Obturator foramen

The obturator foramen (Latin foramen obturatum) is the large opening created by the ischium and pubis bones of the pelvis through which nerves and blood vessels pass.

Structure

It is bounded by a thin, uneven margin, to which a strong membrane is attached, and presents, superiorly, a deep groove, the obturator groove, which runs from the pelvis obliquely medialward and downward.

This groove is converted into the obturator canal by a ligamentous band, a specialized part of the obturator membrane, attached to two tubercles:

Variation

Reflecting the overall sex differences between male and female pelvises, the obturator foramina are oval in the male and wider and more triangular in the female.

Additionally, unilateral pelvis hypoplasia can cause differences in size between the obturator foramina, and there are even rare reports of individual pelvises featuring a double obturator foramen in one of the hip bones.