A Study of Skeletal Maturation in the Hand-Wrist Radiograph of Twins

Abstract

Bone ages were assessed using the hand-wrist r radiograph of 31 monozygotic twin pairs and 15 dizygotic twin pairs. Assessments were made on the right and left hand on two separate occasions. The method of assessment used was a modification of the Greulich and Pyle method. The measurement error for the assessments was 3.8 months and 4.1 months for the left and right hand respectively. No asymmetry was demonstrated between right and left sides. The four assessments were averaged to obtain a single bone age assessment for each individual. The ratio of the epiphyseal-metaphyseal width for the radius and ulna was proposed as a quantitative measurement which closely corresponds with the subjective bone age assessment. Correlation coefficients ranging from .84 to .90 were reported for the epiphyseal-metaphyseal ratios with bone age assessments. When the ratios were analyzed with respect to sex, correlation coefficients ranging from .89 to .94 were reported. The correlation of the ratios with bone age assessments was consistently greater in males than females. As tested by the F statistic, a significant amount of variation in bone age and ulna epiphyseal-metaphyseal ratio could be attributed to the heritability fraction. Using the Holzinger formula, 82% of the bone age assessment and 88% of the ulna ratio could be attributed to the heritability fraction.