What is bone age and what does it show?
A simple X-ray of the hand shows how mature the bones are. What does it say, and what does it not say?
Age on paper says how old a child is. Bone age says what age of child the bones look like. The two are not always the same.
How is the picture taken?
Usually a simple X-ray of the left wrist and hand is taken. The doctor compares the shape of the bones and the growth plates with standard examples. A growth plate is a strip of cartilage near the end of a bone, and while it is open the bone can get longer.
What does the number mean?
- Bone age younger than real age: the bones have more time to grow. This is seen in late development, but also in an underactive thyroid and growth hormone deficiency.
- About equal: seen in many healthy children and in family short stature.
- Bone age older than real age: the bones are maturing early and growth may finish sooner. This is seen in early puberty and sometimes in obesity.
What does it not say?
Bone age alone is not a diagnosis. One picture without a growth chart and an examination says little. An estimate of final height is only an approximate range. A small gap between the two ages can be normal, and doctors read films slightly differently.
How often?
Only when the doctor sees a need. Repeating it too soon usually adds nothing. Keep earlier films and bring them, because comparing them is more useful than one new picture.