Changes in Ulnar Variance in Relation to Forearm Rotation and Grip

Author(s): Jung JM, Baek GH, Lee YH, Chung MS

Source: J Bone Joint Surg 83-B:1029-1033, 2001

Summary:

One hundred and twenty healthy volunteers were studied to determine normal ulnar varience in a variety of positions and loading conditions. Forearm rotation and grip-related changes were used as variables. The method of perpendiculars was used to assess ulnar variance and a jig used to control position. A database of normal ulnar variance is presented. Ulnar variance increased with pronation and grip, as expected. The patient was instructed to grip tightly and degree of force was not considered in the calculations. Mean ulnar variance was 0.74 „b 1.5 mm. Negative ulnar variance was found in 26% of individuals.

This review generates normal values for ulnar variance in different positions of forearm rotation and grip. However, the data may be limited to Koreans, who appear to have higher variance measurements than other nationalities (Chinese, and Japanese). The authors indicate that the amount of ulna resected in ulnar impaction syndrome should be the difference between the resting ulnar variance and the value calculated in pronation and power grip. This may be true, although biomechanical studies indication that a resection of 2.5 mm usually results in a significant reduction in ulnar force from 20 to 5%.

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