| Trapezoid bone | |
|---|---|
_01_palmar_view.png) Left hand anterior view (palmar view). Trapezoid bone shown in red. | |
 The left trapezoid bone. | |
| Details | |
| Articulations | Articulates with four bones: scaphoid proximally second metacarpal distally trapezium bone laterally capitate medially |
| Identifiers | |
| Latin | os trapezoideum, os multangulum minus |
| MeSH | D051223 |
| TA98 | A02.4.08.010 |
| TA2 | 1257 |
| FMA | 23724 |
| Anatomical terms of bone | |
Thetrapezoid bone (lesser multangular bone) is acarpal bone intetrapods, includinghumans. 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 itswedge-shaped form, the broad end of the wedge constituting thedorsal, the narrow end the palmar surface; and by its having four articular facets touching each other, and separated by sharp edges. It ishomologous with the "second distal carpal" of reptiles and amphibians.
The trapezoid is a four-sidedcarpal bone found within thehand. The trapezoid is found within the distal row of carpal bones.[1]: 708
Thesuperior surface, quadrilateral, smooth, and slightly concave, articulates with thescaphoid.
Theinferior surface articulates with theproximal end of thesecond metacarpal bone; it is convex from side to side, concave from before backward and subdivided by an elevated ridge into two unequal facets.
Thedorsal andpalmar surfaces are rough for the attachment of ligaments, the former being the larger of the two.
Thelateral surface, convex and smooth, articulates with thetrapezium.
Themedial surface is concave and smooth in front, for articulation with thecapitate; rough behind, for the attachment of an interosseousligament.
The carpal bones function as a unit to provide a bony superstructure for thehand.[1]: 708
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.[2]
The etymology derives from the Greektrapezion which means "irregular quadrilateral," fromtra- "four" andpeza "foot" or "edge." Literally, "a little table" fromtrapeza meaning "table" and-oeides "shaped."
_-_animation01.gif)
_-_animation02.gif)
This article incorporates text in thepublic domain frompage 225 of the 20th edition ofGray's Anatomy(1918)
