The GRIT: a quantitative measure of ulnar impaction syndrome.

The gripping rotatory impaction test (GRIT) is performed with a standard grip dynamometer and provides a quantitative measure for identifying ulnar impaction. The purpose of this study was to determine whether patients with unilateral ulnar impaction syndrome (UIS) have a GRIT ratio on the involved side greater than 1.0 while the GRIT ratio on the uninvolved side is no different from 1.0. Twenty-four patients with unilateral UIS were tested with the GRIT on both the symptomatic, involved side and the asymptomatic, uninvolved side. The GRIT was performed with a standard grip dynamometer, and testing alternated between each patient's involved and uninvolved sides, with the wrist in the neutral, supinated, and pronated positions, in that order. The GRIT ratio on the involved side, at 1.37, was significantly greater than 1.0, while the GRIT ratio on the uninvolved side, at 1.03, was not significantly different from 1.0. The GRIT ratio is a quantitative measure that identifies UIS and can be used as an adjunct to imaging studies and qualitative clinical tests for UIS. The GRIT may also be helpful in determining which patients with UIS might benefit from surgical ulnar shortening.