Radiographic Deteremination of Distal Radioulnar Joint Dislocation

Distal radioulnar joint (DRUJ) dislocation can be caused by fractures of the distal radius (most common cause) and distal ulna (e.g., styloid process) and injury to the triangular fibrocartilage complex, dorsal and palmar radioulnar ligaments, interosseous membrane, or joint capsule. Radiography is generally unreliable for diagnosis because of the difficulty in obtaining standard views, but recognition of typical findings and associated injuries is nonetheless important.

Frontal radiographs may reveal an avulsion fracture of the triangular fibrocartilage complex, an ulnar styloid fracture or nonunion, and shortening of the radius. Increased overlap between the radius and ulna indicates volar ulnar dislocation, while increased distance between the sigmoid notch and the distal ulna indicates dorsal ulnar dislocation (more common).

A true lateral radiograph of the wrist with the forearm in neutral rotation (i.e., without supination or pronation) is needed. With true lateral views, the pisoscaphoid distance (between anterior margins of the scaphoid and pisiform) and the radioulnar distance (between the posterior margins of the radius and ulna) can be measured in both wrists. The difference between the two pisoscaphoid distances should be less than 3 mm and the difference between the two radioulnar distances should be less than 5 mm. A radioulnar difference of 6 mm or more is diagnostic of dislocation and a radioulnar difference between 5 mm and 6 mm is considered borderline, requiring additional imaging.

References

• Tsai PC, Paksima N. The distal radioulnar joint. Bull NYU Hosp Jt Dis. 2009;67(1):90-6.
• Nakamura R, Horii E, Imaeda T, Tsunoda K, Nakao E.Distal radioulnar joint subluxation and dislocation diagnosed by standard roentgenography. Skeletal Radiol. 1995 Feb;24(2):91-4.