This section is from the book "Anatomy Of The Arteries Of The Human Body", by John Hatch Power. Also available from Amazon: Anatomy of the Arteries of the Human Body, with the Descriptive Anatomy of the Heart.
The obturator artery not unfrequently comes off from the epigastric; and fig. 46, on page 293, represents three different routes which it may take, in order to arrive at the obturator foramen. First, it may arise from the internal iliac, and accompany the obturator nerve; this is its usual origin and course. Secondly, it may arise from the epigastric, and descend, without crossing the femoral ring, towards the obturator foramen. Thirdly, it may arise from the epigastric, and get to the inside of the ring, by running along its anterior margin, i.e. along Poupart's ligament. These two last varieties are marked G, G, in the figure. It may arise from the epigastric and pass obliquely along the horizontal ramus of the pubis internally, and then dip into the obturator foramen.
It is evident, that it is only when the irregular obturator passes along the back of Poupart's ligament, and coasts along the internal margin of the femoral ring in order to reach the obturator foramen, that it can be endangered in the operations for the relief of strangulated femoral hernia. This peculiarity in its course was first pointed out by Mr. Wardrop, who relates two cases of this kind, one seen by himself and Dr. Barclay, in Edinburgh; and another by himself, in Paris.*
The obturator artery may also arise from the external iliac, or from the femoral, or by a double root from the internal iliac and obturator. Green relates a case in which it was wanting on one side, and its place supplied by branches of the profunda. The preparation is in the late Dr. M'Cartney's museum.