title: Pelvic bone asymmetry in 323 study participants receiving abdominal CT scans.
abstract: METHODS
  Retrospective review of all CT scans of pelvis and abdomen performed at our institution in October and November 2000.
  
  
  OBJECTIVE
  To determine the prevalence and extent of radiographic pelvic asymmetry in a population of patients not preselected for having low back pain.
  
  
  BACKGROUND
  Pelvic asymmetry refers to asymmetric positioning of landmarks on the two sides of the pelvis and may have a structural or functional etiology. Pelvic asymmetry can be associated with the presence of true leg length discrepancy, lead to false diagnosis or inaccurate measurement of leg length discrepancy, or itself be independently associated with back pain. Although the prevalence of pelvic asymmetry has been reported in patients with back pain to be 24-91%, its prevalence in the general population is not known.
  
  
  METHODS
  A total of 323 consecutive CT scans of the pelvis/abdomen were assessed for pelvic asymmetry by one of three examiners. Pelvic asymmetry was defined as an unequal distance from the iliac crests to the acetabuli bilaterally, measured on the anteroposterior scout view of the CT scan. Measurements made on 30 randomly selected scans by the three examiners were used to assess interrater reliability of the measurement method.
  
  
  RESULTS
  Pelvic asymmetry ranged in magnitude from -11 mm to 7 mm [right pelvis (mm) - left pelvis (mm)]. Pelvic asymmetry was >5 mm in 17 of 323 (5.3%) and >10 mm in 2 of 323 (0.6%) of the subjects; 172 of 323 (53.3%) had a smaller right hemipelvis (mean asymmetry = -3.0 mm). A total of 95 of 323 (29.4%) had a smaller left hemipelvis (mean asymmetry = 2.1 mm). The intraclass correlation coefficient [ICC(2,1)] between the three observers was high (0.91).
  
  
  CONCLUSIONS
  Pelvic asymmetry of >5 mm was uncommon, with a prevalence of approximately 5% in the population studied. CT scanography was found to be a practical and reliable method for the assessment of suspected pelvic asymmetry.
authors.affiliation: Division of Rheumatology, Faculty of Medicine, Department of Health Care and Epidemiology, Vancouver General Hospital, British Columbia, Canada. mbadii@arthritisresearch.ca
authors.forename: Maziar
authors.initials: M
authors.lastname: Badii
authors.forename: Sonya
authors.initials: S
authors.lastname: Shin
authors.forename: William C
authors.initials: WC
authors.lastname: Torreggiani
authors.forename: Bojana
authors.initials: B
authors.lastname: Jankovic
authors.forename: Paul
authors.initials: P
authors.lastname: Gustafson
authors.forename: Peter L
authors.initials: PL
authors.lastname: Munk
authors.forename: John M
authors.initials: JM
authors.lastname: Esdaile
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007870:Leg Length Inequality / Q000000981:diagnostic imaging / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010384:Pelvic Bones / Q000002:abnormalities* / Q000000981:diagnostic imaging*; D011860:Radiography, Abdominal; D012189:Retrospective Studies; D012446:Sacroiliac Joint / Q000002:abnormalities; D014057:Tomography, X-Ray Computed