title: Peripheral quantitative computed tomography-derived muscle density and peripheral magnetic resonance imaging-derived muscle adiposity: precision and associations with fragility fractures in women.
abstract: OBJECTIVE
  To determine the degree to which muscle density and fractures are explained by inter and intramuscular fat (IMF).
  
  
  METHODS
  Women ⋝50 years of age (Hamilton, ON, Canada) had peripheral magnetic resonance imaging and peripheral quantitative computed tomography scans at 66% of the tibial length. Muscle on computed tomography images was segmented from subcutaneous fat and bone using fixed thresholds, computing muscle density. IMF was segmented from muscle within magnetic resonance images using a region-growing algorithm, computing IMF volume. Fracture history over the last 14 years was obtained. Odds ratios for fractures were determined for muscle density, adjusting for IMF volume, total hip BMD, age and body mass index.
  
  
  RESULTS
  Women with a history of fractures were older (N=32, age:75.6±8.3 years) than those without (N=39, age: 67.0±5.2 years) (<0.01). IMF volume explained 49.3% of variance in muscle density (p<0.001). Odds for fractures were associated with lower muscle density even after adjusting for IMF volume but were attenuated after adjusting for age.
  
  
  CONCLUSIONS
  Muscle adiposity represents only 50% of the muscle density measurement. Properties of muscle beyond its adiposity may be related to fractures, but larger and prospective studies are needed to confirm these associations.
authors.affiliation: Osteoporosis Program, University Health Network, Toronto, ON, Canada.
authors.forename: A K O
authors.initials: AK
authors.lastname: Wong
authors.forename: K A
authors.initials: KA
authors.lastname: Beattie
authors.forename: K K H
authors.initials: KK
authors.lastname: Min
authors.forename: C
authors.initials: C
authors.lastname: Gordon
authors.forename: L
authors.initials: L
authors.lastname: Pickard
authors.forename: A
authors.initials: A
authors.lastname: Papaioannou
authors.forename: J D
authors.initials: JD
authors.lastname: Adachi
mesh_terms: D050154:Adiposity; D000368:Aged; D000465:Algorithms; D019540:Area Under Curve; D005260:Female; D050723:Fractures, Bone; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D009132:Muscles / Q000033:anatomy & histology; D016017:Odds Ratio; D012372:ROC Curve; D014057:Tomography, X-Ray Computed / Q000379:methods*