EVALUATION OF THE SKELETAL-AGE METHOD OF ESTIMATING CHILDREN'S DEVELOPMENT
Authors: Mainland Donald 
Published: December 2021

The inspectional method of estimating children's skeletal ages from an atlas of standard films is based on the fact that increase of size (e.g., of a carpel bone or epiphysis) is not equivalent to maturation. The deficiencies of the inspectional method, however, render measurement methods very desirable.
After ossific centers have appeared, further changes (development or maturation) are largely expressible as changes in shape or proportions, and are therefore measurable; but, to avoid the complexity of expressing shape by measurement, the present study started from the premise that change in shape is associated (although to an unknown degree) with increase in linear dimensions.
On all the reproductions in the Todd and Greulich-Pyle hand atlases, and on Todd's intermediates (film-reproductions of roentgenograms used in the atlas), simple linear measurements were made on four maturity indicators: radius epiphysis, capitate, metacarpal III epiphysis, and the epiphysis of the proximal phalanx of digit III.
To express the relationship between age and the size of each indicator, moving-average curves were developed (usually by 5-point averages). To obtain a "measurement estimate" of the skeletal age of any film, the age estimates derived from the curves for the four indicators were averaged, giving equal weight to each indicator.
For the Todd intermediates a more complicated method of estimating age from indicator sizes was also used—a multiple regression equation, which automatically allotted an appropriate weight to each indicator and permitted adjustment for general hand (or bone) size where required (phalanx shaft width as an adjustment for epiphysis width).
The ages estimated by measurement (moving-average and regression methods) were compared with inspectional estimates, from Todd and Greulich-Pyle atlases, on three series of roentgenograms comprising a total of more than 250 films from 190 children of ages 2 to 14½ years. The conclusions were:
1. For the group-study of children between the age when ossific centers have appeared and the age of incipient epiphyseal union the measurement estimates of skeletal age would be equivalent to inspectional estimates in comparing (a) average skeletal ages, (b) inter-child variation in skeletal age, and (c) average progress (average gain in skeletal age).
2. Because even "actual-size" reproduction in the preparation of an atlas causes a change in size, the measurement method, unless based on intermediates, does not permit reliable comparison, even of groups, with standard (atlas) children. This drawback could be removed by publishing, instead of an atlas, tables of measurement-age equivalents derived from current or future series of standard children's roentgenograms (actual films or intermediates) with some reproductions for guidance in measurement.
3. In the assessment of an individual child's skeletal age status or progress the differences between inspectional and measurement ages vary so greatly from film to film that the measurement method seems to be of little use; but for this purpose the inspectional method itself is very crude.