Changes in ulnar variance in relation to forearm rotation and grip.

We studied radiographs of the wrists of 120 healthy volunteers in order to determine the normal range of ulnar variance. They had been taken in various positions under both unloaded (static) and loaded (dynamic) conditions. Pronation posteroanterior, supination anteroposterior and neutral posteroanterior views were taken of each wrist before and during a maximum grip under identical conditions. The mean normal ulnar variance in neutral rotation was +0.74+/-1.46 mm, a value which was significantly lower in males than in females. We found negative variance in 26% of cases. We measured maximum ulnar variance (UVmax +1.52+/-1.56 mm) when gripping in pronation and minimum ulnar variance (UVmin +0.19+/-1.43 mm) when relaxed in supination. We subtracted UVmin from UVmax to calculate a mean maximum dynamic change in ulnar variance of 1.34+/-0.53 mm. We consider this database of normal values to be useful for both the diagnosis and treatment of conditions related to discrepancy in radio-ulnar length and for clinical research.