The trapezium (also known as the greater multangular) is one of the eight carpal bones of the hand. It is the most lateral (radial) bone of the distal row, located between the scaphoid and the first metacarpal bone. It articulates with the scaphoid proximally, the trapezoid medially, and the thumb and index metacarpals distally. The trapezium and trapezoid are collectively known as the multangulars.
On this page:
Gross anatomy
Osteology
The trapezium has six surfaces in total:
rough palmar surface which contains a medial groove and prominent tubercle
elongated rough dorsal surface
large lateral surface
concave medial surface
large dorsolateral sellar surface (i.e. saddle-shaped) 3 which projects distally between the thumb and index metacarpals, and also has a small distomedial facet articulating with the index metacarpal base
small concave proximal surface
Articulations
articulates with the scaphoid at the midcarpal joint
articulates with the trapezoid at its intercarpal joint
articulates with the thumb metacarpal at the carpometacarpal joint of the thumb
Attachments
Musculotendinous
superficial head of flexor pollicis brevis arises from the tubercle distally
the opponens pollicis arises from the tubercle between flexor pollicis brevis and abductor pollicis brevis
the abductor pollicis brevis arises from the tubercle proximally
Ligamentous
two layers of the flexor retinaculum attach either side of the groove of the trapezium
radial collateral ligament attaches to the lateral surface
capsule of the carpometacarpal joint of the thumb attaches to the lateral surface
Relations
The tendon of flexor carpi radialis runs through the groove and the radial artery is directly related to the dorsal surface.
Arterial supply
Supplied by distal branches of the radial artery, primarily via the dorsal surface 2.
Venous drainage
Drained by tributaries of the radial vein.
Variant anatomy
Females have a significantly smaller sellar surface, with a fundamentally different shape of that surface 1.
Radiographic features
Plain radiograph
The trapezium may be visualized on a number of series of the distal upper limb including:
CT/MRI
CT or MRI imaging will demonstrate the trapezium and should be considered if there is clinical suspicion of occult injury.
Development
Ossification
The trapezium begins to ossify in the 4th to 5th year.
History and etymology
Trapezium derives from the ancient Greek word "trapezion", which means "small table". It later came to mean a four-sided figure with no parallel sides.