Trapezium (bone)

Overview
The trapezium bone (greater multangular bone) is a carpal bone, in what is commonly referred to as the wrist.

The trapezium is distinguished by a deep groove on its palmar surface. It is situated at the radial side of the carpus, between the scaphoid and the first metacarpal bone.

The etymology derives from the Greek trapezion which means "irregular quadrilateral;" literally, "a little table," from trapeza meaning table. Also, from tra- "four" and peza "foot" or "edge."

Surfaces
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.

The dorsal surface is rough.

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.

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; the lower, small and oval, with the base of the second metacarpal.

Tubercle of trapezium
The tubercle of trapezium is a anatomic tubercle, where sometimes abductor pollicis brevis muscle attaches.

Additional images
Trapecio (hueso) Os trapèze Trapezio (osso) Os trapezium 大菱形骨 Trapézio (osso) Lichobežníkovitá väčšia kosť