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Obturator Nerve

- Anatomy:
    - formed from anterior branches of L2, L3, L4 (see innervation of muscles of the lower limb)
    - largest nerve formed from anterior divisons of  lumbar plexus ;
    - roots unite within the posterior part of psoas, & then descends thru psoas & runs downward over sacral ala into lesser pelvis, lying 
           lateral to ureter & internal iliac vessels;
    - enters the upper part of the obturator foramen and then subsequently divides into anterior and posterior branches;

- Anterior Branch:
    - runs in front of obturator externus  & adductor brevis ;
    - it runs behind the   pectineus  and adductor longus muscles;
    - gives off articular twig that enters hip joint thru acetabular notch;
    - supplies muscular branches to hip adductors & then divides into cutaneous, vascular, and communicating vessels;

- Cutaneous Branch:
    - when present, it assists in innervation of skin and fascia over distal 2/3 of thigh;

- Posterior Branch:
    - pierces anterior part of obturator externus;
    - nerve then runs downward behind the adductor brevis & and in front of the adductor magnus;
    - it then splits into branches that are distributed to upper (adductor) part of adductor magnus  & sometimes to adductor brevis;

Obturator-nerve palsy resulting from intrapelvic extrusion of cement during total hip replacement. Report of four cases.