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Other Terms: Cuneiform bone of hand, Triangular bone, Triquetral bone, Triquetrum, Os triquetrum
This bone is the medial most bone of the proximal carpal row. It is pyramidal in shape with the base of the pyramid facing the lunate bone laterally and the apex of the pyramid projecting medially as the attachment of the ulnar collateral ligament of the wrist. Its ventral surface is identified by a projecting oval facet for the pisiform bone. Dorsally the bone is rough for the attachment of ligaments. The distal, proximal, and lateral surfaces form smooth articular surfaces for neighboring bones.
Triquetris is Latin meaning three corners. The bone was so named because of its triangular shape. Synonyms used for this bone throughout history are triangular, cuneiform, cuboid, pyramidale.
The triquetral bone articulates with three bones: the lunate, pisiform, and hamate bones. The broad lateral base of the triquetral bone forms a square articular surface with the lunate bone. The distal end of the bone faces laterally forming the sinuous, concavely curved facet for articulation with the hamate bone. The prominent ventromedial facet for the pisiform bone is oval shaped. Its proximal end forms a smooth facet for articulation with the articular disc of the distal radioulnar joint.
The triquetral ossifies from a single center that arises, on average, during the third year.