title: Acetabular version on magnetic resonance imaging: analysis of two different measuring techniques.
abstract: BACKGROUND
  Both increased anteversion and retroversion of the acetabulum can lead to clinical problems. Although computed tomography (CT) is the gold standard in acetabular version imaging, magnetic resonance imaging (MRI) is becoming increasingly popular. We conducted this retrospective study to answer the following questions: 1) can the bony landmarks necessary to outline and measure acetabular version on MRI be consistently and reproducibly identified; 2) are soft-tissue (labral) landmarks comparable to bony landmarks for the measurement of acetabular version?
  
  
  METHODS
  Twenty-nine MRI torsional profile examinations were studied. A total of 232 readings (116 each for right and left sided acetabulae) were involved. Acetabular anteversion angle (AAA) was measured using two different methods (i.e. bony acetabulum landmarks and labrum), by two investigators, at two separate times.
  
  
  RESULTS
  Mean age was 13 years, 8 months with a range of 14 years. There were 12 male patients and 17 female. It was possible to consistently identify bony and labral landmarks in all MR images. AAA measurements using both methods were consistent and reproducible. When comparing the two methods to each other we found them to be in excellent agreement with an ICC of 0.943 (95% confidence interval, 0.927 to 0.956), 37% of all readings were in perfect agreement and 97% were within 5 degrees. The mean difference in measurement between methods was 1.34 degrees.
  
  
  CONCLUSIONS
  Measurement of acetabular version using MRI remains consistent independent of the method used (bone versus labrum). MRI can provide adequate information for calculating acetabular version.
authors.affiliation: Department of Orthopaedics, Rady Children's Hospital, San Diego, CA, USA.
authors.forename: Abd R
authors.initials: AR
authors.lastname: Muhamad
authors.forename: Joana M
authors.initials: JM
authors.lastname: Freitas
authors.forename: James D
authors.initials: JD
authors.lastname: Bomar
authors.forename: Harish
authors.initials: H
authors.lastname: Hosalkar
mesh_terms: D000077:Acetabulum / Q000473:pathology*; D000293:Adolescent; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000706:statistics & numerical data; D008297:Male; D015588:Observer Variation; D012189:Retrospective Studies