The importance of the pronated grip x-ray view in evaluating ulnar variance.

Although dynamic increases in ulnar variance may accompany functional activity, radiographic assessment of ulnar variance traditionally has used a neutral rotation x-ray of the wrist that provides an image of the radioulnar length with the wrist unloaded. Such a view may underestimate variance in wrists in which power grip and pronation result in significant proximal migration of the radius. This study investigates the effect of a maximum grip effort in combination with forearm pronation on ulnar variance in 22 patients who presented with ulnar wrist pain. The pronated grip x-ray view resulted in statistically significant increases in ulnar variance. Preoperative ulnar variance should be measured using both neutral rotation and pronated grip x-rays before selecting treatment for causes of ulnar wrist pain that are affected by radioulnar length so that dynamic increases in ulnar variance are considered when operative treatment is necessary. Copyright 2000 by the American Society for Surgery of the Hand.