metakarpal

Metacarpal bones are the five long bones of the hand that connect the wrist to the fingers. They are numbered I through V from the thumb to the little finger. Each metacarpal has a proximal base articulating with the distal row of carpal bones at the carpometacarpal joints, a shaft, and a distal head that forms the knuckles by articulating with the proximal phalanges at the metacarpophalangeal joints. The first metacarpal differs in articulation at the carpometacarpal joint, which is a saddle joint allowing opposition.

Functionally, metacarpals provide the framework of the palm, transmit loads from the fingers to the forearm, and act as levers for finger flexion and grasp. They are surfaces for muscle and ligament attachments and contribute to the wide range of hand movement.

Nerve and blood supply come from the branches of the radial and ulnar arteries and the median and ulnar nerves; vascular supply includes dorsal and palmar metacarpal arteries.

Clinical notes: metacarpal fractures are common; fractures of the neck of the fifth metacarpal are often called boxer's fractures. Base fractures of the first metacarpal and shaft fractures can occur with trauma. Diagnosis is by radiography; treatment ranges from casting to surgical fixation, depending on fracture pattern, displacement, and clinical context.

Etymology: from Greek meta- 'beyond' and karpos 'wrist' (the term metacarpal is used in humans and many other vertebrates to describe these bones).

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