title: Central QCT reveals lower volumetric BMD and stiffness in premenopausal women with idiopathic osteoporosis, regardless of fracture history.
abstract: BACKGROUND
  Idiopathic osteoporosis (IOP) affects otherwise healthy young individuals with intact gonadal function and no secondary cause of bone fragility. In premenopausal women with IOP, a low trauma fracture is evidence of impaired bone quality and strength. The extent to which low bone mineral density (BMD) by dual-energy x-ray absorptiometry (DXA) reflects low volumetric BMD, bone microstructure, and strength is uncertain in the absence of low trauma fracture.
  
  
  OBJECTIVE
  The objective of the study was to compare three-dimensional volumetric BMD and bone stiffness in premenopausal women with IOP based on fracture history, those with idiopathic low BMD (Z score ≤ -2.0) and no low trauma fracture, and normal age-matched controls.
  
  
  METHODS
  We measured volumetric BMD and bone geometry by central quantitative computed tomography (cQCT) scans of the spine and hip and estimated bone stiffness by finite element analysis of cQCT data sets in 32 premenopausal women with IOP, 12 with idiopathic low BMD, and 34 controls.
  
  
  RESULTS
  Subjects had comparable decreases in total and trabecular volumetric BMD, cortical thickness, and whole-bone stiffness compared with controls, regardless of fracture history. These differences remained significant after controlling for age, body mass index, and bone size. The positive predictive values of a DXA Z score of -2.0 or less for a cQCT volumetric BMD Z score of -2.0 or less were 95% at the lumbar spine, 90% at the total hip, and 86% at the femoral neck.
  
  
  CONCLUSIONS
  Women with idiopathic low BMD alone and those with low trauma fractures had comparable deficits in bone mass, structure, and stiffness. Low areal BMD by DXA is fairly accurate for predicting low volumetric BMD by cQCT. These results are consistent with three-dimensional bone imaging at the iliac crest, radius, and tibia in premenopausal IOP and suggest that the term osteoporosis may be appropriate in women with Z scores below -2.0, whether or not there is a history of fracture.
authors.affiliation: Department of Medicine, PH8-864, Columbia University, College of Physicians and Surgeons, 630 West 168th Street, New York, New York 10032, USA. ac1044@columbia.edu
authors.forename: Adi
authors.initials: A
authors.lastname: Cohen
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Lang
authors.forename: Donald J
authors.initials: DJ
authors.lastname: McMahon
authors.forename: X Sherry
authors.initials: XS
authors.lastname: Liu
authors.forename: X Edward
authors.initials: XE
authors.lastname: Guo
authors.forename: Chiyuan
authors.initials: C
authors.lastname: Zhang
authors.forename: Emily M
authors.initials: EM
authors.lastname: Stein
authors.forename: David W
authors.initials: DW
authors.lastname: Dempster
authors.forename: Polly
authors.initials: P
authors.lastname: Young
authors.forename: Isra
authors.initials: I
authors.lastname: Saeed
authors.forename: Joan M
authors.initials: JM
authors.lastname: Lappe
authors.forename: Robert R
authors.initials: RR
authors.lastname: Recker
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Shane
mesh_terms: D000293:Adolescent; D000328:Adult; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005260:Female; D020342:Finite Element Analysis; D050723:Fractures, Bone / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D008875:Middle Aged; D010024:Osteoporosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D017697:Premenopause / Q000502:physiology*; D011859:Radiography