First of all, it is important to explain what is bone age? Bone age (BA), as the name implies, is the abbreviation for bone age, which is the age of bones. It is a comparison of the actual development of a child’s bones with the standard developmental level, and is a comparative value of the developmental age. Why is it important to measure bone age? Bone age, to a large extent, represents the true developmental level of a child, and therefore, in practical clinical applications, it is often more accurate to use bone age to determine the maturity and development of the human body than the actual age. Doctors can generally determine the age of bone by observing the degree of development of the metacarpal phalanges, carpal bones and the ossification center of the lower end of the radius and ulna of the left hand based on the orthopantomographs taken of the left hand, this is because most people (except left-handed people) use the left hand much less frequently compared to the right hand, and theoretically, the infrequently used hand grows more slowly, and the commonly used hand will artificially increase the growth age of the bone, so people generally use the left hand to measure Therefore, people generally use the left hand to measure the bone age, and what is measured in this way is generally considered to be the minimum value of bone age. The bone age of a normal person is generally consistent with the physiological age, or very similar; however, in a disease state, it may be very different. For example, in children with complete growth hormone deficiency, the bone age is often younger than the age, and in some cases, the bone age is 2-3 years or more younger than the actual age; while in precocious puberty, the bone age of some children is greater than the actual age, and the physiological age may be 8 years old, while the bone age may have reached or even exceeded 10 years old. Therefore, for height and development monitoring, it is very important to measure the bone age. If you notice that your child is shorter than his or her age, or that his or her growth rate has slowed down in the past year, or if you notice that a girl has recently developed breasts or menstruated, or a boy has grown a larynx or changed his voice, you should see your pediatrician for a bone age film to determine your child’s skeletal maturity, and then, based on the results of the bone age film, you can determine if further tests and interventions are needed.