Left hand anterior view (palmar view). Trapezoid bone shown in red.
The left trapezoid bone.
articulates with four bones:|
second metacarpal distally
trapezium bone laterally
|Latin||os trapezoideum, os multangulum minus|
|Anatomical terms of bone|
The trapezoid bone (lesser multangular bone) is a carpal bone in tetrapods, 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-shaped form, the broad end of the wedge constituting the dorsal, the narrow end the palmar surface; and by its having four articular facets touching each other, and separated by sharp edges. It is homologous with the "second distal carpal" of reptiles and amphibians.
The inferior surface articulates with the 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.
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.
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."
|Wikimedia Commons has media related to Trapezoid bone.|
- Drake, Richard L.; Vogl, Wayne; Tibbitts, Adam W.M. Mitchell; illustrations by Richard; Richardson, Paul (2005). Gray's anatomy for students. Philadelphia: Elsevier/Churchill Livingstone. ISBN 978-0-8089-2306-0.
- Sadowski, RM; Montilla, RD (2008). "Rare isolated trapezoid fracture: a case report". Hand (N Y). 3: 372–4. doi:10.1007/s11552-008-9100-8. PMC 2584218. PMID 18780025.