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Other Terms: Greater multangular bone, Trapezial bone, Trapezium bone, Os trapezium
This is an irregular shaped bone presenting six surfaces. It sits on the radial side of the carpus in the distal row of carpal bones. It is bounded proximally by the scaphoid bone and distally by the first metacarpal bone. On its rough palmar surface it can be identified by a distinct groove and a prominent tubercle. Its rough dorsal surface contributes to the floor of the anatomical snuff box where the radial artery crosses it as it courses into the hand. Its proximal, distal, and medial surfaces present smooth articular surfaces forming joint surfaces with adjacent bones. Laterally the bone is roughened for the attachment of ligaments.
Trapezium is from the Greek word trapeza meaning a four-legged table. The word was extended to mean any four-sided structure with no two sides parallel. Synonymous names used for this bone throughout history are the greater multangular and rhomboides.
The trapezium articulates with four bones: the scaphoid, trapezoid, first metacarpal, and second metacarpal. On the proximal surface is a small oval facet for articulation with the scaphoid bone. The distal surface presents a saddle-shaped oval for articulation with the first metacarpal bone. The medial surface has a larger concave facet proximally for articulation with the trapezoid bone and distally a smaller oval facet for articulation with the second metacarpal bone.
The trapezium ossifies from one center that appears, on average, between the fourth and sixth year, typically during the fourth year in females and sometime during the fifth to sixth in males. As with the other carpal bones, the timing of ossification can vary from these averages.