Trapezium

The trapezium (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.

Gross anatomy

Osteology

The trapezium has a number of surfaces (six in total):

1. rough palmar surface which contains a medial groove and prominent tubercle
2. elongated rough dorsal surface
3. large lateral surface
4. concave medial surface
5. large dorso-lateral sellar surface which projects distally between the thumb and index metacarpals, and also has a small disto-medial facet articulating with the index metacarpal base.
6. 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.

Blood supply

Supplied by distal branches of the radial artery, primarily via the dorsal surface ².

Radiographic features

Plain radiograph

content pending

Cross-section

content pending

Development

Ossification

The trapezium begins to ossify in the fourth to fifth year.

Variant anatomy

Females have a significantly smaller sellar surface, with a fundamentally different shape of that surface ¹.

Related pathology

• base of thumb arthritis
• trapezium fracture

History and etymology

Greek: originally 'small table', later a four-sided figure with no parallel sides.