Objective: The study analyzed the relationship between skeletal age (SA) and the difference between skeletal and chronological ages (SA-CA) and body size among growth-stunted and well-nourished children.
Methods and materials: Tanner-Whitehouse 2 (TW2) 20 bone, radius-ulna-short (RUS) bone, and carpal SAs were analyzed in three cross-sectional samples of school children aged 6-13 years: Mestizo children (n = 396) from the city of Oaxaca, southern Mexico, and American Black (n = 570) and White (n = 432) from Philadelphia. The Oaxaca children were mild-to-moderately undernourished while the Philadelphia children were well nourished. The total sample included 1398 radiographs assessed with the Tanner-Whitehouse protocol by a single, experienced rater. Maturity scores were converted to TW2 20 bone, RUS and carpal SAs.
Results: Correlations of SA and SA-CA differences with body dimensions (height, sitting height, leg length, weight, triceps skinfold, arm and estimated midarm muscle circumferences) were consistent and approximately equal in magnitude for the well-nourished samples but were different among Oaxaca children. SAs of Philadelphia children were significantly more highly correlated with body dimensions than were SA-CA differences compared to Oaxaca Mestizo children. Patterns of RUS and carpal SA correlations with body size (height, sitting height, and leg length) in Oaxaca children were different from the Philadelphia samples. Oaxaca children tended to have advanced RUS SA and delayed carpal SA.
Conclusion: Long bone complexes mature earlier than round bone complexes in Oaxaca children compared to Philadelphia Black and White children, resulting in short stature in Oaxaca children. Results suggest a gene-environment interaction effect on the program for skeletal growth and maturation in undernourished Oaxaca children compared to well-nourished Black and White children from Philadelphia.