Children have two different expressions of age during growth and development, namely, life age (or actual age) and biological age, with the latter usually expressed as the level of bone developmental maturity. Due to the influence of many factors such as genetics, environment, nutrition, exercise and disease, people’s life age and developmental level are often inconsistent, so it is evident that life age does not truly reflect the degree of individual maturity; however, the level of bone development expresses both the role of parental genetic factors and contains the influence of various environmental factors, and bone development runs through the entire growth and development. Therefore, the use of bone age, which is closely related to growth and development, is a more realistic indicator of the maturity of a child’s growth and development, and it is generally considered to be the most accurate, simple and reliable monitoring index. The bone age of a child is generally determined by comparing the maturity of some of the bones (fingers, palm, wrist) with the bone age of a normal child in the same area.
There are several methods for determining bone age, such as the metacarpal, finger and wrist bone mapping method and the bone scoring method. The atlas method is mostly used clinically, and it is more convenient. The scoring method is a finer scoring method, which is suitable for longitudinal comparison of individuals or inter-individual comparison.