title: MRI analysis for rotation of total knee components.
abstract: OBJECTIVE
  The aim of this study was to analyze rotation of total knee (TKA) implant components using magnetic resonance imaging (MRI) and to assess the reproducibility of results. It was hypothesized that rotation of both femoral and tibial implants would be reliably reproduced.
  
  
  METHODS
  A retrospective analysis of 55 MRI studies in subjects with painful TKA implants was conducted. There were 27 zirconium and 28 cobalt/chrome/molybdenum alloy (CoCrMo) femoral components in the group. The rotation angle of femoral and tibial components was measured and determined. Statistical analysis included tests for reliability, variance between implant groups, standard deviations and confidence intervals.
  
  
  RESULTS
  There was a sufficient inter- and intra-observer reliability determined for rotation in all implants. The inter-observer reliability was notably higher in the zirconium femur group with significant less variance and lower standard deviations than the CoCrMo femoral component comparison group. Standard deviations for femoral rotational analysis were within a clinically acceptable range. The standard deviations were considerably higher in the tibial component rotational analysis.
  
  
  CONCLUSIONS
  MRI analysis of the rotation of femoral implants after TKA allows good reproducibility, especially with review of zirconium implants. There is less reproducibility for tibial components related to the applied geometric method to quantify rotation and not to the MRI technique.
authors.affiliation: Department of Orthopedics and Rheumatology, University Hospital Marburg, Germany. heyse@med.uni-marburg.de
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Heyse
authors.forename: Le Roy
authors.initials: le R
authors.lastname: Chong
authors.forename: Jack
authors.initials: J
authors.lastname: Davis
authors.forename: Friedrich
authors.initials: F
authors.lastname: Boettner
authors.forename: Steven B
authors.initials: SB
authors.lastname: Haas
authors.forename: Hollis G
authors.initials: HG
authors.lastname: Potter
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery; D007720:Knee Prosthesis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D012372:ROC Curve; D016059:Range of Motion, Articular / Q000502:physiology*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012399:Rotation