title: Inter-observer and intra-observer reliability of mechanical axis alignment before and after total knee arthroplasty using long leg radiographs.
abstract: BACKGROUND
  Long leg radiographs (LLRs) are commonly performed for assessment of mechanical alignment and operative planning in patients undergoing total knee arthroplasty (TKA). The aim of this study was to determine the inter- and intra-observer reliability of alignment measured by observers of different levels of experience.
  
  
  METHODS
  Forty patients on the waiting list for a TKA had pre- and post-operative standardised LLRs. We analysed the measurements of mechanical axis alignment between an orthopaedic surgeon, a senior orthopaedic registrar, a junior orthopaedic registrar, and a medical student. Reviewers performed blinded measurements on the same computer screen. These measurements were repeated three months later to assess intra-observer reliability. Furthermore high-resolution screens were compared with standard hospital computer screens to investigate whether monitoring quality influenced the accuracy of measurements of alignment.
  
  
  RESULTS
  Inter-observer reliability was high for pre-operative LLRs with an intra-class correlation (ICC) of >0.9 at all experience levels. Post-operative ICC was lowest between the surgeon and the medical student at 0.7. Intra-observer reliability was high at all experience levels. Larger deformities appeared to have exaggerated measurements for both pre- and post-operative images. There appeared to be no effect of the monitor size and quality on the accuracy of measurement.
  
  
  CONCLUSIONS
  Long leg radiographs can be used to measure mechanical axis alignment with strong reliability across different levels of experience. This information is important for the evaluation of knee alignment measurements in current clinical practice, to assess severity of deformity and to accompany pre-operative planning and post-operative evaluation.
  
  
  METHODS
  III.
authors.affiliation: Department of Orthopaedics, School of Medicine, Flinders University, Adelaide, Australia; International Musculoskeletal Research Institute, Repatriation General Hospital, Daws Road, Daw Park, SA, Australia.
authors.forename: Anneka
authors.initials: A
authors.lastname: Bowman
authors.affiliation: Department of Orthopaedics, School of Medicine, Flinders University, Adelaide, Australia.
authors.forename: Meenalochani
authors.initials: M
authors.lastname: Shunmugam
authors.affiliation: Department of Orthopaedics, School of Medicine, Flinders University, Adelaide, Australia; International Musculoskeletal Research Institute, Repatriation General Hospital, Daws Road, Daw Park, SA, Australia. Electronic address: amyrosewatts@gmail.com.
authors.forename: Amy R
authors.initials: AR
authors.lastname: Watts
authors.affiliation: Department of Orthopaedics, School of Medicine, Flinders University, Adelaide, Australia; International Musculoskeletal Research Institute, Repatriation General Hospital, Daws Road, Daw Park, SA, Australia.
authors.forename: Donald C
authors.initials: DC
authors.lastname: Bramwell
authors.affiliation: Department of Orthopaedics, School of Medicine, Flinders University, Adelaide, Australia; International Musculoskeletal Research Institute, Repatriation General Hospital, Daws Road, Daw Park, SA, Australia.
authors.forename: Christopher
authors.initials: C
authors.lastname: Wilson
authors.affiliation: Department of Orthopaedics, School of Medicine, Flinders University, Adelaide, Australia; International Musculoskeletal Research Institute, Repatriation General Hospital, Daws Road, Daw Park, SA, Australia.
authors.forename: Jeganath
authors.initials: J
authors.lastname: Krishnan
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery; D007720:Knee Prosthesis; D007866:Leg / Q000000981:diagnostic imaging*; D008297:Male; D015588:Observer Variation; D011184:Postoperative Period; D057234:Preoperative Period; D017755:Prosthesis Fitting; D011859:Radiography / Q000379:methods*; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted / Q000379:methods*; D016474:Weight-Bearing / Q000502:physiology*
keywords: Alignment; Inter-observer reliability; Intra-observer reliability; Long leg radiograph; Total knee arthroplasty