Summation of ossification ratios of the distal radius, distal ulna, and proximal radius: a novel parameter for pediatric bone age assessment.
Abstract
Background
The Greulich-Pyle atlas is generally used in clinical practice; however, it involves radiation exposure. Our aim was to clarify the correlation between ultrasonic ossification ratios (ORs) and radiographic bone age, and to develop a repeatable ultrasonic parameter for assessing bone age.
Objective
To determine the correlation between ultrasonic ORs and radiographic bone age, and to test the hypothesis that a summed ultrasonic ossification parameter provides a highly correlated, reproducible, radiation‑free method for pediatric bone age assessment.
Materials And Methods
Ultrasonic imaging was performed on seven ossification centers and epiphyses in 144 consecutive patients aged 0.1-18.0 years. The ORs were measured and compared with the radiological bone age. The correlation between ultrasonic ORs and bone age assessed by the Greulich-Pyle atlas was analyzed by the Pearson correlation coefficient. The intra-observer and inter-observer reliability were evaluated using the intraclass correlation coefficient (ICC).
Results
The sum of the ORs of the distal radius, distal ulna, and proximal radius was highly correlated with radiographic bone age (boys: r=0.98; girls: r=0.97). Adding the ORs of other bones did not increase the value of Pearson's r, while summing the ORs of all assessed bones slightly reduced it (boys: r=0.97; girls: r=0.96). The reliability of the sum of the ORs of the radius, ulna, and femur and the sum of the ORs of the distal radius, distal ulna, and proximal radius was identical (intra-observer ICC=0.99 [95% confidence interval (CI) 0.98, 0.99], P<0.001; inter-observer ICC=0.99 [95% CI 0.97, 0.99] for the former and 0.99 [95% CI 0.98, 0.99] for the latter, both P<0.001), which was significantly higher than that of single sonographic parameters.
Conclusion
The sum of the ORs of the distal radius, distal ulna, and proximal radius is an easy-to-operate, efficient, radiation-free, and operator-friendly bone-age indicator with a high correlation to skeletal age and excellent reproducibility. It serves as a practical alternative for pediatric screening and developmental staging.