Triquetral fractures are carpal bone fractures generally occurring on the dorsal surface of the triquetrum. The triquetral may be fractured by means of impingement from the ulnar styloid, shear forces, or avulsion from strong ligamentous attachments. They are the second commonest carpal bone fracture, after the scaphoid.

Clinical presentation

Commonest history is trauma to the outstretched hand with carpal extension ⁴:

• pain is usually on the ulnar aspect of the wrist, exacerbated by extension/flexion of the wrist
• swelling over the dorsum of the hand with a tender dorsal aspect of triquetrum may be found on exam

Pathology

The usual injury mechanism is falling onto an outstretched hand in ulnar deviation. Less commonly, it may be caused by a direct blow to the dorsum of the hand, a situation where commonly other carpal fractures are seen.

Radiographic features

There are three fracture patterns often observed, dorsal avulsion fractures, triquetral body fractures and volar avulsion fractures ³. Dorsal avulsion fractures account for about 95% all triquetral fractures, most of the remainder are body fractures ⁴.

Dorsal avulsion fracture

On plain film, dorsal avulsion injuries are best detected on a lateral projection, where typically an avulsed flake of bone is identified lying posteriorly to the triquetral bone (see pooping duck sign). CT or MR may be more sensitive than conventional radiographs for detection of avulsion injuries.

Triquetral body fracture

Triquetral body fractures appear as clear fracture lines through the body, they are best seen on the oblique projection of the wrist, although cross sectional imaging may be required to further elucidate extent.

Volar avulsion fractures

Volar avulsion fractures are avulsions of the palmar ulnar triquetral/lunotriquetral ligament and are best seen on a radial deviation projection of the wrist ³. 

Treatment and prognosis

Surgical intervention is rarely required, but a persistently symptomatic chip fracture may require excision.

Differential diagnosis

Imaging differential considerations include:

• accessory os triquetrum/os triquetrum secundarium/os triangulare