Bone Abstracts

Objective: To assess whether hand-wrist dual-energy x-ray absorptiometry (DXA) can replace radiographs for bone age assessment using the Greulich & Pyle (G&P) and/or Tanner & Whitehouse (TW3) methods.

Methodology: Purposive sampling was used to include a total of 20 patients identified from an Endocrine Clinic; two males and two females from each of 5 age groups (<5; 5 to 7; 8 to 10; 11 to 13; 14 to 16 years). Bone age as determined from DXA and radiographs performed on the same day were compared for each child. Two observers independently assessed all radiographs and DXA scans on two occasions. For each observer, there was a minimum interval of two weeks between the two reads. Adequacy of hand positioning and image quality were assessed using paired t tests. Interclass correlation coefficient and Bland Altman plots were used to evaluate agreement between the observers and correlation between the two imaging modalities.

Findings: The mean chronological age was 9.04 (S.D.±3.8) and 9.8 (S.D.±3.2) years for girls and boys respectively. A significant difference between DXA scans and radiographs (P<0.001) was observed in terms of hand positioning. The ulna was excluded from the scan field in 15% of the left hand DXAs. The overall image quality assessment showed a significant difference (P<0.001) between left hand DXA scans and left hand radiographs. Visibility of soft tissue and fat planes was poor in all DXA scans compared to radiographs. Despite the reduced image quality of DXA, inter-observer agreement for bone age determination was 0.987 for radiographs and 0.980 for DXA using the G&P technique. For Observer 1, intra-observer agreement for radiographs and DXA was 0.993 and 0.983 respectively, and 0.995 and 0.994 respectively for Observer 2. Poor DXA image quality did not allow bone age determination using the TW3 method.

Conclusion: Bone age can be determined from left hand/wrist DXA scans using G&P. However, limited DXA image quality prohibits its use for bone age assessment using the TW3 method.

Acknowledgement: This study was funded by a grant from the Skeletal Dysplasia Group for Teaching & Research.

Disclosure: Dr Amaka Offiah is Convenor of the Skeletal Dysplasia Group for Teaching & Research but consistent with the Society’s Terms of Reference had no input in the grant review process for this study.