The fifth metacarpal bone (metacarpal bone of the little finger or pinky finger) is the most medial and second-shortest of the
metacarpal bones
In human anatomy, the metacarpal bones or metacarpus form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist, which forms the connection to the forearm. The metacarpal bones ...
.
Surfaces
It presents on its base one facet on its superior surface, which is concavo-convex and articulates with the
hamate
The hamate bone (from Latin hamatus, "hooked"), or unciform bone (from Latin ''uncus'', "hook"), Latin os hamatum and occasionally abbreviated as just hamatum, is a bone in the human wrist readily distinguishable by its wedge shape and a hook-l ...
, and one on its radial side, which articulates with the
fourth metacarpal
The fourth metacarpal bone (metacarpal bone of the ring finger) is shorter and smaller than the third.
The base is small and quadrilateral; its superior surface presents two facets, a large one medially for articulation with the hamate, and a sma ...
.
On its ulnar side is a prominent tubercle for the insertion of the tendon of the
extensor carpi ulnaris muscle
In human anatomy, the extensor carpi ulnaris is a skeletal muscle located on the ulnar side of the forearm. The extensor carpi ulnaris acts to extend and adduct at the carpus/wrist from anatomical position.
Being an extensor muscle, extensor car ...
.
The dorsal surface of the body is divided by an oblique ridge, which extends from near the ulnar side of the base to the radial side of the head. The lateral part of this surface serves for the attachment of the fourth
Interosseus dorsalis; the medial part is smooth, triangular, and covered by the extensor
tendon
A tendon or sinew is a tough, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability ...
s of the
little finger
The little finger, or pinkie, also known as the baby finger, fifth digit, or pinky finger, is the most ulnar and smallest digit of the human hand, and next to the ring finger.
Etymology
The word "pinkie" is derived from the Dutch word ''pink ...
.
The palmar surface is similarly divided: Its lateral side (facing the fourth metacarpal) provides origin for the third
palmar interosseus, its medial side contains the insertion of
opponens digiti quinti.
Clinical significance
A
fracture
Fracture is the separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. If a displa ...
of the
fourth and/or fifth metacarpal bones transverse neck secondary due to axial loading is known as a
boxer's fracture.
[Shultz, S. J., Houglum, P. A., Perrin, D. H. (2010). Examination of Musculoskeletal Injuries. Chicago: Human Kinetics] The fifth metacarpal bone is the most common bone to be injured when throwing a punch.
Ossification
The ossification process begins in the shaft during prenatal life, and in the head between 11th and 37th months.
Additional images
File:Fifth metacarpal bone (left hand) - animation01.gif, Fifth metacarpal bone of the left hand (shown in red). Animation.
File:Fifth metacarpal bone (left hand) - animation02.gif, Fifth metacarpal bone of the left hand. Close up.
File:Gray219 - Fifth metacarpal bone.png, Palmer view of the left hand (fifth metacarpal shown in yellow).
File:Gray220 - Fifth metacarpal bone.png, Dorsal view of the left hand (fifth metacarpal shown in yellow).
File:Boxers fracture-lateral xray.JPG, Fracture of the fifth metacarpal ( boxer's fracture).
See also
*
Metacarpus
In human anatomy, the metacarpal bones or metacarpus form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist, which forms the connection to the forearm. The metacarpal bones ...
*
First metacarpal bone
The first metacarpal bone or the metacarpal bone of the thumb is the first bone proximal to the thumb. It is connected to the trapezium of the carpus at the first carpometacarpal joint and to the proximal thumb phalanx at the first metacarpophal ...
*
Second metacarpal bone
The second metacarpal bone (metacarpal bone of the index finger) is the longest, and its base the largest, of all the metacarpal bones.''Gray's Anatomy'' (1918). See infobox.
Human anatomy
Its base is prolonged upward and medialward, forming a ...
*
Third metacarpal bone
The third metacarpal bone (metacarpal bone of the middle finger) is a little smaller than the second.
The dorsal aspect of its base presents on its radial side a pyramidal eminence, the styloid process, which extends upward behind the capitate; ...
*
Fourth metacarpal bone
The fourth metacarpal bone (metacarpal bone of the ring finger) is shorter and smaller than the third.
The base is small and quadrilateral; its superior surface presents two facets, a large one medially for articulation with the hamate, and a sm ...
References
Skeletal system
Bones of the hand
Metacarpus
{{Portal bar, Anatomy