Editing Trapezium (bone)

{{short description|Bone of the wrist}}
{{Other uses|Trapezium (disambiguation)}}
{{Infobox bone
| Name          = Trapezium
| Latin         = os trapezium, os multangulum majus
| Image         = Trapezium bone (left)01 palmar view.png
| Caption       = Left hand anterior view (palmar view). Trapezium shown in red.
| Image2        = Gray225.png
| Caption2      = The left trapezium bone ("navicular" refers to scaphoid, "lesser multangular" refers to trapezoid)
| Origins       =
| Insertions    =
| Articulations = [[first metacarpal|1st metacarpal]] distally <br>[[scaphoid]] proximally <br>[[Trapezoid bone|trapezoid]] medially <br>[[second metacarpal|2nd metacarpal]] medially
}}
The '''trapezium''' bone ('''greater multangular bone''') is a [[Carpal bones|carpal]] bone in the [[hand]]. It forms the [[radius (bone)|radial]] border of the [[carpal tunnel]].

==Structure==
The trapezium is distinguished by a deep groove on its anterior surface. It is situated at the radial side of the [[Carpal bones|carpus]], between the [[scaphoid]] and the first [[metacarpal]] bone (the metacarpal bone of the thumb). It is [[homology (biology)|homologous]] with the '''first distal carpal''' of reptiles and amphibians.

===Surfaces===
The trapezium is an irregular-shaped [[carpal bone]] found within the [[hand]]. The trapezium is found within the distal row of carpal bones, and is directly adjacent to the [[metacarpal]] bone of the [[thumb]]. On its ulnar surface are found the [[Trapezoid bone|trapezoid]] and [[scaphoid]] 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}}

The ''[[Anatomical terms of location|superior surface]]'' is directed upward and medialward; medially it is smooth, and articulates with the [[scaphoid]]; laterally it is rough and continuous with the lateral surface.

The ''[[Anatomical terms of location|inferior surface]]'' is oval, concave from side to side, convex from before backward, so as to form a saddle-shaped surface for articulation with the base of the [[first metacarpal bone]]. This saddle-shaped articulation is partially responsible for the [[Carpometacarpal joint#Thumb|thumb]]'s opposable motion.

The ''dorsal surface'' is smooth.

The ''palmar surface'' is narrow and rough. At its upper part is a deep groove, running from above obliquely downward and medialward; it transmits the tendon of the [[Flexor carpi radialis]], and is bounded laterally by an oblique ridge. This surface gives origin to the [[Opponens pollicis]] and to the [[Abductor pollicis brevis muscle|Abductor]] and [[Flexor pollicis brevis]]; it also affords attachment to the [[transverse carpal ligament]].

The ''lateral surface'' is broad and rough, for the attachment of ligaments.

The ''medial surface'' presents two facets; the upper, large and concave, articulates with the [[trapezoid bone]]; the lower, small and oval, with the base of the [[second metacarpal]].

===Tubercle of trapezium===
The tubercle of trapezium is a [[tubercle]] found on the anterior surface of the bone.<ref name=GRAYS2005 />{{rp|708}} It is where sometimes [[abductor pollicis brevis muscle]] attaches.

==Function==
The carpal bones function as a unit to provide a bony superstructure for the [[hand]]. The trapezium is the most radial of the bones surrounding the [[carpal tunnel]].<ref name=GRAYS2005 />{{rp|708}} It is important in thumb movement.<ref name=EATHORNE2005>{{cite journal|last=Eathorne|first=SW|title=The wrist: clinical anatomy and physical examination--an update.|journal=Primary Care|date=Mar 2005|volume=32|issue=1|pages=17–33|pmid=15831311|doi=10.1016/j.pop.2004.11.009}}</ref>

==Clinical relevance==
The trapezium is susceptible to arthritis at the joint with the [[metacarpal]] bone of the thumb, due to overuse.<ref name=EATHORNE2005 />

==History==
The etymology derives from the Greek ''trapezion'' which means "a little table", from ''trapeza'' meaning "table", itself from ''(te)tra-'' "four" and ''pod-'' "foot". The name was first documented in 1840.<ref>{{cite web|last=Harper|first=Douglas|title=Trapezium|url=http://www.etymonline.com/index.php?term=trapezium|work=Online Etymology Dictionary|access-date=5 January 2014}}</ref>

==Additional images==
<gallery>
 File:Trapezium bone (left) - animation01.gif|Position of trapezium (shown in red). Left hand. Animation.
 File:Trapezium bone (left) - animation02.gif|Trapezium of the left hand.
 File:Trapezium bone.jpg|Trapezium bone.
 File:RightHumanPosteriorDistalRadiusUlnaCarpals - Trapezium bone.png|Right hand posterior view (dorsal view). Thumb on bottom.
 File:RightHumanAnteriorDistalRadiusUlnaCarpals - Trapezium bone.png|Right hand anterior view (palmar view). Thumb on top.
 File:Gray219 - Trapezium bone.png|Bones of the left hand. Palmar surface. Trapezium shown in yellow.
 File:Gray220 - Trapezium bone.png|Bones of the left hand. Dorsal surface. Trapezium shown in yellow.
 File:Ospoignet - Trapezium.png|Cross section of wrist (thumb on left). Trapezium shown in red (labelled as "''Greater Multang''").
 File:Gray422 - Trapezium.png|Transverse section across the wrist and digits. Trapezium is shown in yellow (labelled as "''Greater Multang''").
 File:Gray334.png|Ligaments of wrist. Anterior view
 File:Gray416.png|Tendons of forefinger and vincula tendina.
</gallery>

==See also==
{{Commons category|Trapezium (bone)}}
{{Anatomy-terms}}
* [[Carpal bone]]
*[[Finger]]
*[[Hand]]

==References==
{{Reflist}}

{{Bones of upper extremity}}
{{Authority control}}

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