Clinical and experimental studies on ulnar ray deficiency.

Thirteen cases with ulnar ray deficiency and thirty-three cases with radial ray deficiency were analysed. The differences of these two anomalies are not only affected parts, but also clinical features. The severity of absence of the fingers in ulnar deficiency was classified into five types. The degree of ulnar arrest was closely related to the severity of deficiency of the fingers and also to abnormalities of the elbow joint. Ulnar deficiency was induced by myleran in rat fetuses. The features of ulnar ray deficiency in rats were the same as in humans. The critical period of ulnar deficiency was earlier than that of other anomalies and it corresponds to the period of a high mortality rate of fetuses. This could be the reason why ulnar deficiency does not appear as often as other anomalies.