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.