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Journal of the Anatomical Society of India

Variation in the distribution of the posterior interosseous nerve - A Case Report

Author(s): Rao, T.R. & Madhyastha, S.

Vol. 50, No. 1 (2001-01 - 2001-06)

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A rare case of unusual course and distribution of posterior interosseous nerve was found during dissection on the left side. The nerve from the dorsum of the hand showed further course towards the junction between the middle finger and index finger almost up to the distal end of the middle phalanx. Key words : Radial nerve, Posterior interosseous nerve.

Introduction :

The posterior interosseous nerve arises from the radial nerve in front of the lateral epicondyle of the humerus in the cubital fossa. It pierces the supinator, winds around the lateral aspect of the neck of radius in the substance of the muscle, to reach the posterior compartment of the forearm. After emerging from the supinator the nerve gives three short branches to extensor digitorum, extensor digiti minimi and extensor carpi ulnaris; two long branches - the medial branch supplies the extensor pollicis longus, the extensor indicis and the lateral branch supplies the abductor pollicis longus and extensor pollicis brevis. The nerve lies at first between the superfical and deep muscles of the back of the forearm along with posterior interosseous artery. But at the distal border of extensor pollicis brevis, it passes deep to the extensor pollicis longus and is diminished to a fine thread, it runs down on the dorsal aspect of the interosseous membrane with the anterior interosseous artery. It reaches the dorsum of the hand by passing through the fourth compartment of the extensor retinaculum. On the dorsum of hand it terminates in a pseudoganglion, from which branches are given off to distal radioulnar joint, wrist joint, intercarpal and carpometacarpal joints. (Anson, 1953; Williams et. at, 1995)

Observation :

The posterior interosseous nerve showed normal origin, course and distribution in the forearm but on reaching the dorsum of the carpus it showed slight thickening in its wall (pseudoganglion), from which filaments were distributed to the ligaments and articulation of the carpus. From the pseudoganglion the nerve showed further course towards the junction between the index and middle finger (2nd web space), where it branched to supply the adjacent aspect of middle and index finger almost up to the distal end of middle phalanx to supply the overlying skin. The remaining cutaneous innervation was normal. However such variation was not found in the opposite limb.

Discussion :

The posterior interosseous nerve may supply the anconeus, extensor carpi radialis brevis (36% of cases) and the opposed surfaces of the middle and index fingers (Bergman et al. 1988) When the superficial branch of radial nerve is absent completely its distribution on the hand is taken over by the musculocutaneous nerve (Hollinshead 1966).

References :

  1. Anson, B. J : Morris Human Auatomy In: The Nervous System. Francs, C. C; & voneida, I. J. Edr. 12th Edu Mc Graw Hill Book Co. New York : p 1069. (1953)
  2. Bergman, R. A; Thomson,S. A. et al : Compendium of Ahatomic Variation In : Nervous system, Urban & Schwarzenber, Baltimore : p 142 (1988).
  3. Hollinshead, W. H: Anatomy for Surgeons In : The Back & limbs Vol. 3. 1st Edn. Harper & Row. New York. : p 443. (1966).
  4. Williams, P. L. Bennister, L. H; Berry, M, et al : Gray’s Anatomy In : Nervous system. 38th Edn. Churchill Livingestone Edinburg : p. 1274 (1995).

J. Anat. Soc. India 50(1) 46 (2001) Opp. 46 Posterior Interosseous Nerve

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Fig.1. A - Posterior interosseous nerve B - Superficial branch of radial nerve

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