[Dynamic study of the distal radioulnar joint with computerized tomography]

The authors describe a CT technique which allows the dynamic study of the inferior radioulnar joint. The examination consists of 4 CT slices, three of them acquired at the same level-i.e., the radioulnar joint- in the prone, intermediate and supine positions, respectively. The last slice is acquired, with the patient in the prone position, at the base of the styloid process where the triangular fibrocartilage is demonstrated. The distal radioulnar ligaments are not directly visible. Nineteen patients complaining of painfully impaired pronation and supination because of previous trauma (11 Colles fractures, 7 distortions and 1 Galeazzi lesion) were examined with this technique. In all patients, both wrists were studied to obtain normal parameters. The radioulnar joint was evaluated superimposing a draft on the dynamic images, which demonstrated that, in healthy limbs, during movement the ulnar epiphysis is always contained between two parallel lines drawn on the volar and dorsal surfaces of the radial epiphysis, respectively. It was also confirmed that supination is possible up to 110-135 degrees from the support plane. CT demonstrated different causes of impaired movements in the affected joints: in 12 cases some fibrous density tissue was seen at the ulnar epiphysis on the volar aspect and considered to be the evolution of a traumatic hematoma; 6 patients presented dorsal subluxation of the ulna during movement; finally, volar subluxation was detected only in one case. In 6 patients the triangular fibrocartilage was detached; in 1 patient an intraarticular fluid collection was demonstrated. In 3 patients CT detected no abnormalities. The fibrous tissue is responsible for impaired movements and causes the detached triangular fibrocartilage to shrink. The authors believe that this simple CT technique can yield useful pieces of information for accurate surgical planning.