Trapezoid bone

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Trapezoid bone
Trapezoid bone (left hand) 01 palmar view.png
Left hand anterior view (palmar view). Trapezoid bone shown in red.
Gray226.png
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 A02.835.232.087.319.150.805
Dorlands
/Elsevier
o_07/12598807
TA A02.4.08.010
FMA 23724
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. 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.

Structure[edit]

The trapezoid is a four-sided carpal bone found within the hand. The trapezoid is found within the distal row of carpal bones.[1] :708

Surfaces[edit]

The superior surface, quadrilateral, smooth, and slightly concave, articulates with the scaphoid.

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.

The dorsal and palmar surfaces are rough for the attachment of ligaments, the former being the larger of the two.

The lateral surface, convex and smooth, articulates with the trapezium.

The medial surface is concave and smooth in front, for articulation with the capitate; rough behind, for the attachment of an interosseous ligament.

Function[edit]

The carpal bones function as a unit to provide a bony superstructure for the hand.[1] :708

Clinical Significance[edit]

Isolated fractures of the trapezoid are rare, representing a 0.4% of the total, thus being the least common of all carpal fractures. This is because it’s 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. Thus subluxations, such as ones caused by delivering blow are not uncommon. Direct trauma to the bone can also cause fracture.

Due to is rarity; a standard treatment has not been established. Having a wide range of possible treatments, including rest, surgery and casting.[2]

History[edit]

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[edit]

See also[edit]

This article uses anatomical terminology; for an overview, see Anatomical terminology.

References[edit]

This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)

  1. ^ a b 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. 
  2. ^ 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.