Popliteal artery entrapment syndrome: morphological classification utilizing MR imaging

Objective: To retrospectively analyze magnetic resonance (MR) findings in patients with popliteal arterial entrapment syndrome. Materials and methods: This study was a retrospective MRI and CT scan review of 12 patients with 23 limbs with popliteal artery entrapment syndrome (PAES) treated over a 10-yr period. All 12 patients (23 limbs) were evaluated with MR and CT scan (11 patients-bilateral sides; one patient-unilateral side). All cases were classified as to various types of anomalous relationships between the popliteal artery and the neighboring muscles. The PAES was classified to gastrocnemius medial head and lateral head anomaly. Gastrocnemius medial head anomaly was classified according to the classification made by Whelan and Rich, from type 1 to type 6 [12, 13]. Gastrocnemius lateral head anomaly was defined as popliteal artery entrapment due to medially inserted gastrocnemius lateral head or aberrant accessory head of gastrocnemius lateral head. Results: The gastrocnemius medial head anomaly was found in 14 limbs (14/23). The classic type 1 was found in none, type 2 in five patients (six limbs), type 3 in four patients (five limbs), type 4 in none, type 5 in one patient (one limb) and type 6 in one patient (two limbs). The uncommon type, i.e. lateral head of gastrocnemius anomaly, was found in five patients (eight limbs). Conclusion: The gastrocnemius medial head anomaly was the cause of PAES, and PAES was classified by medial head anomaly. However the gastrocnemius lateral head anomaly was also the cause of PAES, and most cases of gastrocnemius lateral head anomaliy showed aberrant accessory slip which entrapped the popliteal artery and vein.