography (MRA) is a group of techniques based on magnetic resonance imaging (MRI) to image blood vessels. Magnetic resonance angiography is used to generate images of arteries (and less commonly veins) in order to evaluate t ...
(MRA) (12 percent),
duplex ultrasonography Doppler ultrasonography is medical ultrasonography that employs the Doppler effect to perform imaging of the movement of tissues and body fluids (usually blood), and their relative velocity to the probe. By calculating the frequency shift of a ...
(DU) (10 percent), exercise ankle-brachial index (4 percent), and other modalities (4 percent). According to a recent study by Willimas et al, a combination of DU and MRA is far superior in diagnosing PAES. Provocative maneuvers can be used to improve visualization of PAES on the imagines. The patient is initially positioned supine with the legs straight, and then instructed to forcefully plantar-flex. A plantarflexion force of 0 to 70 percent maximum has been shown to maximize the sensitivity and specificity for PAES diagnosis. The DU can be a quick, inexpensive, and noninvasive initial screening for PAES. Flow velocities in the popliteal artery will increase, as the popliteal artery is compressed, which is reflected on the DU. If DU is negative but there is still strong suspicion for PAES, MRA or CTA with provocative maneuvers are needed as follow-up imaging. MRA would demonstrate a focal occlusion or narrowing of the mid-popliteal artery, post-stenotic dilatation, or aneurysm of the distal popliteal artery. If MRA or CTA is non-conclusive, DSA may be used as a further option with a high sensitivity (> 97%) for PAES diagnosis. Additionally, functional PAES in which the gastrocnemius hypertrophy causes arterial compression during exercise can be best evaluated with dynamic CT. For dynamic CT, initial images are taken with the patient still. Further images are taken following a series of provocative maneuvers.


Management

* Asymptomatic patients: the management is typically expectant. PAES may be found incidentally on the imaging, but the patient may be symptom-free, thus, no intervention is required. * Symptomatic patients: open surgical decompression is the mainstay of treatment for PAES. The release of entrapment is achieved by performing division of the medial head of the gastrocnemius or musculotendinous band. The surgery can be performed with either posterior or medical approaches. Previous studies show a medial approach is beneficial for type I and II while a posterior approach is better for type III and IV. Additionally, the use of Botulinum Toxin A has been used as an alternative noninvasive treatment for functional PAES. A diagnosis of functional PAES is made if symptoms are improved after Botulinum injection. However, If symptoms are persisted, the patient can undergo an additional Botulinum injection or proceed with surgical decompression. The outcome following the surgery is usually favorable. Successful resolution of PAES occurs in 77 percent of cases. Surgical complications include deep vein thrombosis, hematoma, wound infection, or seroma. After the surgery, patient is usually monitored using arterial duplex ultrasonography 1, 3, 6, and 12 months, and annually after that.


Complications of untreated PAES

Early detection and management of PAES can lead to a favorable outcome. However, prolonged compression of popliteal artery can lead to extensive arterial damage and permanent claudication or limb loss.{{Cite journal , last1=Shahi , first1=Niti , last2=Arosemena , first2=Mariano , last3=Kwon , first3=Jeontaik , last4=Abai , first4=Babak , last5=Salvatore , first5=Dawn , last6=DiMuzio , first6=Paul , date=2019-08-01 , title=Functional Popliteal Artery Entrapment Syndrome: A Review of Diagnosis and Management , url=https://www.annalsofvascularsurgery.com/article/S0890-5096(19)30243-2/abstract , journal=Annals of Vascular Surgery , language=English , volume=59 , pages=259–267 , doi=10.1016/j.avsg.2018.12.105 , issn=0890-5096 , pmid=31028851, s2cid=135466438 Complications of PAES may include: * Distal arterial
thromboembolism Thrombosis (from Ancient Greek "clotting") is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platelets (thro ...
. * Popliteal artery
thrombosis Thrombosis (from Ancient Greek "clotting") is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platelets (thro ...
. * Popliteal artery
stenosis A stenosis (from Ancient Greek στενός, "narrow") is an abnormal narrowing in a blood vessel or other tubular organ or structure such as foramina and canals. It is also sometimes called a stricture (as in urethral stricture). ''Stricture'' ...
. * Limbs
amputation Amputation is the removal of a limb by trauma, medical illness, or surgery. As a surgical measure, it is used to control pain or a disease process in the affected limb, such as malignancy or gangrene. In some cases, it is carried out on indi ...
. Nonetheless, the course of PAES is often slow and takes time, thus, limbs loss is rarely seen, even in PAES patients.


References

Vascular surgery Syndromes