title: A novel method to measure femoral component migration by computed tomography: a cadaver study.
abstract: BACKGROUND
  Radiostereometric analysis (RSA) is the most accurate technique to measure implant migration. However, it requires special equipment, technical expertise and analysis software and has not gained wide acceptance. The current paper analyzes a novel method to measure implant migration utilizing widely available computer tomography (CT).
  
  
  METHODS
  Three uncemented total hip replacements were performed in three human cadavers and six tantalum beads were inserted into the femoral bone similar to RSA. Six different 28 mm heads (-3, 0, 2.5, 5.0, 7.5 and 10 mm) were added to simulate five reproducible translations (maximum total point migration) of the center of the head. Implant migration was measured in a 3-D analysis software (Geomagic Studio 7). Repeat manual reconstructions of the center of the head were performed by two investigators to determine repeatability and accuracy.
  
  
  RESULTS
  The accuracy of measurements between the centers of two head sizes was 0.11 mm with a CI 95 % of 0.22 mm. The intra-observer repeatability was 0.13 mm (CI 95 % 0.25 mm). The interrater-reliability was 0.943.
  
  
  CONCLUSIONS
  CT based measurement of head displacement in a cadaver model were highly accurate and reproducible.
authors.affiliation: Hospital for Special Surgery, New York, USA. boettnerf@hss.edu.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Boettner
authors.affiliation: Hospital for Special Surgery, New York, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Sculco
authors.affiliation: Hospital for Special Surgery, New York, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Lipman
authors.affiliation: Hospital for Special Surgery, New York, USA.
authors.forename: Lisa
authors.initials: L
authors.lastname: Renner
authors.affiliation: Hospital for Special Surgery, New York, USA.
authors.forename: Martin
authors.initials: M
authors.lastname: Faschingbauer
mesh_terms: D019644:Arthroplasty, Replacement, Hip; D002102:Cadaver; D005269:Femur / Q000000981:diagnostic imaging*; D005548:Foreign-Body Migration / Q000000981:diagnostic imaging*; D006622:Hip Prosthesis; D006801:Humans; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed
keywords: Cadaver study; Computed tomography; Migration measurement; Total hip arthroplasty