Skeletal age, referred to as bone age, is determined by the degree of skeletal calcification in children. Bone age is a more accurate reflection of the level of development from birth to full maturity.
Bone age is generally determined by taking an x-ray of the left wrist because it concentrates a large number of long, short and round bones and reflects the growth and maturity of the whole body. The number and size of the ossification centers, the morphological changes of the ossification centers and epiphyses, and the healing of the epiphyses and diaphyses are the three main points to determine the degree of bone calcification.
The growth potential of the child can also be determined by the width of the cartilage plate of the long bone epiphysis on the X-ray. The narrowing of the cartilage plate of the metaphysis of the terminal phalanx and the near fusion of the diaphysis with the epiphysis mark the end of the rapid growth period and the beginning of the slowing down of the growth period. When the cartilage plate of the epiphysis of the radius and ulna disappears, the long bones of the limbs no longer grow, i.e., the growth of height has basically stopped, and at most the spine, i.e., the sitting height, can still grow by 1-2 cm.
The use of bone age to infer development, thus reflecting the state of physical growth and development, helps to understand the potential of children’s height development. For example, in an industry with special requirements for height, two 11-year-old girls, both 147 cm tall and otherwise identical, are confronted at the same time. However, the bone age of one of the girls is only 10 years old, indicating that there is still a considerable amount of time before the epiphysis heals. The other had a bone age of 13 years, which is close to the average bone age level of girls at menarche, and her height was not expected to increase significantly, so the former girl was chosen as more likely to be enrolled.
Bone age has a greater impact on outcome when it comes to interventional treatment for dwarfism, and overall the younger the bone age, the better the treatment outcome. Once the epiphysis is closed, there is essentially not much hope of growing taller.