Obturator Artery

OBTURATORIA ARTERIA, VENA. The obturator artery (a. obturatoriae, closing-hole artery) exhibits great variability in its origin, position, course, and branching.

Fig. 1. Right obturator artery and inferior epigastric artery of a male: 1 - ductus deferens; 2 - Hesselbach's ligament; 3 - pubic branch; 4 - Gimbernat's ligament; 5 - pubic branch of the inferior epigastric artery; 6 - pubic branch of the obturator artery; 7 - urinary bladder; 8 - middle hemorrhoidal artery; 9 - internal pudendal artery; 10 - inferior gluteal artery; 11 - obturator artery; 12 - obturator nerve; 13 - external iliac vein; 14 - superior gluteal artery; 15 - iliolumbar artery; 16 - hypogastric artery; 17 - deep circumflex iliac artery; 18 - external iliac artery; 19 - testicular artery; 20 - common iliac artery; 21 - common iliac vein.

In approximately 70% of cases, it originates from the hypogastric artery (a. hypogastrica) and in 30% from the external iliac artery system (a. iliaca ext.). In the first group, the following variants of origin of the obturator artery are noted (Yashchinsky): from the trunk of the hypogastric artery in 3.2%, from its posterior primary branch in 19.1%, from the anterior primary branch in 41.4%, from a common trunk for the internal pudendal and inferior gluteal arteries in 5.2%, from the inferior gluteal artery in 3.2%, from the internal pudendal artery in 2.9%, and from small branches in 2.6%. The second group includes cases where the obturator artery arises either from the external iliac artery trunk (Fig. 1), from the inferior epigastric artery, or from the femoral artery; finally, cases of a double-root origin are observed, specifically with one root from the hypogastric artery system and the other from the external iliac artery system. In such cases, before entering the obturator canal, both arteries fuse, and their common trunk enters the canal.

Figure 2. Anomalous origin of the obturator artery: 1 - testicular artery; 2 - ductus deferens; 3 - Hesselbach's ligament; 4 - external spermatic artery; 5 - obturator artery; 6 - Gimbernat's ligament; 7 - inguinal aponeurotic falx; 8 - pubic branch of the inferior epigastric artery; 9 - pubic branch of the obturator artery; 10 - internal branch of the obturator artery; 11 - symphysis; 12 - urogenital trigonum; 13 - artery of the penis; 14 - inferior gluteal artery; 15 - obturator nerve; 16 - obturator artery (rudimentary); 17 - hypogastric artery; 18 - external iliac artery; 19 - iliolumbar artery; 20 - common iliac artery. Variants of the second group (arising from the external iliac artery system) are of particular practical importance due to the artery's relationship to the femoral ring. When dividing a hernia-constricting ring, especially using the old closed method, such proximity threatens profuse and sometimes fatal hemorrhage, which is why this variant was termed 'corona mortis' in the past. According to Yashchinsky's studies, among cases of this variant—which is more frequent on the right side and in women—the obturator artery arises most often from the inferior epigastric artery (28.5%), less frequently from the external iliac artery (1.2%) (Fig. 2), and even less frequently from the femoral artery (0.4%). Its relationship to a femoral hernia varies considerably depending on the specific variant in this group: if the obturator artery arises from the external iliac artery, it has no relation to the hernia; if it arises from the femoral artery, it passes behind the hernia; if it arises from the inferior epigastric artery, it lies either lateral to the hernia (if the obturator artery arises from the central part of the inferior epigastric artery) or medial to it (if the obturator artery branches off the inferior epigastric above the inguinal ligament); the latter is less common (Yashchinsky). The obturator artery may be completely absent, in which case it is replaced by branches of the femoral artery; or, alongside a well-developed one, an accessory obturator artery (a. obturatoriae accessoria) may exist, anastomosing with the branches of the main one. Covered by the peritoneum lining the pelvic wall down to the tendinous arch of the levator ani muscle, the obturator artery (as well as the obturator veins and nerve) runs forward and downward along the linea innominata of the lesser pelvis and, lying beneath the obturator nerve, enters the obturator canal, where it divides into its branches. This course and position of the artery occur when it arises from the hypogastric artery. Only in cases of its very high origin (above the 2nd sacral foramen) does it lie above the nerve, though before entering the canal it still passes beneath the nerve (Tikhomirov). When arising from the external iliac artery trunk, it approaches the obturator canal, lying medial to the external iliac vein and posterior and lateral to the femoral ring; when arising from the femoral artery, the obturator artery penetrates the femoral canal (anterior or posterior to the vein), then, bending over the horizontal ramus of the pubis, approaches the obturator canal, thus lying along the posterior circumference of the femoral ring; when originating from the epigastric artery, the obturator artery lies, as indicated, along either the outer or inner circumference of the femoral ring and thus reaches the obturator canal. The branches of the obturator artery—pubic branch, internal branch, posterior branch, and anterior branch—supply the iliopsoas, quadratus femoris, levator ani, obturator externus and internus, adductor magnus and minimus, brevis, longus, pectineus, and gracilis muscles, the ilium, symphysis, ischial tuberosity, the adipose tissue of the acetabulum, the head of the femur, lumbar lymph nodes, and the urinary bladder. Variants of the branching of the obturator artery relate mainly to the diversity of anastomoses between it and the inferior epigastric artery (and external iliac artery). The normally existing anastomosis between the pubic branch of both arteries, if significantly expressed, presents all those practically important features that occur when the obturator artery arises from the inferior epigastric artery. The obturator vein (v. obturatoriae), usually double, accompanies the corresponding artery, but in its patterns of termination it does not always follow the variants of the arterial origin. It most often drains into the hypogastric vein, but also broadly anastomoses with the external iliac vein and the medial femoral circumflex vein. It collects blood from the scrotum (or labia majora) and the adductor muscles of the thigh. Ligation of the obturator artery is possible within the pelvic cavity or from the anterior surface of the thigh. In the first case, the access is the same as for exposing the hypogastric artery. In the second case, a vertical incision is made downward from the middle of Poupart's ligament and the pectineus muscle is exposed. After dissecting it at the pubic bone, it is retracted medially or incised. Penetrating deeper, the fascia and muscle fibers of the obturator externus are divided transversely, thereby exposing the obturator vessels and nerve; the femoral vessels remain on the lateral side.