The Effect of Power Grip on Ulnar Variance A Computed Tomography Study of the Wrist and Elbow.

Although an increase in ulnar variance with power grip is well documented in the medical literature, there is a paucity of information concerning its mechanism. This concept was examined in five healthy individuals using computed tomography of their wrists and elbows. Images were obtained of both joints in the resting position and with maximum power grip. Ulnar variance at the wrist increased an average of 0.64 mm (range: 0.3 to 1.2 mm). While the ulnohumeral joint remained unchanged, the radiocapitellar distance shortened an average of 0.62 mm (range: 0.3 to 1.0 mm; p = 0.03), which correlated directly with the change at the wrist. Our study showed that the increase in ulnar variance with grip was due to proximal shift of the radius and not to any distal migration of the ulna, which may have clinical implications in reconstruction or arthroplasty of the elbow.