{'fraction_non_alphanumeric': 0.017654476670870115, 'fraction_numerical': 0.0037831021437578815, 'mean_word_length': 4.748792270531401, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Site Specificity of Fracture Prediction in Children

We thank Dr Ferrari and colleagues for their interest in our paper. We also apologize for not referring to their excellent paper in our original manuscript; it was only drawn to our attention after this paper was available online. We agree that the data in adults support the concept of site specificity for BMD and fracture risk. However, the data in children are not as supportive even though there is now convincing evidence that BMD is a risk factor for childhood fracture, especially those of the upper limb. Unfortunately, arm or radius BMD was not available from when our study started in 1996. However, we have looked at arm measurements in other samples. In our previous case control study of upper limb fractures, arm BMD was not superior to other sites for total upper limb fractures or wrist and forearm fractures. The only trend to superiority was for wrist and forearm fractures in girls, which would be consistent with the data of Ferrari et al., but for boys with the same fractures, no significant association was present even though the sample size was larger. The most consistent associations in both sexes were for spine and hip bone mineral apparent density (BMAD; which are estimates of true volumetric density). Arm BMD is not as accurate or specific as radial BMD, so this lack of strong association could be caused by measurement issues. However, in a crosssectional study of 415 16-yr-old children, we reported that prevalent upper limb fractures were most strongly associated with total body BMD compared with hip, spine, and radial BMD, which all had weaker but similar fracture discrimination. Other cohorts have not yet reported on arm measures but have reported on associations with total body and spine measures. We purposefully devoted little discussion to total body BMAD because we are in full agreement with Ferrari et al. about this result. This is not a meaningful number because it assumes the total body is a cylinder, and we can only assume there was a significant association because of a correlation with another measure of bone, most likely total body BMD. The hypothesis that Dr Ferrari and colleagues propose is valid and testable. However, at this stage, more data from longitudinal studies are needed to resolve the issue of site specificity for fracture prediction in children.