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Extensor expansion

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Extensor expansion
Extensor expansion covers the tendon of extensor digitorum tendons over the proximal phalanges
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Anatomical terminology

An extensor expansion (extensor hood,[1] 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.[2]

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.

Bands

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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,[3] 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, inserting into 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.

Function

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The extensor expansion allows for contractile forces from the extensor compartment muscles to be transferred to the phalanges. It also balances the forces across the phalanges.[1]

References

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  1. ^ a b Blankenbaker, Donna G.; Davis, Kirkland W.; Sonin, Andrew; Crim, Julia R., eds. (2016-01-01), "Extensor Tendon Injury, Wrist and Fingers", Diagnostic Imaging: Musculoskeletal Trauma (Second Edition), Diagnostic Imaging, Elsevier, pp. 468–473, doi:10.1016/b978-0-323-39253-2.50118-x, ISBN 978-0-323-39253-2, retrieved 2021-01-04
  2. ^ "eMedicine - Hand, Tendon Lacerations: Extensors : Article by D Glynn Bolitho, MD, PhD, FACS". Retrieved 2008-01-20.[failed verification]
  3. ^ 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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