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Extensor Digiti Minimi Muscle Anatomy

The extensor digiti minimi (EDM), a fusiform slip of muscle, is a partially detached part of the extensor digitorum. It’s located in the posterior compartment of the forearm.

Extensor Digiti Minimi Muscle Anatomy

Extensor Digiti Minimi attached proximally by a common extensor tendon to the lateral epicondyle, the tendon of this extensor of the little finger runs through a separate compartment of the extensor retinaculum, posterior to the distal radio-ulnar joint, within the tendinous sheath of the extensor digiti minimi.

See Also: Forearm Muscles Anatomy & Function

The tendon then divides into two slips; the lateral one is joined to the tendon of the extensor digitorum, with all three tendons attaching to the dorsal digital expansion of the little finger. After exerting its traction primarily on the 5th digit, it contributes to extension of the hand.

See Also: Hand Anatomy, Bones & Muscles
Extensor Digiti Minimi Muscle

This muscle is innervated by the posterior interosseous nerve (C7, C8) a branch of the radial nerve.

Blood supply to this muscle comes from two sources: radial artery (via the radial recurrent artery) and ulnar artery (via the anterior and posterior interosseous arteries).

Extensor digiti minimi functions primarily to extend the fifth digit at its metacarpophalangeal joint.

OriginLateral epicondyle of humerus
InsertionExtensor expansion of 5th digit
InnervationPosterior interosseous nerve, the continuation of the deep branch of the radial nerve (C7, C8)
Blood SupplyInterosseous recurrent artery
ActionExtends 5th digit at metacarpophalangeal and interphalangeal joints

To test the extensor digiti minimi, the little finger is extended against resistance while holding digits 2–4 flexed at the metacarpophalangeal joints.

The extensor digiti minimi can be used to correct the abducted posture of the small finger in patients suffering from ulnar nerve dysfunction. In this procedure, the tendon is rerouted beneath the extensor digitorum communis tendon or junctura tendinae to the small finger and attached to the radial portion of the extensor hood. This adjustment addresses the muscle imbalance.

References & More

  1. Clinically Oriented Anatomy – 8th Edition
  2. Clinical Anatomy by Regions, Richard S. Snell.
  3. Tanaka T, Moran SL, Zhao C, Zobitz ME, An KN, Amadio PC. Anatomic variation of the 5th extensor tendon compartment and extensor digiti minimi tendon. Clin Anat. 2007 Aug;20(6):677-82. doi: 10.1002/ca.20480. PMID: 17352412. Pubmed
  4. Dellon AL. Extensor digiti minimi tendon transfer to correct abducted small finger in ulnar dysfunction. J Hand Surg Am. 1991 Sep;16(5):819-23. doi: 10.1016/s0363-5023(10)80142-x. PMID: 1658117. Pubmed
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