Triquetral bone

Bone: Triquetral bone
Shown is the right hand, palm down (left) and palm up (right). Proximal: A=Scaphoid, B=Lunate, C=Triquetral, D=Pisiform Distal: E=Trapezium, F=Trapezoid, G=Capitate, H=Hamate
The left triquetal bone
Latin	os triquetrum, os pyramidale, os triangulare
Gray's	subject #54 224
Articulations	articulates with three bones: lunate laterally pisiform in front hamate distally triangular articular disk which separates it from the lower end of the ulna.
MeSH	Triquetrum+Bone

The triquetral bone (also called triquetrum, pyramidal, three-cornered or triangular bone, and formerly cuneiform bone) is located in the wrist on the medial side of the proximal row of the carpus between the lunate and pisiform bones. It is on the ulnar side of the hand, but does not articulate with the ulna. It connects with the pisiform, hamate, and lunate bones. It is the 3rd most commonly fractured carpal bone.

The triangular bone may be distinguished by its pyramidal shape, and by an oval isolated facet for articulation with the pisiform bone. It is situated at the upper and ulnar side of the carpus. To facilitate its palpation in an exam, the hand must be radially deviated so that the triquetrium moves out from under the ulnar styloid process. The triquetrum may be difficult to find, since it also lies under the pisiform.

The etymology derives from the Latin triquetrus which means "three-cornered." In reptiles and amphibians, the bone is instead referred to as the ulnare, since (at least in the most primitive fossils) it articulates with the ulna.

Surfaces

The superior surface presents a medial, rough, non-articular portion, and a lateral convex articular portion which articulates with the triangular articular disk of the wrist.

The inferior surface, directed lateralward, is concave, sinuously curved, and smooth for articulation with the hamate. The dorsal surface is rough for the attachment of ligaments.

The volar surface presents, on its medial part, an oval facet, for articulation with the pisiform; its lateral part is rough for ligamentous attachment.

The lateral surface, the base of the pyramid, is marked by a flat, quadrilateral facet, for articulation with the lunate.

The medial surface, the summit of the pyramid, is pointed and roughened, for the attachment of the ulnar collateral ligament of the wrist.

See also

• Bone terminology
• Terms for anatomical location

Additional images

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  Triquetral bone.

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  Bones of the left hand. Volar surface.

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  Bones of the left hand. Dorsal surface.

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  Triquetral fracture as seen on X ray.