Os Triquetrum – Anatomy, Function & Injuries
The os triquetrum is a small carpal bone located on the ulnar side of the wrist. It belongs to the proximal carpal row and plays a key role in wrist stability and movement.
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The os triquetrum is a small carpal bone located on the ulnar side of the wrist. It belongs to the proximal carpal row and plays a key role in wrist stability and movement.
What is the Os triquetrum?
The os triquetrum (also known as the triquetral bone or os triquetrale) is one of the eight carpal bones that make up the wrist. It is situated in the proximal carpal row on the ulnar side, meaning the side of the little finger. Its name derives from the Latin word triquetrus, meaning triangular, referring to its distinctive three-sided shape. The bone articulates with the lunate, the pisiform, and the hamate, and is indirectly connected to the ulna via the triangular fibrocartilage complex (TFCC).
Anatomy and Location
The os triquetrum is positioned between the lunate bone on the radial side and the pisiform bone on the palmar side. It forms a critical part of the proximal carpal row and is tightly connected to neighboring bones by strong ligaments. Its ulnar position makes it an important stabilizer of the ulnocarpal joint.
Joint Connections
- Lunate bone: medial articular surface
- Pisiform bone: palmar articular surface
- Hamate bone: distal articular surface
- Ulna: indirect connection via the TFCC
Function
The os triquetrum fulfills several important functions within the wrist joint:
- Participation in flexion and extension of the wrist
- Participation in ulnar deviation (bending toward the little finger side)
- Stabilization of the ulnocarpal joint
- Transmission of forces from the hand to the forearm bones
Common Injuries and Conditions
Triquetrum Fracture
A triquetrum fracture is the second most common carpal fracture after the scaphoid fracture. It typically results from a fall onto an outstretched hand or from direct trauma. Two main types are recognized:
- Dorsal avulsion fracture: The most common type, in which a small bony fragment is pulled off the dorsal surface of the bone.
- Body fracture: Less common, involves the entire bone body and is often associated with other carpal injuries.
Symptoms of a Triquetrum Fracture
- Pain on the ulnar (little finger) side of the wrist
- Swelling and tenderness over the triquetrum
- Restricted wrist range of motion
- Increased pain during ulnar deviation
Other Conditions
- Ligamentous instability: Injuries to the lunotriquetral ligaments can lead to wrist instability.
- Osteoarthritis: Degenerative changes of the triquetrum as part of carpal osteoarthritis.
- Os triquetrum bipartitum: A rare anatomical variant in which the triquetral bone consists of two separate bony segments.
Diagnosis
Several imaging techniques are used to evaluate injuries of the os triquetrum:
- X-ray: Standard first-line imaging; dorsal avulsion fractures are typically visible on a lateral view.
- Computed tomography (CT): Provides detailed visualization of fracture patterns and joint involvement.
- Magnetic resonance imaging (MRI): Particularly useful for assessing ligament injuries and occult (hidden) fractures.
Treatment
Conservative Treatment
Most triquetrum fractures, especially dorsal avulsion fractures, respond well to conservative management:
- Immobilization of the wrist in a plaster or synthetic cast for 4 to 6 weeks
- Pain management with anti-inflammatory medications
- Physiotherapy to restore strength and range of motion after healing
Surgical Treatment
In cases of complex fractures, instability, or non-union, surgical intervention may be required:
- Osteosynthesis (fixation of bone fragments using screws or wires)
- Ligament reconstruction for cases of ligamentous instability
References
- Standring, S. (Ed.) - Gray's Anatomy: The Anatomical Basis of Clinical Practice. 41st Edition. Elsevier, 2015.
- Mayfield, J.K. et al. - Carpal dislocations: pathomechanics and progressive perilunar instability. Journal of Hand Surgery, 1980; 5(3):226-241.
- Amadio, P.C. & Taleisnik, J. - Fractures of the carpal bones. In: Green's Operative Hand Surgery. 6th Edition. Churchill Livingstone, 2011.
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Related search terms: Os triquetrum + Triquetrum + Os triquetrale + Triquetral bone