What does a bone age -0.9 standard deviations from the mean indicate and how should it be managed?

Interpretation and Management of Bone Age -0.9 Standard Deviations from Mean

A bone age of -0.9 standard deviations from the mean is within normal limits and generally requires no specific intervention, as it falls within the normal range of bone age variation (between -2.0 and +2.0 standard deviations).

Understanding Bone Age Assessment

Bone age is a measure of skeletal maturity determined by radiographic examination of the left wrist. It represents the degree of bone maturation compared to chronological age and is expressed as standard deviations from the mean.

• Normal range: Generally between -2.0 and +2.0 standard deviations from the mean
• Delayed bone age: Below -2.0 standard deviations
• Advanced bone age: Above +2.0 standard deviations

Clinical Significance of -0.9 SD Bone Age

A bone age of -0.9 SD indicates:

• Mild delay in skeletal maturation that is still within normal limits
• No immediate clinical concern requiring intervention
• Falls within expected variation of normal bone development

Assessment Considerations

When evaluating bone age results:

1. Radiographic assessment: Bone age is typically determined using hand and wrist X-rays, which reflect the maturity of different types of bones 1

2. Interpretation methods:

   • Greulich-Pyle atlas
   • Tanner-Whitehouse method
   • Automated methods like BoneXpert (which have shown accuracy comparable to manual rating with precision of 0.17-0.18 years) 2

3. Context factors: Bone age may be affected by:

   • Gender
   • Nutritional status
   • Metabolic factors
   • Genetic factors
   • Hormonal status 1

Management Recommendations

For a bone age of -0.9 SD:

1. No specific intervention required

   • This finding is within normal limits
   • Regular growth monitoring is sufficient

2. Follow-up considerations:

   • Routine height and weight measurements at regular pediatric visits
   • No need for additional bone age assessments unless other clinical concerns arise

3. When to consider reassessment:

   • If growth velocity decreases significantly
   • If there are new endocrine symptoms
   • If height percentiles change substantially

When Further Evaluation Is Warranted

Consider additional evaluation only if:

• Bone age falls below -2.0 SD (significant delay)
• Clinical symptoms of endocrine disorders emerge
• Growth velocity decreases significantly
• Height falls below the 3rd percentile 3

Special Considerations

1. Chronic kidney disease: In children with CKD, bone age assessment is recommended to document open epiphyses for assessment of growth potential 3

2. Growth hormone considerations: Persistent growth failure (height below 3rd percentile and height velocity below 25th percentile) beyond 3 months in infants or 6 months in children might warrant further evaluation 3

3. Bone health monitoring: While a bone age of -0.9 SD does not indicate osteopenia or osteoporosis, maintaining good bone health through adequate calcium and vitamin D intake remains important for all children 4

Conclusion

A bone age of -0.9 standard deviations from the mean represents a normal variant in skeletal maturation and does not require specific intervention. Regular monitoring of growth parameters during routine pediatric care is sufficient.