Extensor expansion

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Extensor expansion
Tendons of forefinger and vincula tendina. (Extensor expansion not labeled, but region is visible.)
Anatomical terminology

An extensor expansion (dorsal expansion, dorsal hood, dorsal aponeurosis[citation needed]) is the special connective attachments by which the extensor tendons insert into the phalanges.

These flattened tendons (aponeurosis) of extensor muscles span the proximal and middle phalanges.[1]

At the distal end of the metacarpal, the extensor tendon will expand to form a hood, which covers the back and sides of the head of the metacarpal and the proximal phalanx.


The expansion soon divides into three bands:

  • lateral bands pass on either side of the proximal phalanx and stretch all the way to the distal phalanx. The lumbricals of the hand, extensor indicis muscle,[2] dorsal interossei of the hand, and palmar interossei insert on these bands.
  • A single median band passes down the middle of the finger along the back of the proximal phalanx, ending at the base of the middle phalanx.
  • A band known as the retinacular ligament runs obliquely along the middle phalanx, and connects the fibrous digital sheath on the anterior side of the phalanges to the extensor expansion.


  1. ^ "eMedicine - Hand, Tendon Lacerations: Extensors : Article by D Glynn Bolitho, MD, PhD, FACS". Retrieved 2008-01-20. [not in citation given]
  2. ^ Kyung Won, PhD. Chung (2005). Gross Anatomy (Board Review). Hagerstown, MD: Lippincott Williams & Wilkins. p. 43. ISBN 0-7817-5309-0. 

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