Distal radioulnar joint instability with three different injury patterns assessed by three-dimensional C-arm scans: a cadaveric study.

The aim of this study was to establish a radiographic method for detecting distal radioulnar joint instability intraoperatively. We created three successive instabilities in 12 intact Thiel-fixed upper limb specimens: lesion of the triangular fibrocartilage complex, Galeazzi injury and Essex-Lopresti injury. We made three-dimensional scans of the wrists in pronation and supination with a mobile C-arm. We used four validated measurement methods to quantify ulnar migration in the standard axial planes: the radioulnar line method, the subluxation ratio method, the epicentre method and the radioulnar ratio method. All types of instability showed significantly increased migration of the ulna compared with the control group. The subluxation ratio and the radioulnar ratio methods showed the highest sensitivity and specificity in detecting the instabilities. We conclude that these two methods are feasible for radiographically assessing distal radioulnar joint instability. Instability may be assumed if the migration of the ulna in the sigmoid notch is at least 45% of the length of the sigmoid notch, in which case wire transfixation of the distal radioulnar joint is advised.