title: High and low density in the same bone: a study on children and adolescents with mild osteogenesis imperfecta.
abstract: Children and adolescents with osteogenesis imperfecta (OI) generally have low bone mineral density (BMD) at the lumbar spine and hip. However, the effects of the disease on diaphyseal bone have not been well characterized, even though long-bone fractures are common in such patients. In this study on 42 fully mobile children and adolescents with mild OI (age 6-19 years; 17 girls), lumbar spine, radius (metaphysis and diaphysis) and second metacarpal (diaphysis) were analyzed using dual-energy X-ray absorptiometry, peripheral quantitative computed tomography and radiogrammetry, respectively. Bone mineral content at the lumbar spine, radial metaphysis and radial diaphysis was between 25% and 31% lower than in age-matched healthy children and adolescents. At the lumbar spine and radial metaphysis, bone size (as estimated from projection area and cross-sectional area, respectively) was normal or only slightly below the results expected for healthy individuals, whereas bone size was very small at the diaphyseal sites of the radius and the second metacarpal. Total volumetric BMD is defined as the ratio between bone mineral content and bone volume. Therefore, these differences in bone size between skeletal locations led to markedly discrepant results for total volumetric BMD. Total volumetric BMD was low at the lumbar spine (23% below result expected for healthy subjects of the same age) and the radial metaphysis (-15%) but elevated at the radial diaphysis (+25%; all differences to controls significant at P < 0.001). Despite high volumetric BMD, estimated bending strength at the radial diaphysis was very low. These results demonstrate that volumetric BMD can be abnormally high and low within the same bone in the same individual and highlight the fact that volumetric BMD at diaphyseal sites does not provide a good estimate of bone strength when bone size is abnormal.
authors.affiliation: Genetics Unit, Shriners Hospital for Children, 1529 Cedar Avenue, Montreal, Canada QC H3G 1A6. frauch@shriners.mcgill.ca
authors.forename: Frank
authors.initials: F
authors.lastname: Rauch
authors.forename: Christof
authors.initials: C
authors.lastname: Land
authors.forename: Sylvie
authors.initials: S
authors.lastname: Cornibert
authors.forename: Eckhard
authors.initials: E
authors.lastname: Schoenau
authors.forename: Francis H
authors.initials: FH
authors.lastname: Glorieux
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D000886:Anthropometry; D015519:Bone Density / Q000502:physiology*; D002648:Child; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D050279:Metacarpal Bones / Q000473:pathology / Q000503:physiopathology*; D010013:Osteogenesis Imperfecta / Q000473:pathology / Q000503:physiopathology*; D011884:Radius / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed