title: MRI and the distribution of bone marrow fat in hip osteoarthritis.
abstract: To characterize the distribution of bone marrow fat in hip osteoarthritis (OA) using magnetic resonance imaging (MRI) and to assess its use as a potential biomarker.
  
  
  
  In all, 67 subjects (39 female, 28 male) with either total hip replacement (THA) or different severities of radiographic OA, assessed by Kellgren-Lawrence grading (KLG), underwent 3T MRI of the pelvis using the IDEAL sequence to separate fat and water signals. Six regions of interest (ROIs) were identified within the proximal femur. Within each ROI the fractional-fat distribution, represented by pixel intensities, was described by its mean, standard deviation, skewness, kurtosis, and entropy.
  
  
  
  Hips were graded: 12 as severe symptomatic (THA), 33 had KLG0 or 1, 9 were KLG2, 11 with KLG3, and 2 with KLG4 were analyzed together. The fractional-fat content in the whole proximal femur did not vary with severity in males (mean (SD) 91.2 (6.0)%) but reduced with severity in females from 89.1 (6.7)% (KLG0,1), 91.5 (2.9)% (KLG2), 85.8 (16.7)% (KLG3,4) to 77.5 (11.9)% (THA) (analysis of variance [ANOVA] P = 0.029). These differences were most pronounced in the femoral head, where mean values fell with OA severity in both sexes from 97.9% (2.5%) (KLG0,1) to 73.0% (25.9%) (THA, P < 0.001) with the largest difference at the final stage. The standard deviation and the entropy of the distribution both increased (P < 0.001).
  
  
  
  Descriptors of the fractional fat distribution varied little with the severity of OA until the most severe stage, when changes appeared mainly in the femoral head, and have, therefore, limited value as biomarkers.
  
  
  
  2 J. Magn. Reson. Imaging 2017;45:42-50.
authors.affiliation: Arthritis and Musculoskeletal Medicine, Institute of Medical Sciences, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, UK.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Gregory
authors.affiliation: Arthritis and Musculoskeletal Medicine, Institute of Medical Sciences, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, UK.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Barr
authors.affiliation: Aberdeen Biomedical Imaging Centre, Lillian Sutton Building, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, UK.
authors.forename: Victor
authors.initials: V
authors.lastname: Varela
authors.affiliation: Aberdeen Biomedical Imaging Centre, Lillian Sutton Building, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, UK.
authors.forename: Trevor S
authors.initials: TS
authors.lastname: Ahearn
authors.affiliation: Wyeth Research, Collegeville, Pennsylvania, USA.
authors.forename: Jennifer Lee
authors.initials: JL
authors.lastname: Gardiner
authors.affiliation: Aberdeen Biomedical Imaging Centre, Lillian Sutton Building, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, UK.
authors.forename: Fiona J
authors.initials: FJ
authors.lastname: Gilbert
authors.affiliation: Aberdeen Biomedical Imaging Centre, Lillian Sutton Building, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, UK.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Redpath
authors.affiliation: Arthritis and Musculoskeletal Medicine, Institute of Medical Sciences, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, UK.
authors.forename: James D
authors.initials: JD
authors.lastname: Hutchison
authors.affiliation: Arthritis and Musculoskeletal Medicine, Institute of Medical Sciences, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, UK.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Aspden
mesh_terms: D000273:Adipose Tissue / Q000000981:diagnostic imaging* / Q000473:pathology; D050154:Adiposity; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers; D001853:Bone Marrow / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging* / Q000473:pathology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers
keywords: fractional fat content; hip; imaging biomarker; intramedullary fat; osteoarthritis