Computerized tomography in the diagnosis of subluxation of the distal radioulnar joint

BACKGROUND: The diagnosis of distal radioulnar joint (DRUJ) subluxation is difficult. Routine radiographs are imprecise in clinical analysis. However, the anatomy and dynamic configuration of this articulation have been clearly defined utilizing computerized tomography (CT). Three CT criteria for the evaluation of DRUJ subluxation have been reported: Mino's criteria, the epicenter method and the congruity method. Previous reports discussed these criteria in the analysis of symptomatic DRUJ, but no clear conclusion has been reached. The purpose of this study is to investigate accurate criteria of CT in defining subluxation of the DRUJ. METHODS: Eighty distal radioulnar joints in 40 patients with suspected DRUJ subluxation underwent CT scans of both symptomatic and asymptomatic wrists. The CT scan was obtained through the DRUJ with the forearm in neutral rotation, active full supination and active full pronation. Three CT criteria were used to assess the DRUJ in all positions of unstable and normal wrists. RESULTS: Overall, 54 wrists were included in the final analysis. Seventeen symptomatic wrists had frank DRUJ instability diagnosed from true lateral radiographs, and 11 were reconfirmed from intraoperative pathology. The other 37 wrists had normal DRUJ. Among the three methods, the epicenter method had similar sensitivity to Mino's criteria and the congruity method. However, the epicenter method had much better specificity than Mino's criteria and the congruity method. CONCLUSIONS: For accurate diagnosis of subluxation of the DRUJ, CT scan through the symptomatic DRUJ in neutral rotation, active full supination, active full pronation and analysis with the epicenter method are recommended.