The Inadequacy of Short Knee Radiographs in Evaluating Coronal Alignment After Total Knee Arthroplasty

Andrew Park, Jeffrey B. Stambough, Ryan M. Nunley, Robert L. Barrack, Denis Nam

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

Background: Prior studies have associated coronal alignment after total knee arthroplasty (TKA) with implant survivorship. Results have been based on either the femorotibial angle (FTA) on a short knee film or the hip-knee-ankle angle (HKA) on a full-length radiograph. The purpose of this study was to determine if the FTA on short knee radiographs can accurately predict the true HKA alignment after TKA. Methods: Two orthopedic surgeons measured the FTA, HKA, medial proximal tibial angle, and lateral distal femoral angle in 262 patients who had both short and full-length standing radiographs before and/or after primary TKA. Overall coronal alignment was considered neutral if the FTA was between 2.4° and 7.2° on short knee x-rays or if the HKA was between -3° and 3° on full-length films. Results: Preoperatively, 13.9% (26/187) of knees had a neutral FTA on short films, but 50% (13/26) of those were in varus or valgus on full-length films. Postoperatively, 51.4% (106/206) of knees had a neutral FTA on short films, but 27.4% (29/106) of those knees were in varus or valgus on full-length films. When comparing alignment classifications (neutral, varus, or valgus) based on the short vs full-length images, 13.9% (26/187) of patients had discordant classifications on preoperative imaging, and 33.0% (68/206) had discordant classifications on postoperative imaging. Conclusion: A significant proportion of patients were misclassified as varus, valgus, or neutral based on the FTA when compared to the HKA. Short knee x-rays serve as an inaccurate proxy for full-length films when assessing coronal alignment after TKA.

Original languageEnglish
Pages (from-to)878-882
Number of pages5
JournalJournal of Arthroplasty
Volume31
Issue number4
DOIs
StatePublished - Apr 1 2016

Keywords

  • Alignment
  • Full Length Radiographs
  • Mechanical Alignment
  • Short Radiographs
  • Total Knee Arthroplasty

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