title: Femoral neck cortical geometry measured with magnetic resonance imaging is associated with proximal femur strength.
abstract: BACKGROUND
  Magnetic resonance imaging (MRI) is a promising medical imaging technique that we used to assess femoral neck cortical geometry.
  
  
  OBJECTIVE
  Our primary objective was to assess whether cortical bone in the femoral neck assessed by MRI was associated with failure load in a simulated sideways fall, with and without adjustment for total bone size. Our secondary objective was to assess the reliability of the MRI measurements.
  
  
  METHODS
  We imaged 34 human cadaveric proximal femora using MRI and dual-energy X-ray absorptiometry (DXA). MRI measurements of cross-sectional geometry at the femoral neck were the cortical cross-sectional area (CoCSA(MRI)), second area moment of inertia (x axis; Ix(MRI)), and section modulus (x axis; Zx(MRI)). DXA images were analyzed with the standard Hologic protocol. From DXA, we report the areal bone mineral density (aBMD(DXA)) in the femoral neck and trochanteric subregions of interest. The femora were loaded to failure at 100 mm/s in a sideways fall configuration (15 degrees internal rotation, 10 degrees adduction).
  
  
  RESULTS
  Failure load (N) was the primary outcome. We observed that the femoral neck CoCSA(MRI) and Ix(MRI) were strongly associated with failure load (r (2)=0.46 and 0.48, respectively). These associations were similar to those between femoral neck aBMD and failure load (r (2)=0.40), but lower than the associations between trochanteric aBMD and failure load (r (2)=0.70).
  
  
  CONCLUSIONS
  We report that MRI holds considerable promise for measuring cortical bone geometry in the femoral neck and for predicting strength at the proximal femur.
authors.affiliation: Department of Orthopaedics, University of British Columbia, 828 West 10th Avenue, Vancouver, BC, V5Z 1L8, Canada.
authors.forename: S L
authors.initials: SL
authors.lastname: Manske
authors.forename: T
authors.initials: T
authors.lastname: Liu-Ambrose
authors.forename: P M
authors.initials: PM
authors.lastname: de Bakker
authors.forename: D
authors.initials: D
authors.lastname: Liu
authors.forename: S
authors.initials: S
authors.lastname: Kontulainen
authors.forename: P
authors.initials: P
authors.lastname: Guy
authors.forename: T R
authors.initials: TR
authors.lastname: Oxland
authors.forename: H A
authors.initials: HA
authors.lastname: McKay
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D005260:Female; D005264:Femoral Fractures / Q000473:pathology* / Q000503:physiopathology; D005269:Femur / Q000503:physiopathology; D005272:Femur Neck / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013314:Stress, Mechanical