Joints and ligaments · Lower limb
Obturator membrane !
The obturator membrane is a tough sheet that closes most of the large hole in the lower hip bone, leaving a small canal for a nerve.
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What it is
A tough sheet covering most of the obturator foramen, the large hole in the lower hip bone.
What it does
Anchors the obturator muscles. A small gap at the top lets the obturator nerve and vessels pass to the thigh.
Key facts
- Where
- Closes obturator foramen except the obturator canal above
- Attaches
- Margins of obturator foramen
- Function
- Origin for obturator internus and externus; obturator canal passes obturator nerve and vessels
Relations
- Medial
- Pelvic surface: obturator internus and its fascia; the obturator nerve and vessels run along the pelvic side wall to the canal
- Lateral
- Outer surface: obturator externus, covered in front by pectineus and adductor brevis
- Above
- Obturator canal, between the membrane's upper edge and the obturator groove of the pubis
- Contents
- Through the canal: obturator nerve (dividing into anterior and posterior branches around this point), obturator artery and obturator vein
How to find it
Not palpable. In dissection it is reached from inside the pelvis by lifting off obturator internus, or from the thigh deep to pectineus and the adductors, where the canal is the gap at its upper edge.
On imaging
Pelvic CT shows an obturator hernia as a loop of bowel or fat between pectineus and obturator externus, at the level of the obturator canal. On ultrasound the obturator nerve branches are followed between the adductors below the canal.
Clinical notes
- Obturator nerve injury in pelvic surgery (lymph node dissection), pelvic fractures or childbirth weakens hip adduction and numbs a patch of the inner thigh
- Obturator nerve block near the canal prevents the adductor jerk during transurethral bladder surgery and helps in hip pain
- Pelvic disease on the side wall (for example ovarian) can irritate the obturator nerve and refer pain to the inner thigh
Anatomical variants
- The obturator artery may arise from the inferior epigastric artery and cross the superior pubic ramus (part of the corona mortis), at risk in pelvic and hernia surgery
- An accessory obturator nerve passing over the superior pubic ramus instead of through the canal is present in some people
Test yourself
Think of the answer, then tap the question to see it.
What passes through the obturator canal at the upper edge of the obturator membrane?
The obturator nerve, artery and vein, from the pelvis to the medial thigh.
What is the classic presentation of an obturator hernia?
A thin, elderly woman with small-bowel obstruction and pain down the inner thigh to the knee (Howship–Romberg sign).
Which muscles arise from the two surfaces of the obturator membrane?
The obturator internus from its pelvic surface and the obturator externus from its outer surface.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- membrana obturatoria TA2 1848
- Official Spanish (DeCS)
- Membrana obturatriz
- English (TA2)
- Obturator membrane
- Also called
- membrana obturans
Related
Sources: Terminologia Anatomica (TA2); Anatomy, Abdomen and Pelvis, Obturator Muscles.
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Representative model, for educational purposes only.
