TRIQUETRUM FRACTURE. The triquetrum bone is one of the small bones that make up the carpus.

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1 TRIQUETRUM FRACTURE Introduction The triquetrum bone is one of the small bones that make up the carpus. It is also known as the triquetral bone, (and in the past the pyramidal or triangular bone) Triquetrum fractures in isolation are uncommon. They are usually seen in association with other ligamentous and/ or bony injury such as perilunate fracture-dislocations. They usually heal well. Anatomy The triquetrum, (Gray s Anatomy 1918) The vascular supply of the triquetrum contains rich vascular anastomotic interconnections, making non-unions very rare. Mechanism Fracture is usually due a fall on the outstretched hand. Isolated trapezium dislocations may occur but are rare. These may occur in dorsal or palmar directions. They may occur with crush injuries either or with radial-axial dislocations. Complications Significant complications are rare in cases of isolated triquetrum fractures. Possible complications with more extensive injury may include: Ulnar carpal instability, (the most significant concern).

2 Secondary degenerative osteoarthritic changes. Osteomyelitis in cases of compound injury Avascular necrosis is generally not seen in fractures of the triquetrum, due to its relatively rich blood supply. Unrecognized palmar triquetrum dislocations can manifest as carpal tunnel syndrome, at which point excision is usually recommended. Classification There are 3 principle types of triquetrum fractures: Dorsal cortical fractures. These are the most common type. Dorsal chip type fractures are only clearly seen on the lateral projection since the pisiform usually overlies the triquetrum on A-P or oblique projections of the wrist Body fractures, (usually transversely). Volar avulsion fractures. Triquetral fractures may also be associated with transcaphoid perilunate dislocations of the wrist. Clinical features The main features will be: Tenderness to ulnar aspect of dorsal wrist There may also be mild bruising or swelling. As for any bony injury the distal neurovascular status of the limb should always be carefully assessed.

3 Investigations Normal A-P radiograph of the left carpus. The triquetrum is seen in the proximal row of the carpus at the left posterior to the pisiform. On a lateral view the triquetrum will be the most dorsal bone 1

4 Plain radiography Views should include: A-P Lateral The most dorsal bone will be the triquetrum and so this will usually be the best view to detect dorsal cortical fractures (which are the most common type). Ulna deviation A small avulsion fracture from the dorsum of the triquetrum. It is seen only on the lateral projection (red arrow). The pisiform overlies the triquetrum in the AP and oblique views and so tends to obscure this type of fracture (white arrows). CT scan CT scan of the wrist is useful, in cases where the plain radiographs are inconclusive, yet clinical suspicion of significant wrist injury remains high. CT in particular is useful for suspected trapezium, trapezoid, pisiform, and hamate fractures. CT may also be useful for further defining the extent of injury.

5 MRI MRI is also useful for imaging the carpal bones in cases where plain radiography in inconclusive yet clinical suspicion remains high. Management 1. Give analgesia as clinically indicated. 2. Immobilization: Triquetrum (as well as pisiform and hamate) fractures heal well with Colles type cast immobilization and rarely require surgical intervention. Immobilization is for 4-6 weeks. 3. Surgery: Surgical intervention may be required for complex cases, where there are other associated bony and/ or ligamentous injuries References 1. Pitfalls in Orthopedic Radiography Interpretation. Michelle Lin, MD FAAEM Assistant Clinical Professor of Medicine, UC San Francisco San Francisco General Hospital Emergency Services Dr J. Hayes 26 March 2009