bone age test

A bone age test is performed to determine the relative maturity of a child's skeletal system compared to large numbers of other children of the same chronologic age. It gives the doctor and parents some idea of how fast or slowly growth is progressing, and what the likely ultimate adult height of the child will be.

When a child is born, he or she can naturally be expected to grow in size until maturity is reached. Increase in size involves not only increase in body mass, but of course increase in length of the skeletal bones. The child will grow in stature by increase in bone length until maturity is reached, usually in the late teens or early twenties.

Of course all children grow at different rates, but their growth rates tend to be distributed in the classic "bell curve" distribution. Bone age tests are performed by xraying several growth centers - usually wrist and elbow - and comparing the xrays to pictures in a book of standards. The pictures are divided into normals for boys and girls in three month intervals.

Bone age tests are often used to help determine if endocrine (glandular) abnormalities are present or should be suspected. Low thyroid hormone levels or deficiencies of growth hormone delay skeletal maturation and thus the bone age; adrenogenital syndrome advances the maturation (and leads to rapid growth and ultimately reduced height). Probably the most common use in office practice is to determine how much growth potential a short child really has. If a child is, say, 5 years old, but has a bone age of 3-1/2 years, and is otherwise healthy, we can often identify him as a "slow grower" and reassure the parents that although he will go through puberty a bit late, he will grow longer than his peers and will attain a greater adult height than would be predicted by looking at him today.

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