Ulnar variance in Kienböck's disease.

Forty four patients with forty seven wrists suffering from Kienböck's disease were re-examined. The mean observation time was 20.5 years. In all forty seven wrists the treatment had been immobilization. Using a standard X-ray projection, and a reliable method of ulnar variance measuring, the ulnar variance was determined by three observers independently. Comparing the result with the ulnar variance in normal wrists we found the so-called "ulnar minus variant" overrepresented in patients with Kienböck's disease. However, comparing X-rays taken at the time of diagnosis with X-rays at re-examination, we found in eight out of forty seven wrists that a subchondral bone formation in the distal radium opposite the lunate bone had taken place. This bone formation will tend to enhance the negative value of ulnar variance measurements, and suggests an explanation of the overrepresentation of "ulnar minus variants" in Kienböck's disease. Excluding these eight wrists from the material and comparing the mean ulnar variance value in the remaining thirty nine wrists with the mean value in normal wrists no statistical difference was shown. Based on these observations it seems unlikely that the "ulnar minus variant" has any bearing on the cause of Kienböck's disease.