A study on the RUS-CHN bone age assessment method in adolescents and children from the Suzhou region

The RUS-CHN method, part of the China-05 standard, is widely used in China. However, its performance may vary across regions due to socioeconomic and nutritional factors. This study aimed to clinically validate the RUS-CHN method against the Greulich-Pyle (G-P) atlas in a cohort from the developed Suzhou region.

We conducted a cross-sectional study of 271 children. Left-hand radiographs were independently assessed by two experienced raters using both the G-P and RUS-CHN methods. Statistical analyses compared the distributions, correlations, and specific bone scores derived from the two methods.

The median age of the 271 enrolled children was 12.08 years, with a mean height of 155.9 ± 7.4 cm and a median BMI of 19.4. Compared to the G-P method, the RUS-CHN method yielded a more concentrated bone age distribution with a smaller interquartile range. Based on the absolute value of Spearman's correlation coefficient, in the overall cohort, the radial score showed the highest correlation with the total RUS-CHN bone age for boys (0.661), followed by the first metacarpal (0.652) and the proximal phalanx of the first finger (0.646). For girls, the third metacarpal score correlated most strongly (0.698), followed by the proximal phalanx of the third finger (0.660) and the proximal phalanx of the fifth finger (0.659). According to the G-P method, 119 children (43.91%) had normal development, 7 (2.58%) were delayed, and 145 (53.51%) were advanced. In contrast, the RUS-CHN method classified 92 children (33.95%) as normal, 4 (1.48%) as delayed, and 175 (64.58%) as advanced. Over 60% of children exhibited advanced bone development, with girls comprising more than half of this group. Children with advanced development had a lower median visit age (11.2 years) and a higher BMI than those with normal or delayed development. In the normal development group, for boys, the first metacarpal score showed the highest correlation with RUS-CHN bone age (0.727), followed by the radius (0.709) and the proximal phalanx of the third finger (0.706). For girls in this group, the third metacarpal score correlated highest (0.787), followed by the fifth metacarpal (0.741) and the middle phalanx of the third finger (0.684). In the advanced development group, for boys, the proximal phalanx of the first finger had the highest correlation (0.654), followed by the first metacarpal (0.649) and the radius (0.647). For advanced girls, the proximal phalanx of the fifth finger correlated most strongly (0.684), followed by the proximal phalanx of the third finger (0.661) and the third metacarpal (0.651).

The RUS-CHN scoring method is applicable for bone age assessment in children from the Suzhou region. Likely influenced by socioeconomic factors, over 60% of the children in this region were classified as having advanced bone development. Within this scoring system, the evaluation weight of different bones varies by gender and developmental status. Focusing on the maturity of key correlating bones may be more critical for identifying developmental abnormalities.