A new paper by Suma Uday et al reports the use of BoneXpert to study bone age and BHI in deprived Afghan children of age 1.5-2.5 y. This validates version 3 of BoneXpert, which extends the bone age range down to new-borns – the older version of BoneXpert was valid only down to 2.5 years.
Seven percent of the images could not be analysed, because the hand was not placed flat on the film, or because there was an overlapping adult hand – both effects are present in this image of a boy.
To use BoneXpert in toddlers and infants, it is advised to compress the hand flat on detector with a thin plastic plate. The thumb should form an angle of at least 20 degrees to the index finger as shown in this correctly taken X-ray of a boy.
In the study, the Bone Health Index (BHI) was analysed with standard deviation scores, BHI SDS, (aka Z-scores) based on BoneXpert’s reference curves from healthy Parisian boys and girls expressed as a function of bone age. The Afghan children showed an average bone health slightly below normal.
The study recruited 211 Belgian children of Moroccan ethnic origin, and 212 children from the general population.
They were recruited retrospectively from individuals who underwent a radiograph of their left hands to rule out trauma or musculoskeletal abnormalities. Children with pathologies were excluded.
The agreement with a manual (visual) rating is good:
Only 13% of the cases deviated by more than 1 year, which is compatible with a Root Mean Square (RMS) error of 0.66 y. The good agreement was facilitated by a particularly careful manual rater who took into account all the bones and the narrative description of the bone shape features of each age provided in the page annexed to each image of the Greulich Pyle (GP) atlas. The automated analysis was done with BoneXpert version 2 – with version 3 the RMS error is expected to be lower.
The study data are fairly representative of the general populations of these ethnicities, and it is therefore interesting to consider the difference of bone age and age:
The mean difference is compatible with being zero, except perhaps for European Caucasians below the age of seven, who tend to be delayed by 0.3 years.
The GP bone age scales was derived from selected, upper-middle class children in Ohio 1931-42. Since then, many Caucasian populations have been found to be delayed by 0.3-0.7 years relative to the GP scale, so it is interesting that present-day Caucasians seem to have caught up to the GP scale after 80-90 years.
The Bayley-Pinneau method for adult height prediction (AHP) from age, bone age and height was developed in 1952 based on American white children. In 2009, the method was modernised through the BoneXpert AHP based on automated bone age, better math and more recent Caucasian longitudinal studies.
We are proud to present now an extension of the method to cover three major ethnicities in the world: Caucasians, Asians and Africans.
This was possible through access to a longitudinal study of African children in Johannesburg, and a longitudinal study of Asian children in Japan.
The AHP is now based on version 3 of BoneXpert bone age, and for Caucasians it has been extended down to bone age 2 years.
For Caucasians, the difference between version 3 and the old AHP version is less than 1 cm in four out of five cases.