First metacarpal bone: Difference between revisions

Revision as of 12:25, 8 November 2013

Latest revision as of 16:34, 19 October 2024

(31 intermediate revisions by 25 users not shown)

Line 1:

{{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). [[PalmerAnatomical terms of ___location#Arms|Palmar]] view.

|Image2 = Gray229.png

|Caption2 = The first metacarpal (Left)

Line 11 ⟶ 10:

|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 ofproximal 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 ==

The first metacarpal bone is short and thick with a shaft thicker and broader than those of the other metacarpal bones. Its narrow shaft connects its widened base and rounded head; the former consisting of a thick [[bone#Cortical bone|cortical bone]] surrounding the open [[medullary canal]]; the latter two consisting of [[Bone#Cancellous bone|cancellous bone]] surrounded by a thin cortical shell.

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

Line 29 ⟶ 25:

=== Body/Shaft ===

The body or shaft is thick and broad&nbsp;—&nbsp;averaging {{convert|6|to|11|mm}}. On its dorsal side, the shaft is flat and wide, while the anteroposterior side is less pronounced; usually resulting in aan oval-triangular cross-section.

The dorsal surface of the shaft is weakly convex longitudinally, while its palmar, radial, and ulnar surfaces tend to be concave. The palmar (and medial) surface exhibitexhibits a blunt ridge which separates a larger lateral part&nbsp;—–&nbsp;the origininsertion of the [[opponens pollicis muscle]]&nbsp;—–&nbsp;and a smaller medial part&nbsp;—–&nbsp;the origin of the lateral head of the first [[Dorsal interossei of the hand|dorsal interosseous muscle]].

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

Line 38 ⟶ 34:

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 -->

== 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"/> TheseWhen centresthe uniteboth beforesexes fifteenthwere yearconsidered intogether, girlsthe andossification seventeenthof yearbase inof boysfirst metacarpal was seen to start between 13 and 41 months.{{cn|date=November 2019}}

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

<ref name="Doyle-Ossification">{{harvnb|Doyle|Botte|2003| loc=Ossification Centres and Accessory Bones}}</ref><!-- ref for para -->

Line 53 ⟶ 52:

== 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 ==

Line 62 ⟶ 61:

File:First metacarpal bone (left hand) - animation01.gif|First metacarpal bone of the left hand (shown in red). Animation.

File:First metacarpal bone (left hand) - animation02.gif|First metacarpal bone of the left hand. Close up.

File:Gray219 - First metacarpal bone.png|PalmerPalmar view of the left hand (first metacarpal shown in yellow).

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>

== Notes ==

{{reflistReflist|colwidth=30em}}

== References ==

{{refbegin}}

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

| last1 = Doyle | first1 = James R.

| last2 = Botte | first2 = Michael J.

Line 78:

| publisher = Lippincott Williams & Wilkins

| isbn = 0-397-51725-4

| url = httphttps://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}}

{{CommonscatCommons category|First metacarpal bone}}

{{Bones of upper extremity}}

{{DEFAULTSORT:First Metacarpal Bone}}

[[Category:Skeletal system]]

[[Category:Bones of the hand]]

[[Category:Metacarpus]]