Orthodontic treatment for malocclusion moves faster during growth spurts. In general, children have a pattern of fast growth, followed by slow growth in late childhood, and then another growth spurt in the teen years. Because children start this pattern at different ages, chronological age (real age) doesn't indicate a child's stage of development very well. Some children just develop faster or slower than others.

The hand-wrist radiograph, or X-ray image of the wrist bones, can help pinpoint a child's skeletal age. Wrist bones develop to adult size in a clear pattern. This has allowed experts to make a picture atlas of wrist bones in various development stages. Orthodontists can compare a hand-wrist radiograph with the atlas and find out a child’s skeletal age. With this data, an orthodontist predicts the next growth spurt and makes a treatment plan that takes advantage of the timing.