First metacarpal bone: Difference between revisions

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{{Short description|Bone of the hand}}

{{Infobox Bone

|Name = First metacarpal bone

|Latin = os metacarpale I

|GraySubject = 55

|GrayPage = 228

|Image = First metacarpal bone (left hand) 01 palmar view with label.png

|Caption = First metacarpal of the left hand (shown in red). [[Anatomical terms of ___location#Arms|Palmar]] view.

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|Insertions =

|Articulations =

|MeshName = Metacarpal+Bones

|MeshNumber = A02.835.232.087.319.550

|FMA = 23899

}}

The '''first metacarpal bone''' or the '''[[metacarpal bone]] of the [[thumb]]''' is the first bone proximal to the thumb. It is connected to the [[trapezium (bone)|trapezium]] of the [[Carpal bones|carpus]] at the first [[carpometacarpal joint]] and to the proximal thumb [[Phalanges of the hand|phalanx]] at the first [[metacarpophalangeal joint]].

== Characteristics ==

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The base is significantly different from the bases of the other metacarpals. It is trumpet-shaped and ends in a saddle-shaped articular surface matching that of the trapezial articular surface. The configuration of the thumb carpometacarpal joint plays an important role in the mechanism of opposition. The articular surface is delimited by a thick, crest-like ridge extending around its circumference.

On the palmar and lateral side of the base is the insertion of the tendon of the [[abductor pollicis longus muscle]], usually featuring a small tubercle. The origin of the first [[PalmarDorsal interossei musclesof the hand|palmardorsal interosseous muscle]] is on the ulnar aspect of the base, and can sometimes extend onto the shaft. In contrast to the other metacarpals, the first metacarpal has no articular facets on the sides of its base (for intermetacarpal articulations) because it articulates exclusively with the trapezium.

<ref name="Doyle-Base">{{harvnb|Doyle|Botte|2003| loc=Base of the Thumb Metacarpal}}</ref><!-- ref for subsection -->

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== Ossification ==

[[File:Gray234 - First metacarpal bone.png|thumb|Ossification of hand bones. First metacarpal shown in yellow.]]

The metacarpal bone of the thumb has two centres of ossification: a primary centre in the shaft and a secondary centre in the base. This contrasts to the other four metacarpal bones where the secondary centre is found in the head. The ossification process begins in the shaft during the ninth week of prenatal life, and in the base during the second year of life in girls and the third year in boys.<ref name="Doyle-Ossification"/> When the both sexes were considered together, the ossification of base of first metacarpal was seen to start between 13 and 41 months.<ref name="AB">{{cite journal|last1=Balachandran|first1=Ajay|author2=Anooj Krishna|author3=Moumitha Kartha|author4=Thomas Jerry|author5=Prem T.N.|author6=Libu G.K.|title=Ossification of Distal end of Radius & Base of First Metacarpal in Forensic Age Estimation in the Kerala Population|journal=Scholars Journal of Applied Medical Sciencescn|date=December 2013|volume=1|issue=6|pages=796–800|url=http://saspublisher.com/wp-content/uploads/2013/12/SJAMS16796-800.pdf|accessdate=4 JanuaryNovember 20142019}}</ref>

These centres unite before fifteenth year in girls and seventeenth year in boys.

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== Fractures ==

Fractures to the first metacarpal bonebones account for 30-40% of all hand fractures, andof which 25% ofoccur allin metacarpalthe fracturesfirst metacarpal (second to fractures to the fifth metacarpal bone). 80% of fractures to the first metacarpal occur at its base.

<ref>{{harvnb|UpToDate|20102018}}</ref>

Common fractures to the thumb metacarpal include [[Bennett's fracture]] and [[Rolando's fracture]].

== Additional images ==

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File:Gray220 - First metacarpal bone.png|Dorsal view of the left hand (first metacarpal shown in yellow).

File:Rolando fracture.jpg|Fracture of the first metacarpal ([[Rolando's fracture]]).

File:Slide4val.JPG|First metacarpal bone. Deep dissection.

</gallery>

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== References ==

{{refbegin}}

* {{cite book | ref = harv | year = 2003

| last1 = Doyle | first1 = James R.

| last2 = Botte | first2 = Michael J.

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| publisher = Lippincott Williams & Wilkins

| isbn = 0-397-51725-4

| url = https://books.google.com/books?id=96jG5n-vmPcC&pg=PA66&lpg=PA65

}}

* {{cite web | ref = harv{{harvid|UpToDate|2018}} | year = 20102018

| title = First (thumb) metacarpal fractures

| publisher = UpToDate

| url = http://www.uptodate.com/patients/content/topic.do?topicKey=~29ZLQtWPNSVF72

| accessdateaccess-date = May2 2010February 2018

}}

{{refend}}

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{{DEFAULTSORT:First Metacarpal Bone}}

[[Category:Skeletal system]]

[[Category:Bones of the hand]]

[[Category:Metacarpus]]