ESPE Abstracts

Background: The BoneXpert method for automated determination of bone age (BA) from hand X-rays was introduced in 2009, covering the Greulich-Pyle BA range up to 17 years for boys and 15 years for girls.

Objective and hypotheses: To present an extension of the BA range of the automated method up to 19 years for boys and 18 years for girls and to validate it against manual rating.

Method: The extension was developed based on images from the First Zurich Longitudinal Study of 231 healthy children born in 1954–56 and followed with annual X-rays of both hands until the age of 20 years. The method was validated on two cross-sectional studies of healthy children from Rotterdam and Los Angeles.

Results: We found a root-mean-square deviation from manual rating of 0.68 and 0.49 years respectively in these two studies for boys in the BA range 17–19 years. For girls in the BA range 15–18 years, the deviations were 0.77 and 0.63 years respectively. Note: For girls in the BA range 17–18 years, the deviations were relatively high, indicating that the Greulich-Pyle BA scale should perhaps stop already at 17 years for girls. Further arguments for this are: 1) Beyond 17 years, ratings become unreliable, putting too much interpretation on the epiphyseal scar, which can persist for years; 2) the end-point of the BA scale is not a distinct event but a fading out; 3) BA beyond 17 years has no clinical importance in physical education or orthopaedics, only in forensics; 4) this would match the end-point at 19 years in boys well, since female bone development is about two years ahead of male development.

Conclusions: With this extension, the automated method performs BA rating as well at the end of puberty, as in the rest of the BA range. The clinical use of BA at the end of puberty includes: 1) the assessment of growth potential, so that GH treatment can be stopped at the optimal time, 2) the assessment of growth potential in pediatric orthopaedics prior to surgical intervention.