Ulnar variance and Kienböck's disease. An investigation in Taiwan.

The correlation between negative ulnar variance and the occurrence of Kienböck's disease was evaluated in Taiwan. Two groups of subjects were studied. The first group consisted of 1000 normal subjects and the second of 18 patients with Kienböck's disease. Student's t-test was used to evaluate the significance of the difference between this and other published series. The mean was 0.313 mm in Group 1 and -1.222 mm in Group 2. The percentage with significant negative ulnar variance (the distal ulnar was at least 2 mm shorter than the radius) was 6.0% in Group 1 and 55.6% in Group 2. The difference between the two groups was significant. The mean ulnar variance of normal subjects in Taiwan differed significantly from the variance in Swedes and American blacks but not American whites. In Chinese patients with Kienböck's disease, the ulnar variance was predominantly negative, and the distribution of ulnar variance was similar to that of Swedish or American white patients. This study confirmed the association between negative ulnar variance and the occurrence of Kienböck's disease. This supports Hultén's hypothesis that negative ulnar variance may predispose certain individuals to the occurrence of Kienböck's disease.