The obturator membrane is a tough fibrous sheet that almost completely closes the obturator foramen, the largest opening in the skeleton. It attaches to the bony margins of the foramen except at the supero-lateral corner where the obturator canal permits passage of the obturator nerve, artery, and vein. The obturator internus muscle arises from the pelvic (inner) surface of the membrane; the obturator externus arises from the perineal (outer) surface.
Closes the obturator foramen to provide a surface for obturator muscle origin and to prevent herniation of pelvic contents through the foramen, while permitting passage of the obturator neurovascular bundle through the obturator canal.
The obturator membrane is disrupted in obturator hernia, which most commonly affects elderly thin women. Obturator hernias pass through the obturator canal above the membrane and present with intestinal obstruction and the Howship-Romberg sign. The obturator membrane is accessed in ilioinquinal and transinguinal approaches to the acetabulum for fracture fixation. In hip arthroplasty, the obturator membrane provides an orientation landmark for cup anteversion and abduction angle assessment on intraoperative fluoroscopy.
Obturator hernia passes through the obturator canal above the membrane, producing intestinal obstruction with the Howship-Romberg sign of medial thigh pain on hip extension in an elderly thin woman; CT confirms the hernia sac at the obturator foramen and emergency surgery prevents strangulation.
