Ulnar styloid fractures occur in association with ~60% of distal radius fractures. 

Pathology

Usually, this kind of fracture occurs as the result of a fall on an outstretched arm and is often associated with a distal radius fracture ¹.

Most common are small avulsion fractures involving the tip of the ulnar styloid with transverse fractures through the base less common ².

In the paediatric and adolescent forearm, it should be remembered that in very rare situations the ulnar styloid can arise from a separate ossification centre, but mostly separation of the ulnar styloid is caused by injury ¹.

Radiographic features

Plain radiograph

The fracture is easy to recognise on plain film. Sometimes the fractures may not seem very apparent on x-ray if there is no displacement.

In children, up to 15% of ulnar styloid process fractures may be occult as the ulnar styloid process does not start to ossify until 5-9 years ².

Treatment and prognosis

In patients with distal radius fractures, a concomitant ulnar styloid fracture does not affect outcomes ³, and a lack of union of these fractures does not significantly affect late functional results ^1,2. Fractures at the very base of the ulnar styloid can cause instability of the distal radioulnar joint (DRUJ) and disruption of the triangular fibrocartilage complex (TFCC) insertion at the ulnar fovea. It is argued that these injuries, therefore, need open stabilisation ¹.

Differential diagnosis

• persistent ulnar styloid or other accessory ossicles of the wrist that occur around the distal ulna

• pathological fracture e.g. erosive arthropathy such as gout