title: Assessment of prosthesis alignment after revision total knee arthroplasty using EOS 2D and 3D imaging: a reliability study.
abstract: BACKGROUND
  A new low-dose X-ray device, called EOS, has been introduced for determining lower-limb alignment in 2D and 3D. Reliability has not yet been assessed when using EOS on lower limbs containing a knee prosthesis. Therefore purpose of this study was to determine intraobserver and interobserver reliability of EOS 2D and 3D knee prosthesis alignment measurements after revision total knee arthroplasty (rTKA).
  
  
  METHODS
  Forty anteroposterior and lateral images of 37 rTKA patients were included. Two observers independently performed measurements on these images twice. Varus/valgus angles were measured in 2D (VV2D) and 3D (VV3D). Intraclass correlation coefficients and the Bland and Altman method were used to determine reliability. T-tests were used to test potential differences.
  
  
  RESULTS
  Intraobserver and interobserver reliability were excellent for VV2D and VV3D. No significant difference or bias between the first and second measurements or the two observers was found. A significant mean and absolute difference of respectively 1.00° and 1.61° existed between 2D and 3D measurements.
  
  
  CONCLUSIONS
  EOS provides reliable varus/valgus measurements in 2D and 3D for the alignment of the knee joint with a knee prosthesis. However, significant differences exist between varus/valgus measurements in 2D and 3D.
authors.affiliation: Department of Orthopaedics, University of Groningen, University Medical Center Groningen, Gronigen, The Netherlands.
authors.forename: Marrigje F
authors.initials: MF
authors.lastname: Meijer
authors.affiliation: Department of Orthopaedics, University of Groningen, University Medical Center Groningen, Gronigen, The Netherlands.
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Boerboom
authors.affiliation: Department of Orthopaedics, University of Groningen, University Medical Center Groningen, Gronigen, The Netherlands.
authors.forename: Martin
authors.initials: M
authors.lastname: Stevens
authors.affiliation: Department of Orthopaedics, University of Groningen, University Medical Center Groningen, Gronigen, The Netherlands.
authors.forename: Sjoerd K
authors.initials: SK
authors.lastname: Bulstra
authors.affiliation: Department of Trauma Surgery, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Inge H F
authors.initials: IH
authors.lastname: Reininga
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation* / Q000379:methods; D007719:Knee Joint / Q000000981:diagnostic imaging*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D055815:Young Adult