What is the anatomy of the obturator nerve in nerve entrapment syndromes of the lower extremity?

Updated: Oct 15, 2019
  • Author: Minoo Hadjari Hollis, MD; Chief Editor: Thomas M DeBerardino, MD  more...
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Answer

The obturator nerve is formed by the fusion of anterior branches of the anterior primary rami of L2, L3, and L4. The largest contribution is from L3, and the smallest contribution typically is from L2. The rami fuse in the substance of the psoas and emerge from the medial border of the psoas beneath the common iliac vessels just lateral to the sacrum.

The obturator nerve then travels along the lateral wall of the lesser pelvis to enter the obturator foramen. Just anterior to the internal obturator muscle and before entering the thigh, the nerve divides into an anterior branch and a posterior branch. The anterior branch travels superficial to the internal obturator muscle but deep to the pectineus and the adductor longus, then travels superficial to the adductor brevis.

The obturator nerve terminates at the distal aspect of the adductor longus, forming a subsartorial plexus by communicating with the anterior cutaneous branches of the femoral and saphenous nerves. The nerve then gives off its motor branches to the muscles and extends its articular branches to the hip joint. The motor branches arise distal to the obturator foramen to supply the adductor brevis, adductor longus, and gracilis.

Rarely, a terminal cutaneous branch may emerge from the inferior aspect of the adductor longus and follow the medial border of the sartorius to the medial knee region, where it supplies the skin of the medial and distal thigh region.


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