Lunate
The lunate (os lunatum or semilunar) is one of the carpal bones and is a component of the proximal carpal row.
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Gross anatomy
Osteology
The lunate is crescent-shaped with a proximal convex articular facet and a distal concave articular facet. On the medial surface is a square-shaped facet and on the lateral surface is a semilunar facet. It is broader anteriorly than it is posteriorly.
Articulations
- along with the scaphoid and triquetrum forms the distal articular surface of the radiocarpal joint
- intercarpal articulations
- scaphoid (lateral)
- capitate (distal)
- triquetrum (medial)
- hamate (distal and medial) - only in type II lunate
- articulates with the triangular fibrocartilage complex
Attachments
Musculotendinous
- nil
Ligamentous
- intrinsic ligaments
- extrinsic ligaments
- palmar: radiolunotriquetral, radioscapholunate, ulnolunate ligaments
Blood supply
- arterial supply: branches from the dorsal radiocarpal arch and dorsal intercarpal arch supply the lunate via the dorsal and palmar surfaces (80%) or palmar surface only (20%) 2
Variant anatomy
- variation in articular facets (see: lunate morphology)
- lunotriquetral coalition
- associated accessory ossicles
- os epilunate
- os hypotriquetrum
- os hypolunatum
- bipartite lunatum 6
Radiographic appearance
Plain radiograph
- frontal projection (neutral wrist position)
- more than one-half should contact distal radial articular surface 3
- should have a 'square shape' and the intercarpal joints should be uniformly 1-2 mm wide
- forms part of the carpal arcs
Development
Ossification
Ossifcation typically begins at age four and is complete by age six or seven 2.
History and etymology
From the Latin "luna" meaning moon, referring to the crescent-moon shape of the lunate. It was first named the "lunatum" in 1653 by Lyser, and has also been termed the "lunare" or "semilunare".
Related pathology
Related Radiopaedia articles
Anatomy: Upper limb
-
skeleton of the upper limb
- clavicle
- scapula
- humerus
- radius
- ulna
- carpal bones (mnemonic)
- metacarpals
- phalanges
- accessory ossicles of the upper limb
- accessory ossicles of the shoulder
- accessory ossicles of the elbow
-
accessory ossicles of the wrist (mnemonic)
- os centrale carpi
- os epilunate
- os styloideum
- os hamuli proprium
- lunula
- os triangulare
- trapezium secondarium
- os paratrapezium
- os radiostyloideum (persistent radial styloid)
- joints of the upper limb
-
shoulder joint
- articulations
- associated structures
- joint capsule
-
bursae
- subacromial-subdeltoid (SASD) bursa
- subscapular recess
- subcoracoid bursa
- coracoclavicular bursa
- supra-acromial bursa
- ligaments
-
movements
- scapulothoracic joint
- glenohumeral joint
- arm flexion
- arm extension
- arm abduction
- arm adduction
- arm internal rotation (medial rotation)
- arm external rotation (lateral rotation)
- circumduction
- blood supply - scapular anastomosis
- ossification centers
-
elbow joint
- proximal radioulnar joint
- ligaments
- associated structures
- movements
- alignment
- blood supply - elbow anastomosis
- development
-
wrist joint
- articulations
-
ligaments
- intrinsic ligaments
- extrinsic ligaments
- associated structures
- extensor retinaculum
- flexor retinaculum
- joint capsule
- movements
- alignment
- ossification
-
hand joints
- articulations
- carpometacarpal joint
-
metacarpophalangeal joint
- palmar ligament (plate)
- collateral ligament
-
interphalangeal joint
- palmar ligament (plate)
- collateral ligament
- movements
- articulations
-
shoulder joint
- spaces of the upper limb
- muscles of the upper limb
- shoulder girdle
- anterior compartment of the arm
- posterior compartment of the arm
- anterior compartment of the forearm
- posterior compartment of the forearm (extensors)
- hand (mnemonic)
- accessory muscles
- blood supply to the upper limb
-
arteries
- subclavian artery (mnemonic)
- axillary artery
- brachial artery (proximal portion)
- ulnar artery
- radial artery
- veins
-
arteries
- innervation of the upper limb
- intercostobrachial nerve
-
brachial plexus (mnemonic)
- branches from the roots
- branches from the trunks
- branches from the cords
- lateral cord
- posterior cord
- medial cord
- terminal branches
- lymphatic drainage of the upper limb