Triquetrum
Os Triquetrum
location_on Proximal row of carpal bones, on the ulnar (pinky) side
The triquetrum is a pyramidal bone on the medial side of the proximal carpal row. It articulates with the pisiform on its palmar surface and with the lunate laterally. The triquetrum does not directly articulate with the ulna; instead, it is separated by the triangular fibrocartilage complex (TFCC). It is the second most commonly fractured carpal bone after the scaphoid.
Key Anatomical Features
- Pyramidal shape with three articular surfaces
- Palmar oval facet articulates with the pisiform bone
- Does not directly contact the ulna; separated by the TFCC
- Hamate facet on the distal lateral surface for the hamate
- Dorsal surface is non-articular and is the site of chip fractures
Muscle Attachments
| Muscle | Attachment | Action |
|---|---|---|
| No direct muscular attachments | Stabilized by carpal ligaments | N/A |
| Ulnar collateral ligament | Ulnar styloid to triquetrum | Stabilizes the ulnar side of the wrist |
| Lunotriquetral ligament | Between lunate and triquetrum | Links the proximal carpal row |
| Triquetrohamate ligament | Between triquetrum and hamate | Stabilizes the medial carpal column |
Joints and Articulations
| Joint | Type | Connects to |
|---|---|---|
| Pisotriquetral joint | Synovial plane | Pisiform |
| Lunotriquetral joint | Synovial plane | Lunate |
| Triquetrohamate joint | Synovial plane | Hamate |
Common Pathologies
Triquetrum fracture
The second most common carpal fracture. Dorsal chip fractures from ligament avulsion are most frequent, while body fractures are less common and may indicate perilunate injury.
Lunotriquetral ligament tear
Injury to the interosseous ligament between lunate and triquetrum causing ulnar-sided wrist pain and carpal instability.
Pisotriquetral arthritis
Degenerative changes at the pisotriquetral joint causing ulnar-sided wrist pain exacerbated by gripping. Pisiform excision is curative.
Clinical Relevance
Triquetral dorsal chip fractures are best seen on the lateral wrist radiograph as a small bony fragment dorsal to the proximal carpal row. They result from hyperextension injuries with dorsal impingement or avulsion by the dorsal radiocarpal ligament. The TFCC separates the triquetrum from the ulna and is a common source of ulnar-sided wrist pain when torn.
Development and Ossification
The triquetrum ossifies from a single center appearing around age 2-3, making it one of the earliest carpal bones to ossify. It is entirely cartilaginous at birth.
Did You Know?
- Triquetrum means three-cornered in Latin, describing its pyramidal shape
- The triquetrum is the second most commonly fractured carpal bone
- Unlike most carpal bones, the triquetrum does not directly contact any forearm bone
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