Teaching Case

Rapidly progressive unilateral lower limb intermittent claudication with diminished walking distance and unilateral coldness and numbness, on clinical exam dorsalis pedis pulse was not detected.

CT revealed the abnormal relation between the popliteal artery and the medial head gastrocnemius on both sides where the arteries are seen deviated medially wrapping around the muscle rather than following the usual lateral course. This abnormal relation resulted in compression of both arteries with subsequent total occlusion of the left artery and only gentle extrinsic compression on the right artery.

The popliteal artery may be entrapped by the related anatomical structures at the popliteal fossa especially the medial head gastrocnemius muscle, popliteus muscle or less commonly anomalous traversing fibrous bands [1]. And although the anatomical entrapment is existing in nearly 3% of the population, yet, the symptomatic entrapment occurs in the minority of cases notably those with well-developed muscles which explain why this syndrome is more common in athletic young males [2].

Patients will be presented with intermittent claudication, and on examination, they will reveal deterioration of the leg arterial flow on plantar flexion which exaggerates the extrinsic arterial compression, the chronic arterial compression will result in intimal hyperplasia and progressive arterial stenosis which may result finally in total gradual permanent arterial occlusion or may result in acute thrombosis with limb-threatening ischaemia.

Popliteal entrapment syndrome is moreover anatomically classified into five different types according to the mechanism of entrapment [3].

Type I: Entrapment due to an excessive medial course of the popliteal artery being medial to medial head gastrocnemius.
Type II: Entrapment due to an excessive lateral origin of the medial head gastrocnemius and subsequently an artery with a standard course will be medial to the muscle.
Type III: Entrapment by an accessory slip of gastrocnemius crossing over the artery.
Type IV: Entrapment of the artery by being deep to popliteus muscle.
Type V: Entrapment of both popliteal artery and vein.

CT angiography and MRI are the best modalities to reveal the anatomical entrapment and the possible related complications while Doppler can demonstrate the drop of the arterial flow distal to the popliteal artery on planter flexion as manifested by increased peak systolic velocity and the diminished diastolic component of the flow [1, 2].

Acute total arterial thrombosis due to entrapment is managed by bypass surgery while intermittent arterial occlusion can be treated by surgical arterial release [2].