Bone age assessments: What they can tell you about growth

Puberty is a time for rapid growth and development for nearly every system in the body—not just the reproductive system. Growth spurts occur throughout childhood but are usually more pronounced at the onset of puberty.

Bone growth assessments can be useful when it comes to gauging growth rates, especially when it comes to understanding¹:

• How much a child is expected to grow
• When a child will enter puberty
• What the child’s final height will be

Pediatricians can look to a child’s parents for some of this information, but more specialized assessments can help, particularly if there is a concern for any disorders or conditions that may affect growth, development, or bone health.

Katherine Kutney, MD, a pediatric endocrinologist at Rainbow Babies and Children’s Hospital in Cleveland, Ohio, said bone age assessments are typically done with an x-ray of the left hand. Bone age is measured in years and assigned by a trained radiologist or endocrinologist by comparing the child’s measurements with existing standards. The most common measurement standards used for bone age are the Greulich and Pyle Atlas² and the Tanner-Whitehouse³ assessments.⁴

Bone age assessments can provide pediatricians with a rough estimate of when a child will enter puberty, Kutney stated. A child with advanced bone age is likely to reach this milestone earlier, whereas a child with delayed bone age will probably enter puberty later than normal.

There are extremes to be mindful of, Kutney added.

“Any child with bone age more than 2 years advanced or delayed, or whose growth pattern deviates from their genetic potential should be referred to endocrinology for assessment,” she noted.

Genetic potential is determined by mid-parental height, which is calculated by averaging sex-adjusted parental heights.
Kutney shared the following examples.

• For males, one takes the maternal height and adds 5 inches or 13 centimeters, and averages this value with the paternal height to obtain the mid-parental height.
• For females, one takes the paternal height and subtracts 5 inches or 13 centimeters, and averages this value with the maternal height to obtain the mid-parental height.

Most children will achieve a final height within 4 inches of the mid-parental height estimate, she said.

“This may not be the case if the maternal and paternal heights are discordant, or if the child takes more after 1 parent,” Kutney added.

Puberty timing plays a big role in growth, too.

For a child with “average” puberty timing, Kutney said pediatricians should expect the child to follow the height percentile consistent with their final adult height. For example if a girl will have a normal timed puberty and a final height of 5’5”, she would be expected to grow along the 50th percentile through childhood.

When a child experiences “earlier than normal” puberty timing, the child would be expected to follow a height percentile above their final adult height percentile. This means that a girl who will have a final adult height of 5’5” but will undergo puberty earlier than average may grow along the 80th percentile in early childhood. However, she will stop growing earlier than her peers to attain a final adult height at the 50th percentile, Kutney noted.

Finally, children with “later than normal” puberty timing, are expected to grow along a height percentile below their final adult height, but continue growing longer than their peers. This means a girl who falls into this category may grow along the 25th percentile in childhood but continue growing longer than other children due to delayed puberty and have a final height at the 50th percentile.

Deviations from these patterns, or other signs of delayed bone growth need to be investigated by a specialist, Kutney stated. A number of conditions could contribute to delayed bone age, including:

• Hypothyroidism
• Growth hormone deficiency
• Other hormonal disorders
• Nutritional deficiency
• Intestinal inflammatory chronic conditions
• Celiac disease
• Cystic fibrosis
• Other chronic inflammatory states
• Immunodeficiency
• Cardiac diseases
• Chronic kidney diseases
• Liver disease
• Psychosocial stress or abuse
• Trisomy 21
• Turner syndrome
• Russell-Silver syndrome

“Any child crossing up or down percentiles in childhood—after age 3 years and before puberty—should be referred,” Kutney said.

References

1. Nemours Kids Health. X-ray exam: bone age study. Accessed November 22, 2021.
 https://kidshealth.org/en/parents/xray-bone-age.html

2. Alshamrani K, Messina F, Offiah AC. Is the Greulich and Pyle atlas applicable to all ethnicities? a systematic review and meta-analysis. Eur Radiol. 2019;29(6):2910-2923. doi:10.1007/s00330-018-5792-5

3. Cox LA. Tanner-Whitehouse method of assessing skeletal maturity: problems and common errors. Horm Res. 1996;45:53–55. doi: 10.1159/000184848.

4. Satoh M. Bone age: assessment methods and clinical applications. Clin Pediatr Endocrinol. 2015;24(4):143-152. doi:10.1297/cpe.24.143.

5. Cavallo F, Mohn A, Chiarelli F, Giannini C. Evaluation of bone age in children: a mini review. Front Pediatr. March 12, 2021. 9:21. doi: 10.3389/fped.2021.580314.