title: Alterations of bone mineral density, bone microarchitecture and strength in patients with ankylosing spondylitis: a cross-sectional study using high-resolution peripheral quantitative computerized tomography and finite element analysis.
abstract: BACKGROUND
  Ankylosing spondylitis (AS) is an inflammatory disease associated with new bone formation and an increased risk of osteoporosis and fractures. The negative effects of AS on bone microarchitecture and strength are unclear. Thus, we conducted an observational study to analyze the effect of AS on bone microarchitecture and strength.
  
  
  METHODS
  Patients with AS (n = 53) and non-AS subjects (n = 85) were recruited for the study. All subjects underwent clinical evaluation, DXA and high-resolution peripheral quantitative CT scans (HRpQCT).
  
  
  RESULTS
  The AS patients were aged 44 ± 12 (mean ± standard deviation) years and had a median disease duration of 17 (interquartile range: 7-27) years. They were found to have lower cortical, trabecular and total vBMD at the distal radius and tibia than non-AS subjects on multivariable regression analysis. Cortical parameters such as cortical thickness and porosity, and bone strength parameters such bone stiffness and stress as estimated by finite element analysis (FEA) in AS patients were significantly worse than that of-non-AS subjects. Among patients with AS, male sex, mSASSS greater than zero and HLA-B27 negative status were associated with worse bone microarchitecture.
  
  
  CONCLUSIONS
  Patients with AS have worse bone mineral density, microarchitecture and strength when compared to non-AS subjects. More research is needed to understand the mechanisms underlying bone pathology in AS and to assess the effect of treatments such as TNF inhibitors on bone quality and fracture risk.
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Canada. nnigilharoon@hsnsudbury.ca.
authors.forename: Nisha
authors.initials: N
authors.lastname: Nigil Haroon
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Canada. eva.szabo@uhn.ca.
authors.forename: Eva
authors.initials: E
authors.lastname: Szabo
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Canada. janet@raboud.net.
authors.forename: Janet M
authors.initials: JM
authors.lastname: Raboud
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Canada. hmcdonald-blumer@mtsinai.on.ca.
authors.forename: Heather
authors.initials: H
authors.lastname: Mcdonald-Blumer
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Canada. Lydia.fung@uhn.ca.
authors.forename: Lydia
authors.initials: L
authors.lastname: Fung
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Canada. josseRG@smh.ca.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Josse
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Canada. Robert.inman@uhn.ca.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Inman
authors.affiliation: Department of Medicine, University of Toronto, Toronto, Canada. angela.cheung@uhn.ca.|Toronto General Hospital, University Health Network, Eaton 7th Floor Rm 7EN221, 200 Elizabeth St., Toronto, ON, M5G 2C4, Canada. angela.cheung@uhn.ca.
authors.forename: Angela M
authors.initials: AM
authors.lastname: Cheung
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D003430:Cross-Sectional Studies; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D013167:Spondylitis, Ankylosing / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000379:methods*