title: Pelvic orientation and assessment of hip dysplasia in adults.
abstract: BACKGROUND
  The study was performed to qualify the source material of 4151 pelvic radiographs for the research into the relationship between unrecognised childhood hip disorders and the development of hip osteoarthrosis, and to investigate the effect of varying degrees of pelvic tilt and rotation on the measurements of radiographic indices of hip dysplasia.
  
  
  METHODS
  We investigated the effect of varying pelvic orientation on radiographic measurements of acetabular dysplasia using a cadaver model. Results from the cadaver study were used to validate the radiographic assessments of acetabular dysplasia in the longitudinal survey cohort of the Copenhagen City Heart Study (CCHS; Osteoarthrosis Sub-study). 1) Cadaver pelvises and proximal femurs from a male and a female donor were mounted anatomically in holding devices allowing independent inclination/reclination and rotation. An AP pelvic radiograph was recorded at each 3 degrees increment. The most widely used radiographic parameters of hip dysplasia were assessed. 2) Critical limits of acceptable rotation and inclination/reclination of pelvises were determined on 4151 standing, standardised pelvic radiographs of the CCHS cohort.
  
  
  RESULTS
  Wiberg's CE angle, Sharp's angle, the x-coordinate of Goodman's Cartesian coordinate system, and the acetabular depth ratio were significantly affected by varying rotation and inclination/reclination of the cadaver pelvises. Femoral head extrusion index was not significantly affected within the applied rotation and inclination/reclination of the cadaver study. Application of the corresponding critical limits of Tönnis' foramen obturator index of 0.7-1.8 meant that 188 of 4151 (4.5%) of the CCHS-III pelvic radiographs had to be omitted from further studies.
  
  
  CONCLUSIONS
  To ensure a neutral starting point and reproducible readings, especially in epidemiological and clinical studies, and when performing preoperative planning and follow-up of patients undergoing redirectional pelvic osteotomies, it is important that all aspects of the radiographic examination are controlled and reproducible. Furthermore, we found that studies of acetabular dysplasia based on supine urograms or colon radiographs without information about pelvic orientation, centering of the X-ray beam and tube to film distance, run a serious risk of erroneous measurements.
authors.affiliation: Departments of Orthopaedic Surgery, Copenhagen University Hospital, Rigshospitalet, Denmark. sjac@dadlnet.dk
authors.forename: Steffen
authors.initials: S
authors.lastname: Jacobsen
authors.forename: Stig
authors.initials: S
authors.lastname: Sonne-Holm
authors.forename: Bjarne
authors.initials: B
authors.lastname: Lund
authors.forename: Kjeld
authors.initials: K
authors.lastname: Søballe
authors.forename: Thomas
authors.initials: T
authors.lastname: Kiaer
authors.forename: Hans
authors.initials: H
authors.lastname: Rovsing
authors.forename: Henrik
authors.initials: H
authors.lastname: Monrad
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging; D000328:Adult; D000368:Aged; D002102:Cadaver; D015331:Cohort Studies; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging; D006617:Hip Dislocation / Q000150:complications / Q000000981:diagnostic imaging*; D006618:Hip Dislocation, Congenital / Q000150:complications / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging* / Q000209:etiology; D010388:Pelvis / Q000000981:diagnostic imaging*; D011859:Radiography