title: Staging of hip avascular necrosis: is there a need for DWI?
abstract: BACKGROUND
  No comprehensive study has been performed to stage avascular necrosis of the hip using diffusion-weighted imaging (DWI).
  
  
  OBJECTIVE
  To determine apparent diffusion co-efficient (ADC) alterations in hip avascular necrosis (AVN) and to determine variations of ADC values according to stages of disease.
  
  
  METHODS
  The study is approved by our institutional review board and local ethical committee. Written informed consent was present for each subject. Thirty-five femoral heads of 21 cases affected by AVN were included in the study. Control group consisted of both femoral heads of 10 healthy volunteers. The hips affected by AVN were staged according to Ficat and Arlet classification system from I to IV. All cases underwent to routine hip magnetic resonance imaging (MRI) and DWI performed with a single-shot fast spin echo sequence at a b value of 600 s/mm(2). The ADC values were calculated automatically by placing ROIs on AVN lesions in affected patients and both femoral heads of control group. The median ADC value obtained from femoral heads of control group and that from AVN lesions were compared by Mann-Whitney U test. The median ADC values of AVN lesions at different stages were compared by Kruskal-Wallis test.
  
  
  RESULTS
  The median ADC value of normal bone measured in control group was 185.5 ± 133.2 x 10(-6) mm(2)/s. The median ADC value measured in hip avascular necrosis lesions was 988.0 ± 332.7 x 10(-6) mm(2)/s. ADC values in hip AVN lesions were statistically significantly higher than normal bone marrow (P<0.01). The median ADC values of hips with avascular necrosis at stage I, II, III, IV were 817.5 ± 172.1 x 10(-6) mm(2)/s, 902.0 ± 181.0 x 10(-6) mm(2)/s, 1200.0 ± 363.2 x 10(-6) mm(2)/s and 1024.0 ± 324.0 x 10(-6) mm(2)/s, respectively. There was no statistically significant difference among AVN lesions at stages I, II, III and IV (P>0.05).
  
  
  CONCLUSIONS
  Although DWI is a promising imaging tool that provides valuable diagnostic information in hip AVN, it fails to distinguish between different stages, and therefore is of limited value.
authors.affiliation: Gazi University School of Medicine Department of Radiology, Ankara, Turkey. yusuf@tr.net
authors.forename: A Yusuf
authors.initials: AY
authors.lastname: Öner
authors.forename: Levent
authors.initials: L
authors.lastname: Aggunlu
authors.forename: Sergin
authors.initials: S
authors.lastname: Akpek
authors.forename: Azim
authors.initials: A
authors.lastname: Celik
authors.forename: Patrick
authors.initials: P
authors.lastname: Le Roux
authors.forename: Turgut
authors.initials: T
authors.lastname: Tali
authors.forename: Serap
authors.initials: S
authors.lastname: Gultekin
mesh_terms: D000328:Adult; D000368:Aged; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D005271:Femur Head Necrosis / Q000473:pathology*; D006621:Hip Joint / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D012720:Severity of Illness Index; D055815:Young Adult