Latin os lunatum TA A02.4.08.005 | Dorlands
/Elsevier o_07/12598459 FMA 23712 | |
 | ||
Articulations radius proximally
capitate and hamate distally
scaphoid laterally
triangular medially MeSH A02.835.232.087.144.663 | ||
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.
Contents
Structure
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, medially with the triquetral, and distally with the capitate. 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 and a lateral ligament to the triquetrum. 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. The medial surface possesses a smooth and quadrilateral facet for articulation with the triquetral. 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 Lunate bone commences between 18 months and 4 years and 3 months.
Function
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.
Clinical relevance
The lunate bone is the most frequently dislocated carpal bone.
Etymology
The name of the lunate bone derives from the "crescent-shaped" (Latin: lunatus), from Latin luna ("moon"), from the bone's resemblance to a crescent moon. In amphibians and reptiles, the bone is instead referred to as the intermedium, because of its position between the other two proximal carpals.