Lunate bone
Carpal bone in the human hand
The lunate bone (semilunar bone) is a carpal bone in the human hand. It is distinguished by its deep concavity and crescentic outline. It is situated in the center of the proximal row carpal bones, which lie between the ulna and radius and the hand. The lunate carpal bone is situated between the lateral scaphoid bone and medial triquetral bone.
01Structure
The lunate is a crescent-shaped carpal bone found within the hand. The lunate is found within the proximal row of carpal bones. Proximally, it abuts the radius. Laterally, it articulates with the scaphoid bone, medially with the triquetral bone, and distally with the capitate bone. The lunate also articulates on its distal and medial surface with the hamate bone.
The lunate is stabilised by a medial ligament to the scaphoid bone and a lateral ligament to the triquetral bone. Ligaments between the radius and carpal bone also stabilise the position of the lunate, as does its position in the lunate fossa of the radius.
Bone
The proximal surface of the lunate bone is smooth and convex, articulating with the radius. The lateral surface is flat and narrow, with a crescentic facet for articulation with the scaphoid bone. The medial surface possesses a smooth and quadrilateral facet for articulation with the triquetral bone. The palmar surface is rough, as is the dorsal surface. The dorsal surface is broad and rounded. The distal surface of the bone is deep and concave.
Blood supply
The lunate receives its blood supply from dorsal and palmar branches.
Variation
The lunate has a variable shape. About one-third of lunate bones do not possess a medial facet, meaning they do not articulate with the hamate bone. Additionally, in about 20% of people, blood supply may arise from palmar vessels alone.
Ossification
The ossification of the lunate bone commences between 18 months and 4 years 3 months.
02Function
The carpal bones function as a unit to provide a bony superstructure for the hand. As a proximal carpal bone, the lunate is also involved in movement of the wrist.
03Clinical relevance
The lunate bone is the most frequently dislocated carpal bone. For its diagnosis, a little-known depression on the dorsal aspect of the wrist, known as the lunate foveola, is used.
04Etymology
Sources and credits
This article is adapted from the Wikipedia article “Lunate bone”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- TwoAspectsOfRightLunate.png by Henry Gray, Public domain
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