Do Bone Mineral Density, Bone Geometry and the Functional Muscle-Bone Unit Explain Bone Fractures in Healthy Children and Adolescents?

Background/Aims: Because the increasing fracture incidence has not been understood, the present study compares variables of the muscle-bone interaction to examine the hypothesis that an impaired adaptation of bone strength to muscle forces explains this phenomenon. Methods: The forearm of 220 individuals (mean age 11.1 +/- 3.2 years; range 5.5-17.4 years) was analyzed by peripheral quantitative computed tomography. Bone mineral content (BMC), bone mineral density, periosteal circumference, cortical area, strength strain index (SSI) and muscle area (MA) were measured at the distal and proximal radius of the non-dominant forearm. Maximum isometric grip force was measured by a dynamometer. The fracture history was evaluated by a questionnaire after a period of 5 +/- 1.7 years. Results: During the observational period at least one fracture appeared in 78 children and adolescents (35.5%). Individuals with and without fractures were not different in age, height, weight, and body mass index. Variables of bone mineral density, bone geometry and muscle force were not different between both groups. BMC, MA and SSI were dependent on age and sex. Conclusion: Fracture risk in healthy children and adolescents is not sufficiently explained by volumetric bone mineral density, the skeletal phenotype and indices of the functional muscle-bone unit. Copyright (C) 2010 S. Karger AG, Basel