Comparison of TW1 and TW2 skeletal age differences in American black and white and in Mexican children 6-13 years of age.

Differences in Tanner-Whitehouse (TW) skeletal ages as derived from the original (TW1) and revised (TW2) systems were compared in three ethnically different samples of children 6-13 years of age: mixed longitudinal samples of American White and Black children for Philadelphia, and a cross-sectional samples of Mexican children from Oaxaca in southern Mexico. TW2 skeletal ages are, on average, consistently lower than TW1 skeletal ages. Within a given chronological age and sex group, the differences are similar in terms of means and variation about the means in better-off children, both black and White in Philadelphia and in disadvantaged Mexican children.