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{{short description|Special connective attachments by which the extensor tendons insert into the phalanges}}
{{Infobox anatomy|Name=Extensor expansion|Latin=|Caption=Extensor expansion|Image2=Grant 1962 87.png|Caption2=Extensor expansion covers the tendon of extensor digitorum tendons over the proximal phalanges|Precursor=|System=|Artery=|Vein=|Nerve=|Lymph=}}

An '''extensor expansion''' ('''extensor hood''',<ref name=":0">{{Citation|title=Extensor Tendon Injury, Wrist and Fingers|date=2016-01-01|url=http://www.sciencedirect.com/science/article/pii/B978032339253250118X|work=Diagnostic Imaging: Musculoskeletal Trauma (Second Edition)|pages=468–473|editor-last=Blankenbaker|editor-first=Donna G.|series=Diagnostic Imaging|publisher=Elsevier|language=en|doi=10.1016/b978-0-323-39253-2.50118-x|isbn=978-0-323-39253-2|access-date=2021-01-04|editor2-last=Davis|editor2-first=Kirkland W.|editor3-last=Sonin|editor3-first=Andrew|editor4-last=Crim|editor4-first=Julia R.|url-access=subscription}}</ref> '''dorsal expansion''', '''dorsal hood''', '''dorsal aponeurosis'''{{citation needed|date=October 2014}}) is the special connective attachments by which the [[Extensor tendon compartments of the wrist|extensor tendons]] insert into the [[Phalanx bone|phalanges]].

These flattened tendons ([[aponeurosis]]) of extensor muscles span the proximal and middle phalanges.<ref>{{cite web |url=http://www.emedicine.com/plastic/topic324.htm |title=eMedicine - Hand, Tendon Lacerations: Extensors : Article by D Glynn Bolitho, MD, PhD, FACS |access-date=2008-01-20 }}{{Failed verification|date=December 2012}}</ref>

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 bones|phalanx]].

==Bands==
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]],<ref name="isbn0-7817-5309-0">{{cite book |author=Kyung Won, PhD. Chung |title=Gross Anatomy (Board Review) |publisher=Lippincott Williams & Wilkins |location=Hagerstown, MD |year=2005 |isbn=0-7817-5309-0 |page=43}}</ref> [[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 ==
The extensor expansion allows for contractile forces from the [[Extensor compartment of the forearm|extensor compartment]] muscles to be transferred to the phalanges. It also balances the forces across the phalanges.<ref name=":0" />

==References==
{{reflist}}

==External links==
* {{NormanAnatomy|lesson5musofpostforearm}}
* {{KansasHandKinesiology|ligaments/fingdorsup.htm}}

{{Upper limb general}}

[[Category:Muscular system]]
[[Category:Tendons]]

{{musculoskeletal-stub}}

Extensor expansion - Revision history

imported>OAbot: Open access bot: url-access updated in citation with #oabot.