title: Body composition during childhood and adolescence: relations to bone strength and microstructure.
abstract: BACKGROUND
  Numerous studies have examined the association of body composition with bone development in children and adolescents, but none have used micro-finite element (μFE) analysis of high-resolution peripheral quantitative computed tomography images to assess bone strength.
  
  
  OBJECTIVE
  This study sought to examine the relations of appendicular lean mass (ALM) and total body fat mass (TBFM) to bone strength (failure load) at the distal radius and tibia.
  
  
  METHODS
  This was a cross-sectional study of 198 healthy 8- to <15-year-old boys (n = 109) and girls (n = 89) performed in a Clinical Research Unit.
  
  
  RESULTS
  After adjusting for bone age, height, fracture history, ALM, and TBFM, multiple linear regression analyses in boys and girls, separately, showed robust positive associations between ALM and failure loads at both the distal radius (boys: β = 0.92, P < .001; girls: β = 0.66, P = .001) and tibia (boys: β = 0.96, P < .001; girls: β = 0.66, P < .001). By contrast, in both boys and girls the relationship between TBFM and failure load at the distal radius was virtually nonexistent (boys: β = -0.07; P = .284; girls: β = -0.03; P = .729). At the distal tibia, positive, albeit weak, associations were observed between TBFM and failure load in both boys (β = 0.09, P = .075) and girls (β = 0.17, P = .033).
  
  
  CONCLUSIONS
  Our data highlight the importance of lean mass for optimizing bone strength during growth, and suggest that fat mass may have differential relations to bone strength at weight-bearing vs non-weight-bearing sites in children and adolescents. These observations suggest that the strength of the distal radius does not commensurately increase with excess gains in adiposity during growth, which may result in a mismatch between bone strength and the load experienced by the distal forearm during a fall. These findings may explain, in part, why obese children are over-represented among distal forearm fracture cases.
authors.affiliation: Division of Endocrinology, Department of Medicine (J.N.F., L.K.M., S.K.); Division of Epidemiology, Department of Health Sciences Research (S.A., L.J.M.); Division of Rheumatology, Department of Medicine (S.A.); Department of Physical Medicine and Rehabilitation (N.K.L); and Division of Biomedical Statistics and Informatics, Department of Health Sciences Research (E.J.A., S.J.A.); Mayo Clinic College of Medicine, Rochester, Minnesota, 55905.
authors.forename: Joshua N
authors.initials: JN
authors.lastname: Farr
authors.forename: Shreyasee
authors.initials: S
authors.lastname: Amin
authors.forename: Nathan K
authors.initials: NK
authors.lastname: LeBrasseur
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Atkinson
authors.forename: Sara J
authors.initials: SJ
authors.lastname: Achenbach
authors.forename: Louise K
authors.initials: LK
authors.lastname: McCready
authors.forename: L
authors.initials: L
authors.lastname: Joseph Melton
authors.forename: Sundeep
authors.initials: S
authors.lastname: Khosla
mesh_terms: D000293:Adolescent; D000365:Age Determination by Skeleton; D001823:Body Composition / Q000502:physiology*; D015519:Bone Density; D001846:Bone Development / Q000502:physiology*; D001842:Bone and Bones / Q000502:physiology* / Q000648:ultrastructure*; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D011884:Radius / Q000033:anatomy & histology / Q000502:physiology; D012727:Sex Characteristics; D013977:Tibia / Q000033:anatomy & histology / Q000502:physiology; D014057:Tomography, X-Ray Computed