title: [Should we use hip-ankle radiographs to assess the coronal alignment after total knee arthroplasty?].
abstract: BACKGROUND
  There is no consensus on whether hip-ankle radiographs or rather standardized a‑p knee-radiographs should be used to assess implant position and coronal alignment after total knee arthroplasty (TKA). This study investigates whether implant position and alignment after TKA can reproducibly be assessed using a‑p knee-radiographs rather than hip-ankle radiographs.
  
  
  METHODS
  This study was performed on 100 weight-bearing hip-ankle radiographs after conventional primary TKA. The true mechanical and anatomical femorotibial angle as well as coronal implant position was assessed on hip-ankle radiographs. The radiographs were then cropped to 80, 60 and 40 % of the leg-length and tibial coronal implant position, and the anatomical axis and a surrogate mechanical axis were obtained. The difference in the alignment parameters between the hip-ankle radiographs were statistically compared with the cropped radiographs and the inter-observer correlation coefficient (ICC) was calculated.
  
  
  RESULTS
  The ICC for measurement of the mechanical femorotibial angle was higher in hip-ankle radiographs (0.95) when compared with a radiograph cropped to 40 % (0.61). There was a significant difference in the mechanical femorotibial angle between hip-ankle radiographs and any cropped radiograph. However, there were no significant differences in coronal implant position and the anatomical femorotibial angle between hip-ankle radiographs and any cropped radiograph.
  
  
  CONCLUSIONS
  We conclude that standard a‑p knee-radiographs are insufficient to assess the mechanical alignment following TKA. However, standard a‑p knee-radiographs are appropriate to assess the implant position when referenced against the anatomical axes. Weight-bearing hip-ankle radiographs should be questioned as a routine after TKA.
authors.affiliation: Klinik und Poliklinik für Orthopädie und Unfallchirurgie, Uniklinik Köln, Joseph-Stelzmann-Straße 9, 50931, Köln, Deutschland. jens.dargel@uk-koeln.de.|Cologne Center for Musculoskeletal Biomechanics, Medizinische Fakultät, Universität Köln, Köln, Deutschland. jens.dargel@uk-koeln.de.
authors.forename: J
authors.initials: J
authors.lastname: Dargel
authors.affiliation: Medizinische Fakultät, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225, Düsseldorf, Deutschland.
authors.forename: L
authors.initials: L
authors.lastname: Pennig
authors.affiliation: St. Vinzenz-Krankenhaus Düsseldorf, Schloßstraße 85, 40477, Düsseldorf, Deutschland.
authors.forename: C
authors.initials: C
authors.lastname: Schnurr
authors.affiliation: Klinik und Poliklinik für Orthopädie und Unfallchirurgie, Uniklinik Köln, Joseph-Stelzmann-Straße 9, 50931, Köln, Deutschland.
authors.forename: C K
authors.initials: CK
authors.lastname: Boese
authors.affiliation: Klinik und Poliklinik für Orthopädie und Unfallchirurgie, Uniklinik Köln, Joseph-Stelzmann-Straße 9, 50931, Köln, Deutschland.|Cologne Center for Musculoskeletal Biomechanics, Medizinische Fakultät, Universität Köln, Köln, Deutschland.
authors.forename: P
authors.initials: P
authors.lastname: Eysel
authors.affiliation: Klinik und Poliklinik für Orthopädie und Unfallchirurgie, Uniklinik Köln, Joseph-Stelzmann-Straße 9, 50931, Köln, Deutschland.|Cologne Center for Musculoskeletal Biomechanics, Medizinische Fakultät, Universität Köln, Köln, Deutschland.
authors.forename: J
authors.initials: J
authors.lastname: Oppermann
mesh_terms: D000368:Aged; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging; D000843:Ankle Joint / Q000000981:diagnostic imaging*; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging* / Q000628:therapy*; D056888:Patient Positioning / Q000379:methods*; D017755:Prosthesis Fitting / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: Knee; Knee arthroplasty, total; Leg; Osteoarthrosis; Prosthesis