title: How Critical is Patient Positioning in Radiographic Assessment of the Hip in Cerebral Palsy When Measuring Migration Percentage?
abstract: BACKGROUND
  Migration percentage (MP) is an accepted method of assessing lateral displacement of the femoral head in children with cerebral palsy (CP). Difficulty in positioning of patients for pelvic radiography remains a concern for the reliability of the MP.
  
  
  METHODS
  This 2-part quantitative study examined 100 anteroposterior pelvic radiographs for children with CP. Fifty were from a region that had a positioning protocol for hip surveillance of children with CP and 50 images were from a region without. Images were assessed for acceptability of position in relation to hip abduction/adduction and/or pelvic rotation.Ten images deemed Acceptable or Borderline from the region with no protocol were then randomly selected. MP was measured on 2 separate occasions by 5 children's orthopaedic surgeons and statistically analyzed for intrarater and interrater reliability.
  
  
  RESULTS
  There was no statistically significant difference in the acceptability of images between the 2 regions with 60% to 66% of the images meeting the criteria outright. When allowances were made for slight variation of abduction/adduction within 5 degrees, 74% to 80% of the images were acceptable.Reliability was variable with limits of agreement between 4.96% and 15.15%. Observers more familiar with the software measuring package had higher reliability within and between occasions. Variability within and between observers decreased as MP increased.
  
  
  CONCLUSIONS
  Poor positioning did not appear to be the main reason for the variation in reliability of MP. Repeat measurements were reliable although standardized technique, training, and familiarity with software measuring programmes did influence outcomes.
authors.affiliation: *NHS Fife, Victoria Hospital, Kirkcaldy †Ninewells Hospital and Medical School, Dundee ‡Perth Royal Infirmary, Perth §Royal Hospital for Sick Children, Glasgow ∥Royal Aberdeen Children's Hospital, Aberdeen ¶School of Medicine, University of St Andrews, St Andrews #Royal Hospital for Sick Children, Edinburgh, Scotland.
authors.forename: Katie
authors.initials: K
authors.lastname: Kinch
authors.forename: Donald M
authors.initials: DM
authors.lastname: Campbell
authors.forename: James G B
authors.initials: JG
authors.lastname: Maclean
authors.forename: Heather S
authors.initials: HS
authors.lastname: Read
authors.forename: Simon L
authors.initials: SL
authors.lastname: Barker
authors.forename: James E
authors.initials: JE
authors.lastname: Robb
authors.forename: Mark S
authors.initials: MS
authors.lastname: Gaston
mesh_terms: D000293:Adolescent; D002547:Cerebral Palsy / Q000150:complications / Q000000981:diagnostic imaging*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006617:Hip Dislocation / Q000000981:diagnostic imaging* / Q000209:etiology; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D056888:Patient Positioning; D011859:Radiography; D015203:Reproducibility of Results