Introduction

Popliteal artery entrapment syndrome (PAES) is a rare vascular condition, seen in only 3.5% of cases at post-mortem [1]. It is a developmental anomaly which occurs due to abnormal relationship between popliteal artery and the myofascial structures in the popliteal fossa [2]. Patients with PAES have varied presentation; they may be asymptomatic, may have features of arterial insufficiency, and may present as popliteal artery aneurysm with or without features of distal embolization [3]. Diagnosis of PAES always remains challenging due to its atypical presentation. We hereby report a case of PAES, which was initially mis-diagnosed as a peripheral vascular disease for almost a period of three years, until patient was reported and diagnosed at our center.

Case Report

A 28-year-old gentleman, chronic smoker, reported to a peripheral surgical center with complaints of progressive claudication right leg of one month duration. Pain used to start in calf muscles after walking 100 m and used to subside completely after taking rest. Patient was initially diagnosed and treated as a case of early onset peripheral vascular disease. He was advised smoking cessation and started on antiplatelet, statin, and phosphor-di-esterase-3 inhibitor. Despite on medication, patient noticed decrease in painful-walking distance (PFWD) to 40–50 m over next two years. In view of persistent and worsening symptoms, patient reported to the intervention radiologist; an arterial color Doppler was carried out, which revealed significant stenosis of right popliteal artery, for which he underwent popliteal artery angioplasty. Patient symptoms did not improve with angioplasty and condition further worsened over next one year hence, reported to vascular center for the first time with complaints of disabling claudication right leg (PFWD of 20–25 m) which was hampering his day-to-day activities. On examination, popliteal and distal pulses were absent in right leg, whereas left leg pulses were normal. Ankle Brachial Index (ABI) of the right and left limbs was 0.54 and 0.98 respectively. CT angiogram of lower limbs revealed complete occlusion of right popliteal artery (P2 segment) and existence of an accessory muscle sling, arising from medial head of gastrocnemius, causing external compression over the popliteal artery (Fig. 1). MRI of the right lower limb further confirmed type-III PAES with popliteal artery occlusion (Fig. 2). In view of occluded popliteal artery with external compression by the muscle sling, a surgical bypass was considered. P1 to P3 segment popliteal artery bypass was done by medial approach using reverse saphenous vein graft (RSVG) harvested from the ipsilateral thigh (Fig. 3). In post-operative period, patient was kept on injectable anti-coagulation (Inj Lower Molecular Weight Heparin 1 mg/kg body weight, subcutaneous, twice a day), broad spectrum antibiotics, analgesics, and supportive care. Ambulation started after 24 h, thigh and leg drains were removed on 3rd and 4th day respectively, and patient was discharged on 10th post-operative day on oral anticoagulation with palpable distal pulses and patent GSV graft on Doppler ultrasound. Patient was continued on low dose oral anticoagulation (Apixaban 2.5 mg twice a day) and single antiplatelet drug for six months which were discontinued thereafter. Post surgery, patient had significant improvement in his symptoms. At present, after one year of surgery, he can walk up to 5–6 km and climb stairs without pain, he has palpable distal pulses (DPA/PTA) and has an Ankle Brachial Index (ABI) of 0.94 in operated limb (equal to contralateral normal limb). Follow-up CT angiography shows a patent vein graft (Fig. 4).

Fig. 1
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Pre-op CT angio bilateral lower limbs (reconstructed posterior view) shows occluded right popliteal artery (P2 segment) and patent left popliteal artery

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Fig. 2
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MRI right leg – coronal view. a Medial head of gastrocnemius; b Lateral head of gastrocnemius; c Fascial sling arising from medial head; d Occluded popliteal artery

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Fig. 3
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a GSV harvested from ipsilateral thigh; b Proximal (P1) and distal (P3) popliteal artery exposure; c Tunneller in subfacial plain for transferring vein graft from supra-genicular (P1) inflow segment to infra-genicular (P3) outflow segment; d Proximal anastomosis between popliteal artery (P1 segment and proximal end of reverse saphenous vein graft; e Distal anastomosis between distal end of reverse saphenous vein graft and popliteal artery (P3 segment); f Wound closure thigh (vein harvest site], supra-genicular, and infra-genicular for vascular reconstruction with closed drainage tubes in situ

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Fig. 4
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Post-operative CT angio (bilateral lower limbs): Patent reverse saphenous vein graft (RSVG) between P1 and P3 popliteal segment on the right side

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Discussion

Popliteal artery entrapment syndrome (PAES) occurs due to abnormal relationships between myofascial structures and the corresponding popliteal artery in popliteal fossa and is classified into six types (Table 1). In our case, it was type III, in which a sling of fibrotic band, which was arising from medial head of gastrocnemius, was compressing on the right popliteal artery. The compression on popliteal artery results in various limb symptoms, (Table 2). Patient in reported case had class 3 symptoms, as his claudication distance was less than 100 m. PAES is most commonly seen in young and active males [1] and the most common symptom includes pain in the calf following exercise which gets relieved after taking rest [2]. Clinically, there can be absent or reduced popliteal and distal leg pulses, especially while performing a forced dorsi-flexion of foot. Our patient had absent popliteal and distal pulses, due to complete occlusion of popliteal artery. In PAES, Doppler ultrasound (DUS) can help in visualizing hemodynamic changes occurring due to external compression especially with dynamic ankle maneuvers [4]. Magnetic resonance imaging (MRI) has stood the test of time and is proven to be the investigation of choice to evaluate the anatomy of the popliteal fossa and understanding the relationship between the popliteal artery and its surrounding structures [5]. CT angiography or conventional angiography can detect compression/occlusion/ aneurysm. In our case, CT angiography revealed popliteal artery occlusion with external compression, which got further confirmed by MRI. Angioplasty or endovascular treatment remains ineffective in PAES, as it does not correct external compression, and hence surgery is considered as treatment of choice [6]. If the disease is diagnosed early with patent popliteal artery, a simple open surgical exploration with fasciotomy, myotomy, or fibrous band excision and release of external arterial compression is sufficient. If the patient has intimal injury with stenosis of popliteal artery, thrombo-endarterectomy with a venous patch repair remains a viable therapeutic option [2], but, if the patient has complete occlusion of popliteal artery, exclusion of occluded segment by using vein bypass is essential. In the reported case, we bypassed the occluded popliteal segment, using reverse saphenous vein graft. The outcome is good after surgical treatment, as we saw in our case. If it remains undiagnosed or mis-diagnosed, it always remains a threat to the limb.

Table 1 Heidelberg Classification of PAES
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Table 2 Classification of PAES based on severity of symptoms
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Conclusion

Popliteal artery entrapment syndrome is a rare vascular condition. Its diagnosis is difficult due to varied presentation and overlapping symptoms with other common vascular conditions. It requires a high index of suspicion for the diagnosis and warrants an early treatment to prevent limb complications. In the reported case, patient was initially mis-diagnosed as early onset peripheral arterial occlusive disease, and was in-appropriately treated with angioplasty without identifying and relieving external compression to the artery. After patient reported to our center, PAES was suspected clinically, confirmed on imaging and was successfully treated with surgical bypass resulting in favorable outcome.