Persistent Sciatic Artery: A Favorable Anatomic Variant in a Setting of Trauma

Abstract

Background: Persistent sciatic artery (PSA) is a rare congenital anomaly of the circulation of the lower limb that results from the persistence of an artery that normally regresses early in embryonic development. PSA is usually an incidental finding and is exceedingly rare to find bilaterally.

Case report: We present the case of a rare presentation of PSA that resulted in a favorable outcome for a patient who sustained a gunshot wound to his midthigh and discuss the history, embryology, anatomy, classification schema, imaging evaluation, complications, diagnosis, and management of PSA.

Conclusion: PSAs are of doubtful clinical significance when found incidentally at imaging; however, individual patient symptoms, unique arterial anatomy, and the PSA classification best determine the appropriate treatment options.

Keywords: Congenital abnormalities; femoral artery; lower extremity; persistent sciatic artery.

Figure 1.

Axial computed tomography angiography images show (A) the level of the takeoff of the inferior mesenteric artery from the aorta; (B) normal bifurcation of the aorta into the common iliac arteries; and (C) the level of the internal and external iliac arteries. The internal iliac arteries are prominent but not aneurysmal.

Figure 2.

Axial computed tomography angiography image shows arterial anatomy with trifurcation of the femoral artery and prominence of a persistent sciatic artery just distal to the obturator foramen.

Figure 3.

Axial computed tomography angiography image shows arterial anatomy in the midthigh with a bullet in the left medial thigh at the normal anatomic position of the femoral artery.

Figure 4.

Axial computed tomography angiography images show (A) arterial anatomy at the popliteal that originates from the anomalous posterior circulation (the posterior persistent sciatic artery) bilaterally and (B) arterial anatomy at the distal popliteal with normal 3-vessel runoff into the anterior tibial, posterior tibial, and peroneal arteries.

Figure 5.

Three-dimensional reconstructed anatomic views from the front (A) and posterior-right (B) of the patient show the persistent sciatic artery (Type 2a) as it supplies the dominant circulation of the lower extremities. There is normal appearing 3-vessel runoff distally. Note that the bullet (with metallic artifact in the mid left thigh) overlies the expected position of the femoral artery that appears atrophic and does not connect to the popliteal. There is no evidence of acute arterial bleed.

Figure 6.

The persistent sciatic artery (PSA) classification describes 5 types of variant anatomy. Type 1 is a complete PSA with a normal femoral artery. Type 2 is a complete PSA with incomplete femoral artery development. In type 2a, the femoral artery is present but terminates in the midthigh. In type 2b, the femoral artery is completely absent. Type 3 is an incomplete PSA in which only the proximal part of the sciatic artery is present, and the femoral arteries are fully developed. Type 4 is incomplete PSA in which only the distal part of the artery is present, and the femoral arteries are fully developed. Type 5 PSA originates from the median sacral artery. Type 5a has a developed femoral artery, and 5b has an underdeveloped femoral artery.