Assessment of distal radioulnar joint instability after distal radius fracture: comparison of computed tomography and clinical examination results.

PURPOSE: To compare computed tomography (CT) and clinical stress test findings in terms of the assessment of distal radioulnar joint (DRUJ) instability after distal radius fracture.

METHODS: Thirty-four patients with a healed unilateral distal radius fracture were evaluated after a mean follow-up period of 18 months. Stress test and CT were performed to detect DRUJ instability. Three CT methods were used: the modified radioulnar line, the epicenter, and the radioulnar ratio methods. The results of CT assessments were compared with stress test findings using kappa statistics. Relationships between DRUJ instability and the radiographic parameters of volar tilt, radial inclination, and radial shortening were analyzed.

RESULTS: Twelve patients were considered to have DRUJ instability based on the stress test. DRUJ instability was diagnosed in 15, 8, and 11 patients by the modified radioulnar line, the epicenter, and the radioulnar ratio methods, respectively. Reliability analysis of stress test and CT results showed moderate or fair agreement (kappa value: .33 for the modified radioulnar line, .56 for the epicenter, .41 for the radioulnar ratio). DRUJ instability diagnosed by the stress test and by CT showed no statistical correlation with radiographic parameters, but instability determined by CT appeared to be related to dorsal tilt deformity.

CONCLUSIONS: After distal radius fracture, CT assessments of DRUJ instability were found to be influenced by residual deformities, such as dorsal tilt, but not well correlated with stress test findings. Although CT assessments are objective, CT scans primarily show alterations of DRUJ alignment and have several risks of bias in patients with a prior distal radius fracture.