Bone Age Assessment: Imaging Study and Reporting
A left hand and wrist radiograph (anteroposterior view) is the standard imaging study for bone age assessment, with findings reported using either the Greulich-Pyle atlas or Tanner-Whitehouse 2 (TW2) method 1, 2, 3.
Imaging Technique
The standard approach involves:
- Single AP radiograph of the left hand and wrist - this captures multiple bone types at different maturation stages in one image 1, 2
- High-detail imaging technique with appropriate collimation
- The left side is used by convention for standardization across all methods
Reporting Methods
Primary Assessment Methods
Two validated approaches exist, though they are not interchangeable 4:
Greulich-Pyle Method (Atlas Matching)
- Compare the patient's radiograph to reference standards in the atlas
- Faster but has greater inter-observer variability
- 95% confidence interval for intra-observer variation: -2.46 to 2.18 years 4
Tanner-Whitehouse 2 Method (TW2) - Preferred
- Point-scoring system evaluating individual bones
- More reproducible with less intra-observer variation (95% CI: -1.41 to 1.43 years) 4
- Should be used preferentially, especially for serial measurements 4
Critical Reporting Considerations
The two methods can differ by up to 2.28 years in the same patient 4. Therefore:
- Use only ONE method consistently when following a patient over time 4
- Document which method was used in the report
- Report bone age in years and months
- Include the chronological age for comparison
- Note any significant discrepancies (>2 standard deviations)
Alternative Modalities
While hand/wrist radiography remains standard:
- MRI and ultrasound avoid radiation but require further validation 1, 3
- Automated computer-aided methods (e.g., BoneXpert) reduce variability and assessment time 1, 3
- These alternatives are not yet standard practice but show promise
Age Limitations
- Effective until approximately 18 years - beyond this, hand/wrist maturation is complete 5
- For ages 18-22 years, medial clavicle assessment may be used instead, though this requires different imaging 5
Common Pitfalls
- Avoid mixing methods - the 95% confidence interval for differences between Greulich-Pyle and TW2 is -1.52 to 2.28 years 4
- Ensure adequate image quality with proper positioning
- Consider ethnic and nutritional factors that may affect bone maturation 2, 3
- Sex hormones significantly influence bone age, particularly estrogen for growth plate closure 3