Historical Background

Popliteal artery entrapment is a congenital anomaly in which the popliteal artery passes medial to and beneath the medial head of the gastrocnemius muscle or a slip of that muscle, with consequent compression or functional occlusion of the artery. Popliteal artery entrapment was first noted in 1879 by Stuart, an Edinburgh medical student, who described an anatomic variant of the popliteal artery dissected from a gangrenous limb. The significance of this anomaly was not recognized until 1959, when Hamming at the University of Leyden reported a case of a 12-year-old boy with claudication and thrombosis of the popliteal artery with the same anatomic abnormality as initially described by Stuart. Treatment included thrombectomy with division of the gastrocnemius muscle. In 1962 Servello at the University of Padua described the case of a 28-year-old farmer who had an 8-year history of leg pain, medial displacement of the popliteal artery, and a small popliteal aneurysm. The medial head of the gastrocnemius muscle was divided, and an aneurysmorrhaphy performed. In 1965 Love and Whelan described this anatomic variant as a cause of calf claudication in two young adults in the U.S. military.

The incidence of popliteal artery entrapment ranges from 0.17% in a review of 20,000 asymptomatic Greek soldiers to 3.5% in a study of autopsy specimens, suggesting that most cases are asymptomatic. The concomitant entrapment of the popliteal vein with the artery has been reported in only 7.6% of cases. Popliteal artery entrapment is more common in males and more than half the cases have been reported in patients younger than 30 years of age. The anatomic variant causing the entrapment occurs bilaterally in up to two thirds of cases, although it may be asymptomatic in the contralateral limb.

Preoperative Preparation

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  The diagnosis of popliteal artery entrapment should be considered in any young adult with calf claudication, especially in the absence of atherosclerotic risk factors.

  
  
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  The diagnosis of popliteal artery entrapment is confirmed by demonstrating a decrease in the ankle-brachial index and elevated popliteal artery velocities on duplex scanning in association with active plantar flexion of the ankle with the knee in full extension. There is a high rate of false-positive results, especially in athletes.

  
  
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  Computed tomography or magnetic resonance imaging displays both the vascular abnormality and the musculotendinous variation, as well as other pathology that may mimic entrapment syndrome, such as an adventitial cyst.

  
  
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  Conventional angiography should confirm medial displacement of the popliteal artery and extrinsic compression on active plantar flexion of the ankle. In up to 50% of patients, occlusion of the popliteal artery may be present. Irregularity of the wall of the popliteal artery in an otherwise normal arterial tree may also be observed, along with prestenotic or poststenotic dilatation.

  
  
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  Six variants of popliteal artery entrapment have been described that are related to variations in the embryologic development of the gastrocnemius muscle ( Fig. 47-1 ). In type I and type II entrapment the artery is displaced medially. In type I the gastrocnemius muscle is normally situated, whereas in type II the medial head of the gastrocnemius muscle has a variable attachment on the lateral aspect of the medial femoral condyle or intercondylar area. In type III entrapment a portion of the gastrocnemius muscle remains posterior to the artery, leaving an abnormal slip or band compressing the artery. Type IV entrapment describes a scenario in which the popliteal artery is situated deep to the popliteus muscle or fibrous bands. Type V entrapment can involve any of the previously mentioned abnormalities but also involves both the popliteal artery and the popliteal vein. Type VI entrapment is a functional form of entrapment without clear anatomic abnormality. This condition, termed physiologic popliteal artery entrapment syndrome, may be seen in high-performance athletes because of a hypertrophied gastrocnemius, soleus, plantaris, or semimembranosus muscle that causes vascular compression. It may be confused with chronic recurrent exertional compartment syndrome that can occur in the same population.

  
  

  
  

  
  

  

  
  

  
  

  Types of popliteal artery entrapment syndrome.

  
  

  (From Pillal J: A current interpretation of popliteal vascular entrapment, J Vasc Surg 48:61S-65S, 2008, Fig. 1.)

  
  

Pitfalls and Danger Points

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  Exposure of the popliteal artery. Most vascular surgeons are more familiar with the medial approach to the popliteal artery than with the direct, or posterior, approach. Nonetheless, the posterior approach to the popliteal fossa provides excellent visualization of the anatomic abnormalities but can be limited if a bypass onto the tibioperoneal trunk or selected tibial vessels is required. The posterior approach to a patient with popliteal artery entrapment is preferably used in types III to VI, with standard medial exposure reserved for type I and type II entrapment.

  
  
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  Accessibility of a venous conduit. Although the small saphenous vein is readily accessible via the posterior approach, it may be unsuitable for use based on caliber or quality. If the cephalad portion of the S-shaped incision for the posterior approach is extended along the medial aspect of the thigh, the great saphenous vein is accessible. Nonetheless, it can be awkward to harvest the great saphenous vein in the prone position.