View source for Extensor digitorum brevis manus muscle

{{Short description|Muscle on the back of the hand}}
{{Infobox anatomy
| Name        = Extensor digitorum brevis manus
| Image       = 
| Caption     = 
| Width       = 
| Image2      = 
| Caption2    = 
| Latin       = Musculus extensor digitorum brevis manus
| Greek       =
| Precursor   = 
| System      = [[Muscular system]]
| Artery      = [[Anterior interosseous artery]]
| Vein        = 
| Nerve       = [[Posterior interosseous nerve]] 
| Lymph       = 
}}

'''Extensor digitorum brevis manus''' is an extra or [[accessory muscle]] on the backside (dorsum) of the [[hand]]. It was first described by Albinus in 1758.<ref>{{cite journal |last1=Albinus |first1=Bernhardus-Siegefridus |title=De extensore digitorum brevis manus |trans-title=On the extensor of the fingers of the short hand |language=la |journal=Academicarum Annotationum |volume=4 |date=1758 |pages=28–29 |url=https://books.google.com/books?id=hCVVAAAAcAAJ&pg=PA28 }}</ref> The muscles lies in the fourth extensor compartment of the [[wrist]], and is relatively rare.<ref name="Ranade Rai Prabhu et al 2008">{{cite journal |last1=Ranade |first1=Anu V. |last2=Rai |first2=Rajalakshmi |last3=Prabhu |first3=Latha V. |last4=Rajanigandha |first4=V. |last5=Janardhanan |first5=Jiji P. |last6=Ramanathan |first6=Lakshmi |last7=Prameela |first7=M. D. |title=Incidence of Extensor Digitorum Brevis Manus Muscle |journal=HAND |date=December 2008 |volume=3 |issue=4 |pages=320–323 |doi=10.1007/s11552-008-9111-5 |pmid=18780016 |pmc=2584220 }}</ref>  It has a prevalence of 4% in the general population according to a meta-analysis.<ref name=Yammine2015>{{cite journal |last1=Yammine |first1=Kaissar |title=The prevalence of extensor digitorum brevis manus and its variants in humans: a systematic review and meta-analysis |journal=Surgical and Radiologic Anatomy |date=January 2015 |volume=37 |issue=1 |pages=3–9 |doi=10.1007/s00276-014-1312-8 |pmid=24849464 |s2cid=8863347 }}</ref> This muscle is commonly misdiagnosed as a ganglion cyst, synovial nodule or [[cyst]].<ref name="Çavdar Doğan Bayramiçli et al 1998">{{cite journal |last1=Çavdar |first1=Safiye |last2=Doğan |first2=Teoman |last3=Bayramiçli |first3=Mehmet |last4=Şehirli |first4=Ümit |last5=Yüksel |first5=Mehtap |title=An unusual variation of extensor digitorum brevis manus: A case report and literature review |journal=The Journal of Hand Surgery |date=January 1998 |volume=23 |issue=1 |pages=173–177 |doi=10.1016/S0363-5023(98)80108-1 |pmid=9523974 }}</ref><ref name="Ogura Inoue Tanabe 1987">{{cite journal |last1=Ogura |first1=Takashi |last2=Inoue |first2=Hajime |last3=Tanabe |first3=Gozo |title=Anatomic and clinical studies of the extensor digitorum brevis manus |journal=The Journal of Hand Surgery |date=January 1987 |volume=12 |issue=1 |pages=100–107 |doi=10.1016/s0363-5023(87)80171-5 |pmid=3805622 }}</ref><ref name="Paraskevas Papaziogas Spanidou Papadopoulos 2002">{{cite journal |last1=Paraskevas |first1=G. |last2=Papaziogas |first2=B. |last3=Spanidou |first3=S. |last4=Papadopoulos |first4=A. |title=Unusual variation of the extensor digitorum brevis manus: A case report |journal=European Journal of Orthopaedic Surgery & Traumatology |date=January 2002 |volume=12 |issue=3 |pages=158–160 |doi=10.1007/s00590-002-0035-4 |pmid=24573895 |s2cid=207024098 }}</ref>

== Structure ==
The extensor digitorum brevis manus usually originates from the dorsal aspect (backside) of the wrist, either from the joint capsule, the distal end (the most distant end) of the radius, the metacarpal, or from the [[Dorsal radiocarpal ligament|radiocarpal ligament]] in the area of the fourth extensor compartment.<ref name=Yammine2015/> Many variations of the muscle have been described in the literature. It could have up to four tendons with a single tendon inserting to the index or the middle finger being the two most common variations.<ref>{{cite book |last1=Le Double |first1=Anatole-Félix |title=Traité des variations du système musculaire de l'homme et de leur signification au point de vue de l'anthropologie zoologique |trans-title=Treatise on the variations of the muscular system of man and their significance from the point of view of zoological anthropology |date=1897 |publisher=Schleicher frères |url=https://archive.org/details/traitdesvariat02ledo |language=fr }}{{pn|date=April 2023}}</ref> At the insertion the tendon of the extensor digitorum brevis manus often joins the [[extensor indicis proprius]],<ref name=Yammine2015/> although it also occurs when the extensor indicis proprius is absent. It was also reported to coexist with the [[Extensor medii proprius muscle|extensor medii proprius]], another anatomical variation in the extensor compartment of the hand.<ref name="Suwannakhan Tawonsawatruk Meemon 2016">{{cite journal |last1=Suwannakhan |first1=Athikhun |last2=Tawonsawatruk |first2=Tulyapruek |last3=Meemon |first3=Krai |title=Extensor tendons and variations of the medial four digits of hand: a cadaveric study |journal=Surgical and Radiologic Anatomy |date=November 2016 |volume=38 |issue=9 |pages=1083–1093 |doi=10.1007/s00276-016-1673-2 |pmid=27056052 |s2cid=8544399 }}</ref> The muscle is supplied the [[posterior interosseous nerve]] and posterior branch of the [[anterior interosseous artery]].

=== Variation ===
The extensor digitorum brevis manus was found to be present in 4% of the population, and there was no correlation between gender, side or ancestry.<ref name="Ranade Rai Prabhu et al 2008"/> it inserted to the index finger and the middle finger in 77% and 23% of the cases, respectively.<ref name="Ranade Rai Prabhu et al 2008"/> It occurred bilaterally in 26% the total cases.

=== Development ===
At some point during the [[embryonic development]], the precursor extensor mass differentiates into three layers: radial, superficial, and deep.<ref>{{cite journal |id={{ProQuest|1301827777}} |last1=Straus |first1=William |title=The Phylogeny of the Human Forearm Extensors |journal=Human Biology |volume=13 |issue=1 |date=February 1941 |pages=23 }}</ref> The extensor digitorum brevis manus may have been originated from the deep layer, a typical location where most of the variations take place.<ref name="Ranade Rai Prabhu et al 2008"/> Some authors believe that this muscle may represent a failure of proximal migration of ulnocarpal elements of the extensor muscle mass in humans.<ref name="Suwannakhan Tawonsawatruk Meemon 2016"/><ref>{{cite journal |last1=Souter |first1=W A |title=The extensor digitorum brevis manus |journal=British Journal of Surgery |date=8 December 2005 |volume=53 |issue=9 |pages=821–823 |doi=10.1002/bjs.1800530923 |pmid=5911774 |s2cid=42145116 }}</ref>

== Functions ==
It extends the index or the middle finger. It is believed to be a substitute for the extension of the index finger when the extensor indicis proprius is absent.

== Clinical significance ==
Only a few clinical cases have been reported among more than 300 clinical and cadaveric dissections.<ref>{{cite journal |last1=Dixit |first1=Daksha |last2=Kubavant |first2=Dharati M. |last3=Lakhani |first3=Chintan J. |last4=Patel |first4=Mital M. |last5=Rathod |first5=Suresh P. |last6=Singel |first6=T.C. |title=A morphometric evaluation of Extensor digitorum brevis manus by dissection: A rare atavistic muscle of the dorsum of hand |journal=Medica Innovatica |volume=1 |issue=2 |date=2012 |pages=59–63 |url=https://www.medicainnovatica.org/December%20issue/12.pdf }}</ref> This implies that the presence of this muscle is usually asymptomatic, although the extensor digitorum brevis manus might cause a painful [[swelling (medical)|swelling]] which can potentially be misdiagnosed as other [[pathology]] such as synovial cyst and [[lipoma]].<ref name="Çavdar Doğan Bayramiçli et al 1998"/><ref name="Ogura Inoue Tanabe 1987"/><ref name="Paraskevas Papaziogas Spanidou Papadopoulos 2002"/>

== See also ==
* [[Extensor indicis muscle|Extensor indicis proprius muscle]]
* [[Extensor medii proprius muscle]]
* [[Extensor indicis et medii communis muscle]]
* [[List of anatomical variations]]

==References==
{{reflist}}

==Further reading==
* {{cite journal |last1=AlMarshad |first1=Felwa A |last2=Mahabbat |first2=Nehal |last3=Alkhalifah |first3=Ahmed |last4=Alhumaidan |first4=Mohammed I |last5=Jarman |first5=Abdulaziz |title=A Rare Case of Painful Hand Swelling |journal=Cureus |date=28 September 2022 |volume=14 |issue=9 |pages=e29691 |doi=10.7759/cureus.29691 |doi-access=free |pmid=36320946 |pmc=9615604 }}
* {{cite journal |last1=Bharambe |first1=Vaishaly |last2=Shevade |first2=Sapna |last3=Patel |first3=Dinesh |last4=Manvikar |first4=Purushottam Rao |last5=Bajpayee |first5=Pallavi Gupta |title=A study of the extensor tendons of the hand from point of view of evolution |journal=Journal of the Anatomical Society of India |date=December 2017 |volume=66 |issue=2 |pages=112–117 |doi=10.1016/j.jasi.2017.12.001 }}
* {{cite journal |last1=Rao Poleneni |first1=Sushma |title=Variant muscle on dorsal aspect of hand with review of literature |journal=Medpulse International Journal of Anatomy |date=2021 |volume=19 |issue=2 |pages=30–32 |doi=10.26611/10011924 |s2cid=238886068 |doi-access=free }}

{{Muscles_of_upper_limb}}

[[Category:Hand]]
[[Category:Accessory muscle]]
[[Category:Muscles of the upper limb]]
[[Category:Anatomical variations]]