Background: Radiocarpal dislocations represent a high-energy wrist injury that can occur with or without concomitant fractures about the wrist. Poor outcomes are often due to radiocarpal instability and secondary ulnar translation. The purpose of this cadaveric study is to determine if there is any difference in the radiographic parameters in a wrist dislocation model given the different location of distal fixation. Methods: Ten paired fresh cadaver upper extremities were fluoroscopically evaluated with posterior-anterior (PA) and lateral views. We created a radiocarpal dislocation model and applied a dorsal bridge plate to either the second or third metacarpal. Repeat PA and lateral fluoroscopic views were obtained for evaluation of radial inclination, radial height, volar tilt, ulnar variance, radiolunate angle, radioscaphoid angle, scapholunate angle, radial rotation index, and four indices for ulnar translation (Taleisnik, Gilula, McMurtry, and Chamay). Results: Bridge plate application to the second metacarpal resulted in a significantly greater incidence of ulnar translation compared to the third metacarpal. Application to either metacarpal resulted in extension of the carpus relative to the radius. Conclusions: A more anatomic radiocarpal relationship was restored more often when distal fixation of the dorsal wrist-spanning bridge plate was applied to the third metacarpal. Further investigation is warranted to determine clinical relevance of these findings in conjunction with clinical and radiographic outcomes.
Keywords: anatomy; bridge plate; diagnosis; distal fixation; fracture/dislocation; radiocarpal; radiocarpal dislocation; ulnar translation; wrist.