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Metacarpal bones

Synonyms: metacarpal, middle hand bones
German: Os metacarpale

1 Definition

The 5 metacarpal bones (ossa metacarpalia) form the bony basis of the middle hand (metacarpus).

2 Classification

The metacarpals when adhering to correct labelling are numbered consecutively as a system from lateral to medial, whereby the slightly splayed metacarpal of the thumb carried the number I:

  • os metacarpale I
  • os metacarpale II
  • os metacarpale III
  • os metacarpale IV
  • os metacarpale V
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3 Anatomy

3.1 Common features

All metacarpal bones consist of three sections. Seen from proximal to distal these are:

  • base (also: extremitas carpalis or proximalis)
  • shaft (corpus)
  • head (capitulum or caput, also: extremitas phalangealis or distalis)

The base of the metacarpal has a cubic basic form. Their concave cartilaginous surfaces articulate with the carpal bones and in their totality form the carpometacarpal joint.

The shaft has a triangular cross-section. In the basic anatomical position (palms facing forward), the apex of the triangle faces forward, the base points to the rear of the hand. This side is in the distal portion of the metacarpals an almost flat bone surface, over which the tendons of the extensors run. The other two sides, ie, the medial and lateral side of the metacarpals, are concave. This is where the musculi interossei are seated. Frontally these are pushed together to form a bone ridge.

The head has a convex surface cartilage whose extension in the anteroposterior direction is greater than in the transverse. On either side of the head there are small tubercles, onto which the collateral ligaments of the metacarpophalangeal joints are respectively fixed.

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