title: Poor accuracy of plain radiographic measurements of prosthetic migration and alignment in total ankle replacement.
abstract: BACKGROUND
  The rotational position of the leg substantially influences measurements in ankle radiographs after total ankle replacement (TAR). The aim of our study was to further specify the influence of different projections on radiographic parameters used to assess component position after TAR.
  
  
  METHODS
  The effect of varying degrees of internal rotation, flexion, and ab-/adduction on reference lines in anteroposterior and lateral ankle radiographs was investigated in a cadaveric TAR model. Observed variations were then compared with those found in 34 consecutive patients that received a HINTEGRA total ankle prosthesis in our department.
  
  
  RESULTS
  A change of rotation of 20° resulted in a variation of measured reference lines of more than 1.3 cm in anteroposterior radiographs and more than 1 cm in lateral radiographs in our experimental setting. Even higher intraindividual changes of up to 1.4 cm were observed in our in vivo series.
  
  
  CONCLUSIONS
  The findings suggest that rotational position of the leg highly influences measurements in ankle radiographs after TAR. It further raises the question, if previously described radiographic parameters do provide accurate information for the outcome after TAR in clinical routine as suggested in literature.
authors.affiliation: Department of Orthopedics, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria. matthias.braito@tilak.at.
authors.forename: Matthias
authors.initials: M
authors.lastname: Braito
authors.affiliation: Department of Orthopedics, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria. michael.liebensteiner@i-med.ac.at.
authors.forename: Michael
authors.initials: M
authors.lastname: Liebensteiner
authors.affiliation: Department of Orthopedics, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria. dietmar.dammerer@uki.at.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Dammerer
authors.affiliation: Department of Orthopedics, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria. martin.krismer@uki.at.
authors.forename: Martin
authors.initials: M
authors.lastname: Krismer
authors.affiliation: Geometry and CAD Unit, University of Innsbruck, Innrain 52, 6020, Innsbruck, Austria. martin.pfurner@uibk.ac.at.
authors.forename: Martin
authors.initials: M
authors.lastname: Pfurner
authors.affiliation: Department of Orthopedics, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria. rainer.biedermann@i-med.ac.at.
authors.forename: Rainer
authors.initials: R
authors.lastname: Biedermann
mesh_terms: D000843:Ankle Joint / Q000000981:diagnostic imaging*; D058737:Arthroplasty, Replacement, Ankle / Q000009:adverse effects / Q000379:methods*; D006801:Humans; D010003:Osteoarthritis / Q000601:surgery; D011475:Prosthesis Failure; D011859:Radiography; D012189:Retrospective Studies