title: Presence of rotational errors in long leg radiographs after total knee arthroplasty and impact on measured lower limb and component alignment.
abstract: Rotation of the lower limb in weight bearing long leg radiographs has a great impact on measured component and lower limb alignment parameters. We asked which rotational errors of long leg radiographs are present in a high volume centre and which radiological and clinical consequences arise regarding measured coronal component and lower limb alignment after total knee arthroplasty.
  
  
  
  In 100 long leg radiographs coronal femoral and tibial component alignment and hip knee ankle angle (HKA) were measured. Present rotational errors in long leg radiographs were determined by fibular overlap and its impact on alignment parameters calculated.
  
  
  
  A mean internal rotation of 8.1° (9.3 SD) with a range between 36° of internal and 16° of external rotation was found in long leg radiographs. This resulted in mean differences between measurements before and after rotational correction regarding femoral and tibial component alignment and HKA of 0.6-0.8° (range 3.5° valgus and 1.6° varus error). Clinically, 11 out of 100 patients were wrongly assigned to either mal- or well-alignment (neutral mechanical alignment within ±3° varus or valgus).
  
  
  
  Surgeons should be aware of potential rotational errors in long leg radiographs after total knee arthroplasty resulting in wrong measurements. In case of rotational errors, radiographs should be repeated or rotational corrections calculated. For study purposes only radiographs after rotational correction should be accepted.
authors.affiliation: Department of Orthopaedic Surgery, University of Regensburg, Regensburg, Germany. Guenther.Maderbacher@klinik.uni-regensburg.de.
authors.forename: Günther
authors.initials: G
authors.lastname: Maderbacher
authors.affiliation: Department of Orthopaedic Surgery, University of Regensburg, Regensburg, Germany.
authors.forename: Clemens
authors.initials: C
authors.lastname: Baier
authors.affiliation: Department of Orthopaedic Surgery, University of Regensburg, Regensburg, Germany.
authors.forename: Achim
authors.initials: A
authors.lastname: Benditz
authors.affiliation: Department of Orthopaedic Surgery, University of Regensburg, Regensburg, Germany.
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Wagner
authors.affiliation: Department of Orthopaedic Surgery, University of Regensburg, Regensburg, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Greimel
authors.affiliation: Department of Orthopaedic Surgery, University of Regensburg, Regensburg, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Grifka
authors.affiliation: Department of Orthopaedic Surgery, University of Regensburg, Regensburg, Germany.
authors.forename: Armin
authors.initials: A
authors.lastname: Keshmiri
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000379:methods; D017760:Bone Malalignment / Q000000981:diagnostic imaging / Q000209:etiology* / Q000601:surgery; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D035002:Lower Extremity / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D012399:Rotation
keywords: Alignment; Knee; Long leg radiographs; Rotation; Rotational error; TKA