Bone Abstracts

Objective: The bone health index (BHI) has previously been shown to be 1.5% lower in Asian children than in Caucasian children, both living in USA. The aim of this study is to present reference curves for BHI of Chinese Han children and to compare to Asian children living in USA.

Method: BHI is derived from the cortical thickness in the three middle metacarpals. It is determined with the BoneXpert medical device, which automatically analyses a standard bone age hand radiograph. The measurement result is independent of the sharpness of the image. The data were from 6200 children from five major cities in China recorded in 2005. For comparison we use the Asian-American reference curves based on 280 children from Los Angeles recorded 1993–2006.

Results: The Chinese reference curves cover the bone age range 3–17 years for boys and 3–15 years for girls and show a steeper rise in puberty for boys than for girls as previously seen in other populations. An average BHI level is defined by the average over the bone age range 7–14 years for boys and 6–14 years for girls. This BHI level is found to be consistent with being the same in Chinese and Asian-American children.

Conclusion: BHI was designed to exhibit the minimum variance for children of the same bone age and gender in a given population. This lead to a scaling of the cortical bone thickens with a certain power of the bone width and the bone length, and this can be understood to ‘take out’ the ‘uninteresting’ dependence on the highly variable size and proportion of the children. The Asian children in USA and China compared in his study could have different adult heights, but were found to have the same BHI. This suggests that BHI could be a good candidate for a universal measure of bone health and that the amount of cortical bone could have reached a similar optimum in these two populations. The broad availability of bone age hand X-rays across the world, as well as over the long history of radiology, makes BHI a useful tool for auxological studies of children’s bone health.

Declaration of interest: H H Thodberg is the owner of Visiana, which holds and markets the BoneXpert medical device for automated determination of bone age. The other authors have nothing to disclose.