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Metacarpal Bones

The Metacarpal bones are the bones present in the hands. Metacarpal bones are located in between the phalanges of the fingers and the carpal bones of the wrist and creates the intermediate part of the skeletal hand. The hand consist of five metacarpal bones which are conventionally numbered 1 to 5 from lateral (radial) to medial (ulnar) side.

Each of the five metacarpals are related to one digit:

  • Metacarpal I – Thumb.
  • Metacarpal II – Index finger.
  • Metacarpal III – Middle finger.
  • Metacarpal IV – Ring finger.
  • Metacarpal V – Little finger.

Parts of Metacarpal Bones

Every metacarpal is a small long bone and is composed of 3 parts: (a) head, (b) shaft, and (c) base.

 Metacarpal Bones: Parts of Metacarpal Bones

Metacarpal Bones: Parts of Metacarpal Bones

Head

The head is at distal end and rounded.

Shaft

The shaft goes between head and base. It’s concave on palmar aspect and on sides. The dorsal surface of shaft presents a triangular area in its distal part.

Base

The base is proximal end and enlarged.

Articulations

  • The metacarpal bone articulate proximally with distal row of carpal bones forming carpometacarpal joints.
  • Metacarpal bones articulate with each other and forms intermetacarpal joints.
  • Articulates distally with proximal phalanges to form metacarpophalangeal joints.

Ossification

Every metacarpal ossifies by 2 centers: 1 primary center for the shaft and the 1 secondary center for the head. The period of appearance of centers and their fusion is provided in the box below:

Center Time of appearance Fusion
Primary centre for shaft 9th week of IUL
Secondary centre for head of second, third, fourth, and fifth metacarpal 2 years 16 years
Secondary centre for base for first metacarpal 2 years 18 years

Clinical Significance

Bennet’s fracture: It’s an oblique fracture of the base of 1st metacarpal. It’s intra-articular and could be related to subluxation or dislocation of metacarpal.

Boxer’s fracture: It is a fracture of neck of metacarpal, and most generally includes neck of 5th metacarpal.

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By Dr. Joseph H Volker | 2018-10-25T11:20:43+00:00 October 25th, 2018|Anatomy, Bones and Cartilages, Upper Limb|0 Comments