Lack of correlation between ulnar variance and carpal bone angles on lateral radiographs in normal wrists.

It has been proposed that negative ulnar variance is a predisposing factor to development of posttraumatic carpal ligamentous instability. However, this implies that no correlation exists between ulnar variance and carpal bone angles in the normal wrist. Carpal bone angles on lateral wrist radiographs and ulnar variance were measured in a series of 75 normal wrists. The mean ulnar variance was -0.03 mm (SD 1.56, range -5 to 5). The correlation coefficients were 0.06, -0.11, and -0.05 between the ulnar variance, and radiolunate, radioscaphoid, and scapholunate angles, respectively. A correlation between the carpal angles on lateral wrist radiographs, and ulnar variance in normal wrists could not be demonstrated, suggesting that the presence of negative ulnar variance may serve as an impartial clue to the presence of ligamentous instability.