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Description[edit | edit source]
The trapezium bone is one of eight carpal bones that forms part of the wrist joint. The word trapezium is derived from the Greek word trapezion which means “a little table”. It is an irregular-shaped carpal bone and part of the radial side of the wrist. It is also called the greater multangular bone.
Structure[edit | edit source]
The trapezium is a four-sided bone with multiple articulation surfaces and an irregular shape. It can be distinguished by a deep groove on its anterior surface through which the flexor carpi radialis muscle runs and a tubercle on the anterior side that serves as an attachment for soft tissue structures. It is situated in the distal row of carpal bones directly adjacent to the first metacarpal bone (metacarpal bone of the thumb). The tubercle of the trapezium can be palpated at the base of the thenar eminence when the wrist is extended.
Function[edit | edit source]
The trapezium, together with the other carpal bones give bony structure to the wrist and hand. The trapezium is one of the carpal bones that form the carpal tunnel and is the most radial of these bones. It plays an important role in thumb movement and serves as an attachment for muscles and ligaments.
Articulations[edit | edit source]
The trapezium articulates with four bones. On the proximal side, it articulates with the scaphoid. On the medial side, it articulates with the trapezoid and second metacarpal. Distally it articulates with the first metacarpal. This articulation is saddle-shaped and partially responsible for opposition of the thumb. The joint and articulation with the first metacarpal bone can often be overused and leads to arthritis of the trapezium bone and surrounding joints. 
Muscle attachments[edit | edit source]
The flexor carpi radialis muscle runs through the deep groove on the anterior side. This surface also serves as origin to the opponens pollicis and flexor pollicis brevis muscles as well as the transverse carpal ligament.
The abductor pollicis brevis muscle attaches to the tubercle of the trapezium.