Editing Trapezoid bone

{{Short description|Carpal (wrist) bone}}
{{Infobox bone
| Name          = Trapezoid bone
| Latin         = os trapezoideum, os multangulum minus
| Image         = Trapezoid bone (left hand) 01 palmar view.png
| Caption       = Left hand anterior view (palmar view). Trapezoid bone shown in red.
| Image2        = Gray226.png
| Caption2      = The left trapezoid bone.
| Origins       =
| Insertions    =
| Articulations = Articulates with four bones:<br>[[scaphoid]] proximally<br>[[second metacarpal]] distally<br>[[trapezium bone]] laterally<br>[[capitate]] medially
}}
The '''trapezoid bone''' ('''lesser multangular bone''') is a [[Carpal bones|carpal bone]] in [[tetrapod]]s, including [[humans]]. It is the smallest bone in the distal row of carpal bones that give structure to the palm of the hand. It may be known by its [[wedge (mechanical device)|wedge]]-shaped form, the broad end of the wedge constituting the [[dorsal surface|dorsal]], the narrow end the palmar surface; and by its having four articular facets touching each other, and separated by sharp edges. It is [[homology (biology)|homologous]] with the "second distal carpal" of reptiles and amphibians.

==Structure==
The trapezoid is a four-sided [[carpal bone]] found within the [[hand]]. The trapezoid is found within the distal row of carpal bones.<ref name=GRAYS2005>{{cite book|last=Drake|first=Richard L.|title=Gray's anatomy for students|year=2005|publisher=Elsevier/Churchill Livingstone|location=Philadelphia|isbn=978-0-8089-2306-0|author2=Vogl, Wayne |author3=Tibbitts, Adam W.M. Mitchell  |author4=illustrations by Richard |author5= Richardson, Paul }}</ref> {{rp|708}}

===Surfaces===
The ''[[Anatomical terms of location|superior surface]]'', quadrilateral, smooth, and slightly concave, articulates with the [[scaphoid]].

The ''[[Anatomical terms of location|inferior surface]]'' articulates with the [[Anatomical terms of location|proximal]] end of the [[second metacarpal bone]]; it is convex from side to side, concave from before backward and subdivided by an elevated ridge into two unequal facets.

The ''[[Anatomical terms of location|dorsal]]'' and ''[[Anatomical terms of location|palmar]] surfaces'' are rough for the attachment of ligaments, the former being the larger of the two.

The ''[[Anatomical terms of location|lateral surface]]'', convex and smooth, articulates with the [[Trapezium (bone)|trapezium]].

The ''[[Anatomical terms of location|medial surface]]'' is concave and smooth in front, for articulation with the [[capitate]]; rough behind, for the attachment of an interosseous [[ligament]].

==Function==
The carpal bones function as a unit to provide a bony superstructure for the [[hand]].<ref name=GRAYS2005 /> {{rp|708}}

==Clinical Significance==

Isolated fractures of the trapezoid are rare, representing 0.4% of the total, thus being the least common of all carpal fractures. This is due to the bone being in a fairly protected position. Distally, it forms a stable, relatively immobile joint with the second metacarpal, radially and proximally it forms strong ligaments with the trapezium and the capitate ulnarly, scaphoid respectively.

However, injury can occur through axial force applied to the second metacarpal base. Subluxations, such as ones caused by delivering a blow, are not uncommon. Direct trauma to the bone can also cause fracture.

Due to its rarity, standard treatment has not been established. A wide range of treatments are possible, including rest, surgery and casting.<ref>{{cite journal | pmc = 2584218 | pmid=18780025 | doi=10.1007/s11552-008-9100-8 | volume=3 | title=Rare isolated trapezoid fracture: a case report | year=2008 | journal=Hand (N Y) | pages=372–4 | last1 = Sadowski | first1 = RM | last2 = Montilla | first2 = RD| issue=4 }}</ref>

==History==
The etymology derives from the Greek ''trapezion'' which means "irregular quadrilateral," from ''tra-'' "four" and ''peza'' "foot" or "edge." Literally, "a little table" from ''trapeza'' meaning "table" and ''-oeides'' "shaped."

==Additional images==
<gallery>
 File:Trapezoid bone (left hand) - animation01.gif|Position of trapezoid bone (shown in red). Left hand. Animation.
 File:Trapezoid bone (left hand) - animation02.gif|Trapezoid bone of the left hand. Close up. Animation.
 File:Trapezoid bone.jpg|Trapezoid bone.
 File:RightHumanPosteriorDistalRadiusUlnaCarpals - Trapezoid bone.png|Right hand posterior view (dorsal view). Thumb on bottom.
 File:Gray220 - Trapezoid bone.png|Trapezoid shown in yellow. Left hand. Dorsal surface.
 File:Gray219 - Trapezoid bone.png|Trapezoid shown in yellow. Left hand. Palmar surface.
 File:Gray422 - Trapezoid bone.png|Transverse section across the wrist (palm on top, thumb on left). Trapezoid bone shown in yellow (labelled as "''Lesser Multang''").
 File:Ospoignet - Trapezoid bone.png|Cross section of wrist (thumb on left). Trapezoid shown in red (labelled as "''Lesser Multang''").
</gallery>

== See also ==
{{Commons}}
{{Anatomy-terms}}
*[[Carpal bone]]

== References ==
{{Gray's}}
{{Reflist}}

{{Bones of upper extremity}}
{{Portal bar|Anatomy}}
{{Authority control}}

{{DEFAULTSORT:Trapezoid Bone}}
[[Category:Skeletal system]]
[[Category:Wrist]]
[[Category:Bones of the hand]]
[[Category:Carpal bones]]