title: Comparison of acetabular version angle measurements between prone and reformatted supine computed tomography images.
abstract: OBJECTIVE
  To compare acetabular version angle measurements of CT scans in the prone and reformatted supine positions. CT acetabular version angle measurements have previously been done in the prone position to correct for pelvic tilt. With the advent of multidetector CT, recent studies have evaluated acetabular version angles measured in the supine position. To our knowledge, a comparison between these two approaches has not been performed.
  
  
  METHODS
  Case series in which consecutive CT urography studies of 49 adult patients performed in both prone and supine positions were retrospectively reviewed, and acetabular version angles of both hips measured.
  
  
  METHODS
  Retrospective review of 49 consecutive CT urography studies performed in both prone and supine positions was done, and acetabular version angles of both hips were measured. Two radiologists measured the acetabular version angles independently. Multiplanar reformation of the supine CT images was performed to compensate for pelvic tilt and rotation prior to angle measurements.
  
  
  RESULTS
  There was excellent interobserver agreement between the two readers (ICC = 0.90). Acetabular version angle measurements from the prone CT images were larger compared to reformatted supine images (24.0 and 21.3°, respectively, p < 0.0001), with greater angles found in women. There was strong correlation between supine and prone acetabular version angle measurements with a Pearson correlation coefficient of 0.743.
  
  
  CONCLUSIONS
  Acetabular version angles measured from prone and reformatted supine CT images show strong correlation but are significantly different with larger angles obtained from the former and in women; clinical implications of these findings may require further study in other to determine the best method of version angle measurement. CT acetabular version angle measurement is also reliable with excellent interobserver correlation.
authors: Department of Radiology, Changi General Hospital, 2 Simei Street 3, Singapore, 529889, Singapore, lrchong@gmail.com.
authors: Le Roy
authors: le R
authors: Chong
authors: Chow Wei
authors: CW
authors: Too
mesh_terms: D000077:Acetabulum / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006621:Hip Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D056888:Patient Positioning / Q000379:methods*; D016684:Prone Position; D012016:Reference Values; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012737:Sex Factors; D016683:Supine Position; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014567:Urography; D055815:Young Adult