Displacement of the distal radioulnar joint of clinically symptom-free patients.

There are three methods for evaluation of dislocation of the distal radioulnar joint using computed tomography: the radioulnar line method, the epicenter method, and the congruity method. However, some patients who are clinically symptom-free have abnormal findings from computed tomography of the distal radioulnar joint according to the aforementioned criteria. In addition, these methods are qualitative, not quantitative definitions. Forty patients were included in this study. Computed tomography scans of the wrists were done. The variation of displacement of the distal radioulnar joint was measured. By the epicenter method, the 95% confidence interval (mean +/- 1.96 standard error) was from 0.0026 to 0.1114 in supination and from -0.1171 to 0.0446 in pronation. By the radioulnar line method, the 95% confidence interval was from 0.0026 to 0.0479 in supination and from -0.0065 to 0.0745 in pronation. By the modified radioulnar line method, the 95% confidence interval was from 0.1778 to 0.2752 in supination and from 0.0990 to 0.2310 in pronation. There was a wide range of the displacement of the distal radioulnar joint in patients with clinically normal wrists. The results can be regarded as reference points for normal variation of the distal radioulnar joint. This can help to differentiate the causes of internal derangement of the wrist.