Trapezium (bone)

Trapezium
Left hand anterior view (palmar view). Trapezium shown in red.
The left trapezium bone
Details
Articulations	1st metacarpal distally scaphoid proximally trapezoid medially 2nd metacarpal medially
Identifiers
Latin	Os trapezium, os multangulum majus
MeSH	A02.835.232.087.319.150.800
TA	A02.4.08.008
FMA	23721
Anatomical terms of bone []

The trapezium bone (greater multangular bone) is a carpal bone in the hand. It forms the radial border of the carpal tunnel.

The trapezium is distinguished by a deep groove on its anterior surface. It is situated at the radial side of the carpus, between the scaphoid and the first metacarpal bone (the metacarpal bone of the thumb). It is homologous with the first distal carpal of reptiles and amphibians.

The trapezium is an irregularly-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 and scaphoid bones.

The 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 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 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 and Flexor pollicis brevis; it also affords attachment to the transverse carpal ligament.