Five long bones of the palm, numbered from the thumb, lying between the wrist bones and the finger bones
Metacarpal bones — the bones of the palm.
Anatomy · Bones
Metacarpal bones
Five bones of the palm
Hand · palm
The metacarpal bones are the five long bones of the palm, lying between the carpal bones of the wrist and the phalanges of the fingers and thumb. They are numbered one to five from the thumb, and their heads form the knuckles. The first, at the base of the thumb, is separate from the others, giving the thumb its freedom of movement.
How to spot them
- ▸Five slender long bones fanning out from the wrist through the palm, each with a base, shaft (body) and rounded head
- ▸Numbered 1 to 5 from the thumb; the heads form the knuckles of a clenched fist
- ▸The first is shorter, stouter and set apart from the rest, articulating with the trapezium in a saddle joint
- ▸Second and third are fixed; fourth and fifth have some anteroposterior movement, aiding the power grip
What to know
Their rounded heads form the knuckles when the fist is clenched
Metacarpal bones — the metacarpophalangeal joints.
A fracture of the neck of the little-finger one, classically from punching a hard surface, is nicknamed after a sport
Metacarpal bones — the boxer's fracture (of the fifth).
A fracture-dislocation at the base of the thumb's one carries the name of a Dublin surgeon, Bennett; a comminuted version bears an Italian name, Rolando
Metacarpal bones — Bennett's fracture (1882) and Rolando fracture (1910) of the first.
The one at the base of the thumb sits apart from the rest and meets a saddle-shaped wrist bone, giving the thumb's freedom to oppose
Metacarpal bones — the first, at the carpometacarpal joint with the trapezium.
The two on the index and middle fingers are firmly anchored, while those of the ring and little fingers can move forwards, deepening the hollow of the palm in a power grip
Metacarpal bones — the fourth and fifth are more mobile.
The Greek meta means 'beyond' — beyond the wrist
Metacarpal bones — meta + karpos.
Key ideas
- Because the first is separate and rotated, the thumb can oppose the other fingers; the other four form a fixed arch.
- The metacarpals are numbered from the thumb (1) to the little finger (5).
Quick-fire facts
- •There are five metacarpals in each hand, giving 10 in all; together with 8 carpals and 14 phalanges they make 27 bones in each hand.
- •Each has a base (proximal end, articulating with the distal carpal row), a shaft, and a head (distal end, articulating with the proximal phalanx).
- •The heads form the knuckles; the metacarpophalangeal joints are the 'big knuckles'.
- •The first metacarpal forms the carpometacarpal joint of the thumb with the trapezium, a saddle joint allowing opposition.
- •The fifth metacarpal fracture, usually of the neck, is called the 'boxer's fracture'.
- •Bennett's fracture is an oblique intra-articular fracture-dislocation of the base of the first metacarpal; Rolando's is a comminuted (Y- or T-shaped) fracture of the same place.
- •A short fourth metacarpal is a recognised sign in Turner syndrome (Archibald's sign).
- •The word is from Greek meta, beyond, and karpos, the wrist.
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Sources
- OpenStax — Anatomy and Physiology 2e — 8.2 Bones of the Upper Limb
- TeachMeAnatomy — Bones of the Upper Limb