title: Dual energy X-ray absorptiometry of the knee in spinal cord injury: methodology and correlation with quantitative computed tomography.
abstract: METHODS
  Comparison of diagnostic tests; methodological validation.
  
  
  OBJECTIVE
  Primary: to investigate the precision and reliability of a knee bone mineral density (BMD) assessment protocol that uses an existing dual energy X-ray absorptiometry (DXA) forearm acquisition algorithm in individuals with spinal cord injury (SCI). Secondary: to correlate DXA-based knee areal BMD with volumetric BMD assessments derived from quantitative computed tomography (QCT).
  
  
  METHODS
  Academic medical center, Chicago, IL, USA.
  
  
  METHODS
  
  
  
  METHODS
  a convenience sample of 12 individuals with acute SCI recruited for an observational study of bone loss and 34 individuals with chronic SCI who were screened for a longitudinal study evaluating interventions to increase BMD.
  
  
  METHODS
  Root-mean-square standard deviation (RMS-SD) and intra/inter-rater reliability of areal BMD acquired at three knee regions using an existing DXA forearm acquisition algorithm; correlation of DXA-based areal BMD with QCT-derived volumetric BMD.
  
  
  RESULTS
  The RMS-SD of areal BMD at the distal femoral epiphysis, distal femoral metaphysis and proximal tibial epiphysis averaged 0.021, 0.012 and 0.016 g cm(-2), respectively, in acute SCI and 0.018, 0.02 and 0.016 g cm(-2) in chronic SCI. All estimates of intra/inter-rater reliability exceeded 97% and DXA-based areal BMD was significantly correlated with QCT-derived volumetric BMD at all knee regions analyzed.
  
  
  CONCLUSIONS
  Existing DXA forearm acquisition algorithms are sufficiently precise and reliable for short-term assessments of knee BMD in individuals with SCI. Future work is necessary to quantify the reliability of this approach in longitudinal investigations and to determine its ability to predict fractures and recovery potential.
  
  
  BACKGROUND
  This work was funded by the Department of Defense, grant number DOD W81XWH-10-1-0951, with partial support from Merck & Co, Inc.
authors.affiliation: Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
authors.forename: J G
authors.initials: JG
authors.lastname: McPherson
authors.affiliation: Department of Kinesiology, University of Calgary, Calgary, AB, Canada.
authors.forename: W B
authors.initials: WB
authors.lastname: Edwards
authors.affiliation: Department of Medicine, Lincoln Medical Center, Weill Cornell Medical College, New York, NY, USA.
authors.forename: A
authors.initials: A
authors.lastname: Prasad
authors.affiliation: Department of Biomedical Engineering, Worcester Polytechnic Institute, Worcester, MA, USA.
authors.forename: K L
authors.initials: KL
authors.lastname: Troy
authors.affiliation: Department of Medical Social Sciences, Northwestern University, Chicago, IL, USA.
authors.forename: J W
authors.initials: JW
authors.lastname: Griffith
authors.affiliation: Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Schnitzer
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D001847:Bone Diseases / Q000175:diagnosis / Q000209:etiology*; D015331:Cohort Studies; D005260:Female; D005542:Forearm / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D007717:Knee / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013119:Spinal Cord Injuries / Q000150:complications* / Q000473:pathology*; D015898:Tomography Scanners, X-Ray Computed; D055815:Young Adult