Popliteal Artery Entrapment Syndrome
Popliteal artery entrapment syndrome is an infrequent but serious cause of disability in young adults, typically affecting athletic individuals. The syndrome results when there is compression of the popliteal artery by the medial head of the gastrocnemius muscle. Although it is typically difficult to diagnose, arteriography can be a useful tool in demonstrating this anomaly. Clinicians should strive to detect this syndrome at an early stage so that surgical treatment is minimized and vascular reconstruction is avoided.
Popliteal artery entrapment syndrome, which results in claudication and chronic leg ischemia, is a relatively uncommon pathology in young adults. The popliteal artery may be compressed behind the knee due to a congenital deformity of the muscle or tendon insertions. Repetitive trauma to this area may result in stenotic artery degeneration, com?plete artery occlusion, or formation of an aneurysm.1
Popliteal artery entrapment syndrome was first described in 1879 by Anderson Stuart, a medical student.2 During an an?atomic dissection in a 64-year-old man, Stuart noted an abnormal course of the popliteal artery lateral to the medial head of the gastrocnemius muscle. In 1959, Hamming first described the management of popliteal artery syndrome in a 12-year-old patient who was treated with myotomy of the medial head of the gastrocnemius muscle and concomitant endarterectomy of the popliteal artery.3 Hamming and Vink later reported four more cases and estimated a 40% incidence of popliteal artery entrapment syndrome with claudication in patients younger than 30 years.4 Servello was the first to draw attention to diminished distal pulses observed with forced plantar or dorsiflexion in patients with this syndrome.5 In 1981, Bouhoutsos and Daskalakis reported 45 cases in a population of 20,000 Greek soldiers.6 The increasing frequency with which pop?liteal artery entrapment is being reported strongly suggests a greater awareness of the syndrome.7,8
Love and Whelan proposed classifying this pathology into four types based on the various relationships between the popliteal artery and the muscles of the popliteal space.9 Rich and Hughes de?scribed popliteal vein compression, there?by adding a fifth type into the former classification.10 The functional type of the popliteal vessel compression was first described by Rignault and colleagues in 1985 and labeled by Levien as type VI popliteal vessels entrapment syndrome (Table).8-11
A 34-year-old woman presented with numbness and intermittent claudication of the left leg after walking a distance of 150 m. The symptoms were aggravated when she wore high-heeled shoes. She had no history of hypertension, hyperlipidemia, smoking, or thrombophilia. Clinical examination disclosed normal peripheral leg pulses at rest and weakened peripheral leg pulses in the symptomatic limb after plantar flexion. Doppler ultrasonography revealed normal bilateral ankle-brachial arterial in?dices when her feet were in a neutral position. After forced plantar and dorsi flexion, however, the arterial signals were diminished and the arterial index drop?ped to 0.3 at the left leg. Magnetic resonance angiography (MRA) demonstrated extrinsic compression of the left pop?liteal artery when the foot was in a neutral position, with restoration of peripheral arterial flow. There was no popliteal artery blood flow during forced active plantar flexion of the foot against resistance (Figure 1).
The treatment of the pathology in?cluded popliteal space surgery. The patient underwent an S-shaped skin incision, through which a posterior approach to the popliteal region was attained. Using this approach, identification of any possible abnormalities in the course of the popliteal vessels is easier and the relationships with the adjacent structures of the popliteal fossa are more apparent. The lateral course and the insertion of the medial head of the gastrocnemius muscle were identified and brought to the surface with a medial deviation of the pop?liteal artery far from the popliteal vein. This case was identified as type II popliteal artery entrapment syndrome (Figure 2). The medial head of the gastrocnemius muscle was divided (myotomy) and the artery showed no macroscopic degenerated damage (Figures 3 and 4).
The patient's recovery was uneventful and she was discharged from the hospital on postoperative day 2. At 6-month follow-up, the patient reported no symptoms of popliteal artery entrapment and the peripheral Doppler ultrasonography signals at plantar and dorsiflexion of the foot appeared normal.
Popliteal artery entrapment syndrome is characterized by extrinsic compression of the popliteal artery, which causes a variety of symptoms after strenuous exercise. Currently, two types of this anomaly are recognized according to pathogenesis: the congenital or classical-anatomical type and the functional type. The congenital type is thought to occur as a result of anomalies during popliteal artery formation. Compression in the functional type is the result of contraction of the medial head of the gastrocnemius muscle in tandem with the plantaris muscle, which displaces the neurovascular bundle laterally against the external femoral condyle and the canal of the soleus muscle. Venous compression may result from perivascular fibrous tissue formation and abnormalities within the medial head of the gastrocnemius muscle.
Diagnosis of the syndrome should be considered in every young person presenting with intermittent claudication. There is pain in the calf and the limbs, which may be reproduced only when the person is walking and not when they are running. Standing on tips of toes may also be painful. Some women experience pain when wearing high-heeled shoes, as in the case of our patient. Paresthesias and occasional limb fatigue may be the only symptoms, especially in functional cases.
Signs of acute ischemia are present when acute thrombosis occurs, but may be absent when good collateral inflow from the genicular branches develops. Reduction or absence of pedal pulses during dorsiflexion helps diagnose this condition.8 Use of Doppler ultrasonography and duplex mapping, which detect alterations in the three-phase pulse pattern and allow dynamic visualization of the popliteal artery during maneuvers, also help establish a diagnosis. It seems that the detection of compression of the popliteal artery during positional maneuvers, however, is not enough for diagnosing this syndrome. The duplex scan is also a highly operative-dependent study. Arteriography is an invasive study that helps in the differential diagnosis from other conditions, such as popliteal artery cystic disease and compartment syndromes, where no compression of the popliteal artery is detected. It also helps determine the type of compression (types I and II demonstrate medial deviation of the popliteal artery, whereas, in the functional type, lateral displacement is the rule) and provides information about the distal vascular bed in case arterial reconstruction is considered. MRA is an alternative noninvasive technique that provides anatomical information about the popliteal fossa. MRA has proved ex?tremely useful in detecting vascular complications of the syndrome, such as aneurysm formation.12
Treatment is indicated in all cases of anatomical entrapment. Most authors prefer the posterior "S" approach, which offers the advantage of more accurate detection and correction of the identified anomalies. The medial approach offers the advantage of saphenous vein harvesting when femoropopliteal bypass is re?quired because of artery occlusion.
Clinicians should strive to diagnose popliteal artery entrapment syndrome at an early stage in symptomatic patients, before permanent arterial lesions occur, thereby limiting surgical treatment to a simple myotomy and avoiding vascular reconstruction. The syndrome should be considered in the differential diagnosis of any patient younger than 50 years who presents with calf and foot claudication symptoms during exercise, particularly in athletic individuals without athero?scler?otic risk factors. MRA is a noninvasive method that can confirm popliteal artery compression with the foot at functional positions.
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