To evaluate the applicability of bone age (BA) assessment methods and to investigate the difference between BA and chronological age (CA) based on the data of children in rural areas of Beijing.

A total of 412 healthy children (226 boys, 186 girls) with the age 8.6 (6.8, 10.3) years old were included in this study. The data of the prospective study were from a subgroup of the project "National Nutrition and Health Systematic Survey for 0-18 Years Old Children in China", which included children with age of 3-12 years old in Beijing rural areas. The non-dominant hand-wrist radiographs of all participants were obtained in April 2021. The Dr.Wise BA detection and analysis system was used to assess the BA according to the Tanner Whitehouse 3 (TW3) radius-ulna-short bone score (TW3-RUS), TW3 carpal bone score (TW3-Carpal), China-05 TW3-Chinese RUS (TW3-C RUS), China-05 TW3-Chinese carpal (TW3-C Carpal), and Greulich-Pyle (G-P) standards. The cases were stratified by the sex and different CA in the statistical analysis. The estimated BA obtained using different methods were compared with the CA using Wilcoxon signed ranks test.

The sex-stratified results showed that no significant difference was found between the estimated BA using G-P standards and CA in boys (Z=-0.694, P=0.488), while all the other estimated BA results were statistically significantly higher than CA (P<0.05). Stratified by both sex and CA, the estimated BA using G-P standards in 4-6 years old boy groups, as well as the estimated BA using TW3-Carpal and TW3-C Carpal standards in 11-12 years old girl groups were lower than CA, while in the other groups, the estimated BA were higher than CA.

There were varying degrees of deviations in the BA estimations using TW3, China 05, and G-P methods for children in rural areas of Beijing. It is imperative to establish a new standard for the BA evaluation of the contemporary Chinese children.

Age determination by skeleton; Radiography