Frequency of Clinodactyly in Children between the ages of 5 and 12

Abstract

SummaryA study of fingers characteristics was made on 1387 school children.1. Clinodactyly (5th finger) with an angle of inclination of 21.3 ±0.7 degrees, was found in 15.2% of the male and 8.06% of the female white children between the ages of 5 and 12. These represent the heterozygotes of the population, Cc, while the extreme form of clinodactyly, with an angle of inclination of over 30 degrees, most likely represents the homozygotes of the population, CC.2. Curved index finger (2nd) occurs less frequently than clinodactyly (in 2.22% of the group studied).3. Flexed little finger (5th) occurs least often, about 1 in 320.4. Bilateral penetrance ratio has been defined. Clinodactyly has a bilateral penetrance ratio of 0.77 in males and 0.64 in females. The curved index finger has a bilateral penetrance ratio of approximately 0.75.5. Clinodactyly also occurs in Negro children.6. An instrument is described for measuring the angle of inclination of clinodacyly.