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.
The head is at distal end and rounded.
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.
The base is proximal end and enlarged.
- 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.
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:
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.