LAUSR

BACKGROUND The purpose of this study was to quantify the in vivo displacement of bilateral distal radioulnar joints (DRUJs) in resisted pronosupination. We hypothesize that this will demonstrate no appreciable difference between the left and right DRUJ, thus validating the concept of using the uninjured wrist as a control for physical examination as well as dynamic imaging studies. METHODS Thirty-two participants without a history of wrist pathology underwent a dynamic computed tomography (CT) protocol evaluating bilateral forearm rotation in neutral forearm rotation, 60° pronation, and 60° supination, including maximal isometric muscle loading. The DRUJ alignment, specifically the absolute degree and direction of subluxation of the ulna relative to the sigmoid notch, was then assessed using a modification of the radioulnar line method. RESULTS There was no significant difference in the mean displacement when comparing the right and left sides in neutral, pronation, or supination. The mean displacement was also compared between male and female patients, and there was no statistically significant difference in absolute displacement in neutral (male 0.99 mm vs female 1.38 mm) or supination (male -0.57 mm vs female -0.23 mm). However, the difference in pronation was statistically significant (male 2.69 mm vs female 3.26 mm). Of the 192 sequences, the measurements of displacement of the authors were within 1 mm 86% of the time (166 of 192). CONCLUSIONS Dynamic CT of bilateral DRUJs in resisted pronation, supination, and neutral demonstrated symmetry between the right and left DRUJ, supporting the concept of using the contralateral side as a control to identify instability in an injured wrist.