title: Dual energy x-ray absorptiometry analysis contributes to the prediction of hip osteoarthritis progression.
abstract: BACKGROUND
  To determine if structural bone parameters obtained from dual energy X-ray absorptiometry (DXA) contribute to the prediction of progression of hip osteoarthritis (OA) and to test if the difference between the most affected (OA) hip and the contralateral hip adds to this prediction.
  
  
  METHODS
  The study group involves a prospective cohort of 189 patients that met the American College of Rheumatology (ARC) classification criteria for hip osteoarthritis. Progression was defined as 20% joint space narrowing or total hip replacement within a two years follow up. Software was developed to calculate geometrical aspects and bone mineral density (BMD) in different regions of interest of the proximal femur. Logistic regression was used to test if Kellgren and Lawrence (K-L) scores and DXA parameters can predict progression of OA. Models were compared using -2log likelihood tests, R2 Nagelkerke and areas under the Receiver Operator Characteristic curves, assessed using 10-fold cross validation.
  
  
  RESULTS
  The model that included the DXA variables was significantly better in predicting hip OA progression than the model with K-L score of the affected side alone (P < 0.01). The addition of the differences in DXA parameters between the most affected and contralateral hip in the superior part of the femoral head, trochanteric and intertrochanteric area further improved the prediction of progression (P < 0.05). K-L score of the affected side was still the most significant single variable in the models.
  
  
  CONCLUSIONS
  DXA parameters can significantly contribute to the prediction of progression in patients with hip osteoarthritis. The analysis of the DXA differences between the hips of the patient represents a small but significant contribution to this prediction. These analyses show the importance of bone density changes in the etiology of OA.
authors.affiliation: Orthopaedic Research Laboratory, Erasmus Medical Center, Dr Mollewaterplein 50, 3000 CA, Rotterdam, The Netherlands. m.castanobetanocurt@erasmusmc.nl
authors.forename: Martha C Castaño
authors.initials: MC
authors.lastname: Betancourt
authors.forename: Jacqueline C Van der
authors.initials: JC
authors.lastname: Linden
authors.forename: Fernando
authors.initials: F
authors.lastname: Rivadeneira
authors.forename: Rianne M
authors.initials: RM
authors.lastname: Rozendaal
authors.forename: Sita M Bierma
authors.initials: SM
authors.lastname: Zeinstra
authors.forename: Harrie
authors.initials: H
authors.lastname: Weinans
authors.forename: Jan H
authors.initials: JH
authors.lastname: Waarsing
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D019540:Area Under Curve; D015519:Bone Density; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D012372:ROC Curve