Capitate bone

This article is about a bone in the wrist. For use in botany, see Stigma (botany).

Capitate bone
File:Capitate bone (left hand) 01 palmar view.png Left hand anterior view (palmar view). Capitate-bone shown in red.
File:Gray227 retouched.png The left capitate bone. Left: ulnar surface (little-finger-side surface). Right: radial surface (thumb-side surface)
Details
Latin	Os capitatum; os magnum
Identifiers
MeSH	A02.835.232.087.319.150.150
Dorlands /Elsevier	o_07/12598140
TA
TH	{{#property:P1694}}
TE	{{#property:P1693}}
FMA	23727
Anatomical terms of bone [[[d:|edit on Wikidata]]]

The capitate bone /ˈkæpᵻteɪt/ is the largest of the carpal bones in the human hand, and occupies the center of the wrist. It presents, above, a rounded portion or head, which is received into the concavity formed by the scaphoid and lunate bones; a constricted portion or neck; and below this, the body. The bone is also found in many other mammals, and is homologous with the "third distal carpal" of reptiles and amphibians.

Structure

The capitate is the largest carpal bone found within the hand. The capitate is found within the distal row of carpal bones. The capitate lies directly adjacent to the metacarpal of the ring finger on its distal surface, has the hamate on its ulnar surface and trapezoid on its radial surface, and abuts the lunate and scaphoid proximally.

Surfaces

The superior surface is round, smooth, and articulates with the lunate bone.

The inferior surface is divided by two ridges into three facets, for articulation with the second, third, and fourth metacarpal bones, that for the third being the largest.

The dorsal surface is broad and rough.

The palmar surface is narrow, rounded, and rough, for the attachment of ligaments and a part of the adductor pollicis muscle.

The lateral surface articulates with the lesser multangular by a small facet at its anterior inferior angle, behind which is a rough depression for the attachment of an interosseous ligament. Above this is a deep, rough groove, forming part of the neck, and serving for the attachment of ligaments; it is bounded superiorly by a smooth, convex surface, for articulation with the scaphoid bone.

The medial surface articulates with the hamate bone by a smooth, concave, oblong facet, which occupies its posterior and superior parts; it is rough in front, for the attachment of an interosseous ligament.

Variation

The capitate bone variably articulates with the metacarpal of the index finger.

Ossification

The ossification of capitate starts at 1 – 5 months.

Function

The carpal bones function as a unit to provide a bony superstructure for the hand.

Clinical Significance

A Capitate fracture accounts for 1.3% of all wrist fractures. Isolated fractures of the capitate comprise only 0.3% and are often non-displace. It is positioned in This is since the capitate is at the centre of the Carpal region and is therefore quite well protected Capitate fractures occur together with fractures of another Carpal bone - the Scaphoid.

Various mechanisms for fractures of the capitate have been postulated. Adler et al. described three mechanisms—the first is direct trauma to the dorsal surface of the bone, the second is fall on the palm with the wrist in forced extension and the third is fall on the forcefully flexed hand; the second being the most frequent and the third rarest.

In the case of an acute Capitate fracture where there is x-ray evidence of excellent alignment of the fracture fragments, the attending doctor will immobilise the wrist in a plaster or lightweight Wrist Brace. Once the cast has been removed the patient begins physiotherapy to regain the range of movement of the wrist joint and strength in the muscles involved.

If x-rays show that the Capitate fracture fragments are out of alignment surgery is indicated. A surgeon can use small compression screws) or K-Wires to unite the two pieces of bone.The headless compression screw has advantage over the K-wire as it provides compression across the fracture site and allows early motion. It may be the case that the ligament between the Capitate and the Scaphoid bone is also injured, is so this would be repaired at the same time.

Because the Capitate has a poor blood supply there are sometimes complications with the healing process. This may manifest itself as a diffuse ache in the wrist upon activity, and can persist for many months. This is due to a breakdown of the Capitate caused by the lack of blood supply and healing (Avascular Necrosis). Nonunion has been reported as the most common complication; 19.6% to 56% in isolated capitate fractures. Early diagnosis is key to prevent this.

History

The etymology derives from the Latin Latin: capitātus, "having a head," from Latin: capit-, meaning "head."

Additional images

• Capitate bone (left hand) - animation01.gif

  Position of capitate bone (shown in red). Left hand. Animation.

• Capitate bone (left hand) - animation02.gif

  Capitate bone of the left hand. Close up. Animation.

• Capitatum ant.jpg

  Capitate bone of the left hand. Ulnar surface (little-finger-side surface)

• Capitatum post.jpg

  Capitate bone of the left hand. Radial surface (thumb-side surface)

• RightHumanPosteriorDistalRadiusUlnaCarpals - Capitate bone.png

  Right hand posterior view (dorsal view). Thumb on bottom.

• RightHumanAnteriorDistalRadiusUlnaCarpals - Capitate bone.png

  Right hand anterior view (palmar view). Thumb on top.

• Gray219 - Capitate bone.png

  Capitate bone shown in yellow. Left hand. Palmar surface.

• Gray220 - Capitate bone.png

  Capitate bone shown in yellow. Left hand. Dorsal surface.

• Gray422 - Capitate bone.png

  Transverse section across the wrist (palm on top, thumb on left). Capitate bone shown in yellow.

• Ospoignet - Capitate bone.png

  Cross section of wrist (thumb on left). Capitate shown in red.

See also

This article uses anatomical terminology; for an overview, see Anatomical terminology.

• Carpal bone

References

This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)