Introduction: Male gender, adolescence and obesity are known risk factors for upper limb fractures, although the mechanism by which obesity confers the increased fracture risk is unknown. In addition, most studies investigating the influence of body fat mass on bone in adolescents have been performed in school based populations using the DXA technique, which does not take into account the material and geometric bone properties.
Methods: We investigated volumetric bone density and cross-sectional bone geometry at the non-dominant forearm using peripheral quantitative computed tomography (pQCT) in 51 obese (BMI z-score >+2) male adolescents (aged 1019 years) at entry of a residential weight loss program in comparison with 51 non-obese age, pubertal stage and height matched controls.
Results: Obese adolescents (OA) had a higher trabecular density (215±33 vs 197±32 mg/cm3; P=0.007) at the distal 4% end, but comparable cortical density (996±60 vs 992±54 mg/cm3; P=0.720) at the proximal 66% site. Trabecular area (158±26 vs 143±33 mm2; P=0.02) as well as cortical area (72±21 vs 65±17 mm2; P=0.08) and periosteal circumference (46.8±4.7 vs 44.8±4.8 mm; P=0.04) were slightly larger in OA. While absolute bone strength index (BSI) assessed at the distal radius (37.1±14.04 vs 31.2±12.27 mg/mm4; P=0.03), was higher in OA, the ratio BSI/ forearm load was lower.
Conclusion: Male OA have greater periosteal circumference, trabecular bone area and density and absolute bone strength at the distal radius. Hence, the higher forearm fracture risk in obese adolescents is not due to a lower bone accumulation, but bone strength is probably not adapted to the excess body weight in case of unusual loading as a fall on outstretched hands.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This work was supported, however, funding details unavailable.
05 - 09 May 2012
European Society of Endocrinology