title: The final follow-up plain radiograph is sufficient for clinical evaluation of polyethylene wear in total hip arthroplasty. A study of validity and reliability.
abstract: OBJECTIVE
  Radiostereometric analysis (RSA) is a highly accurate tool for assessment of polyethylene (PE) wear in total hip arthroplasty (THA); however, PE wear measurements in clinical studies are often limited to plain radiographs. We evaluated the agreement between PE wear measured with PolyWare software, which uses plain radiographs, and by model-based RSA, which uses stereo radiographs.
  
  
  METHODS
  Measurements of PE wear postoperatively and at final follow-up (after mean 6 years) on plain radiographs of 12 patients after cementless THA were evaluated with PolyWare software and the results were compared with those from RSA as the gold standard (Model-based RSA using elementary geometrical shape models; EGS-RSA). With PolyWare, we either used the final radiographic follow-up (PW1) only or both the postoperative follow-up and the final follow-up (PW2).
  
  
  RESULTS
  The 2D mean wear measured (in mm) was 0.80, 1.07, and 0.60 for the PW2, PW1, and RSA method. 2D intra-method repeatability was similar for PW1 and RSA with limits of agreement (LOAs, in mm) of ± 0.22, and ± 0.23, respectively. 2D inter-method concurrent validity was best between PW1 and EGS-RSA with LOAs of ± 0.55. For 2D linear wear measurements, the PW1 method had a clinical repeatability similar to that of RSA.
  
  
  CONCLUSIONS
  PW1 is sufficient for retrospective determination of 2D wear from medium-term wear measurements above 0.5 mm, It alleviates the need for baseline plain radiographs, has a clinical precision similar to that of RSA, and is easy and inexpensive to use.
authors.affiliation: Department of Orthopedics, Aarhus University Hospital, Denmark. maiken.stilling@ki.au.dk
authors.forename: Maiken
authors.initials: M
authors.lastname: Stilling
authors.forename: Kristian
authors.initials: K
authors.lastname: Larsen
authors.forename: Niels T
authors.initials: NT
authors.lastname: Andersen
authors.forename: Kjeld
authors.initials: K
authors.lastname: Søballe
authors.forename: Søren
authors.initials: S
authors.lastname: Kold
authors.forename: Ole
authors.initials: O
authors.lastname: Rahbek
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D019544:Equipment Failure Analysis / Q000379:methods*; D005270:Femur Head / Q000000981:diagnostic imaging; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D020959:Polyethylene; D011475:Prosthesis Failure; D011859:Radiography; D015203:Reproducibility of Results; D012984:Software; D013997:Time Factors
chemical_list: D020959:Polyethylene