Reliability and efficiency of three methods of calculating migration percentage on radiographs for hip surveillance in children with cerebral palsy

V. A. Kulkarni, Jon Davids, A. D. Boyles, N. Q. Cung, A. Bagley

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Purpose Hip surveillance programmes for children with cerebral palsy (CP) utilize the migration percentage (MP) measurement to initiate referrals and recommend treatment. This study assesses the reliability and efficiency of three methods of MP measurement on anteroposterior (AP) pelvis radiographs. Methods A total of 20 AP pelvis radiographs (40 hips) of children with CP were measured by three raters on two occasions using three methods: digital measurement (DM) on a Picture Archiving and Communication System monitor, computer-aided measurement (CA) using a digital templating tool and mobile device application measurement (MA) using a freely available MP measurement tool. For each method, the time required to complete the MP measurement of both hips on each AP pelvis radiograph was measured. Intra-class correlation coefficient (ICC) was used to determine reliability, and analysis of variance was used to compare groups. Results All three methods of determining MP showed excellent inter-rater and intra-rater reliability (ICC 0.976 to 0.989). The mean absolute difference in MP measurement was not significant between trials for a single rater (DM 2.8%, CA 1.9%, MA 2.2%) or between raters (DM 3.6%, CA 2.9%, MA 3.6%). The mean time to complete MP measurement was significantly different between methods, with DM = 151 seconds, CA = 73 seconds and MA = 80 seconds. Conclusion All three MP measurement methods were highly reliable with clinically acceptable measurement error. The 1 Department of Orthopaedic Surgery, Shriners Hospitals for Children – Northern California, Sacramento, California, USA 2 Department of Orthopaedic Surgery, Children’s Hospital Colorado, Colorado Springs, Colorado, USA Correspondence should be sent to V. A. Kulkarni, Shriners Hospitals for Children – Northern California, 2425 Stockton Boulevard, Sacramento, CA 95817, USA. E-mail: time required to measure a hip surveillance radiograph can be reduced by approximately 50% by utilizing a computer-based or mobile application-based MP measurement tool. Level of Evidence III.

Original languageEnglish (US)
Pages (from-to)145-151
Number of pages7
JournalJournal of Children's Orthopaedics
Issue number2
StatePublished - Apr 1 2018
Externally publishedYes


  • Cerebral palsy
  • Hip displacement
  • HipScreen application
  • Migration percentage
  • Reliability

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health
  • Orthopedics and Sports Medicine


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