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TriquetrumEdit

The Triquetrum, also known as the triquetral bone, is one of the eight carpal bones that make up the human wrist. The name derives from Latin, meaning “three-cornered,” a nod to its small, triangular shape. As a component of the carpus, the triquetrum plays a key role in the intricate gliding motions and stability of the wrist, forming joints with several neighboring bones and participating in the complex ligaments that brace the wrist.

In the standard anatomical arrangement, the triquetrum sits on the ulnar (medial) side of the proximal row of carpal bones, between the lunate and the pisiform. Its position places it at the convergence of the proximal carpal row and the distal row, contributing to both radiocarpal and midcarpal articulations. The bone’s compact, wedge-like body and its dorsal and palmar surfaces suit the three primary facets that engage with adjacent structures.

Anatomy and location

  • Shape and position: The triquetrum is a small, triangular bone on the ulnar side of the wrist. It lies in the proximal carpal row and is adjacent to the lunate, with the pisiform resting on its anterior aspect.
  • Articular relationships: It articulates proximally with the lunate, anteriorly with the pisiform (via a fibrous or non-synovial contact that is reinforced by surrounding ligaments), and distally with the bones of the distal carpal row, notably the hamate and capitate as part of the midcarpal joint network.
  • Shape and surfaces: Its surfaces accommodate multiple small articular facets that accommodate the contact with neighboring carpal bones and ligaments, contributing to the wrist’s complex, multi-axial movements.
  • Adjacent structures: The triquetrum is bounded on its medial side by the ulnar styloid region and is linked to the triangular fibrocartilage complex via the ulnar side of the wrist, helping stabilize the distal radioulnar interface.

Ligaments, attachments, and movements

  • Ligamentous connections: The triquetrum is stabilized by intercarpal ligaments and by connections to the pisiform through the pisiform-triquetral ligaments. The broader radiocarpal and intercarpal ligament systems bind the triquetrum to its neighbors, allowing controlled motion while preserving joint congruity.
  • Tendinous associations: The triquetrum receives its mechanical context within the wrist from surrounding tendinous structures and the flexor and extensor retinacula, which guide tendon gliding across the carpal bones during forearm and hand movement.
  • Functional role: By participating in the proximal–distal carpal articulations, the triquetrum helps distribute loads across the wrist during weight-bearing and gripping, contributing to stability when the wrist is in extension or ulnar deviation.

Clinical significance

  • Fractures and injuries: Fracture of the triquetrum is a recognized wrist injury, typically resulting from hyperextension or axial loading of the wrist. It may occur in isolation or with other carpal injuries. Because displacement can be minimal, such fractures can be initially overlooked on plain radiographs.
  • Diagnosis and imaging: If a triquetral fracture is suspected but not evident on X-ray, advanced imaging such as computed tomography (CT) or magnetic resonance imaging (MRI) can clarify fracture pattern and any associated ligamentous or TFCC (triangular fibrocartilage complex) injury.
  • Treatment considerations: Management ranges from immobilization in a cast or brace to surgical intervention in cases of displaced fractures or concomitant instability. Fractures involving the adjacent TFCC or midcarpal joints may require a broader treatment plan addressing both bone and soft tissue injuries.
  • Related conditions: The triquetrum’s relationships with the TFCC and the pisiform mean that injuries to this region can often accompany ulnar-sided wrist pain, TFCC tears, or pisiform dislocation in certain trauma scenarios.

Development and variation

  • Ossification and growth: The triquetrum ossifies from a single primary center and becomes a distinct bone during childhood and adolescence, with completion of its development over the late childhood to early adulthood period. Variations in size and shape exist among individuals, reflecting normal anatomical diversity.
  • Anatomical variation: While the general placement and connections are consistent, minor variations in articular surface architecture and ligamentous attachments occur and can influence wrist kinematics on a person-by-person basis.

Etymology and naming

  • The term triquetrum derives from Latin, reflecting its three-cornered, triangular form. It is also commonly referred to as the triquetral bone in some anatomical texts, with the same anatomical entity described by different traditions of nomenclature.

See also