title: Reliability of various observers in determining common radiographic parameters of adult hip structural anatomy.
abstract: BACKGROUND
  Radiographic evaluation of the hip is extremely important in the diagnosis and treatment decisionmaking process for pre-arthritic hip disease. Many different radiographic measurements have been described as indicators of underlying structural hip deformity. The purpose of this study was to determine the interobserver and intraobserver reliability of various musculoskeletal physicians in performing selected measurements of adult structural hip anatomy.
  
  
  METHODS
  A blinded review of 45 sets of radiographs from patients with developmental dysplasia, femoro-acetabular impingement, and normal anatomy was performed. Data points included the lateral center-edge angle (LCEA), vertical-center-anterior angle (VCA), head-neck offset ratio (UNO), alpha angle, Tönnis angle, Tönnis osteoarthritis grade and a radiographic diagnosis. One orthopaedic fellow, two orthopaedic residents, and two attending musculoskeletal physiatrists analyzed radiographs on two separate occasions. One sports medicine orthopaedic attending physician completed a single analysis of the image sets. Intraobserver and interobserver reliability was established using intra-class correlation coefficients (ICC) for continuous variables. Agreement regarding categorical variables was performed using the kappa coefficient
  
  
  RESULTS
  Excellent intraobserver reliability was found for the following: LCEA (ICC = 0.88), VCA (0.88), Tönnis angle (0.83), HNO on the frog lateral (0.78), alpha angle on the frog lateral (0.76), HNO on the cross-table lateral (0.75), and angle alpha on the cross-table lateral (0.76). Intraobserver reliability for osteoarthritis grade was poor (weighted kappa = 0.57). For all data points, interobserver reliability was considerably worse, with 95% confidence intervals spanning below 0.55.
  
  
  CONCLUSIONS
  While the described measurements of adult structural hip anatomy provide excellent reliability for a given reader, these measurements are less reliable across readers. Taken in isolation, these measurements, as performed by observers with varied clinical experience and clinical backgrounds, are limited in determining a consistent radiographic diagnosis.
authors.affiliation: Department of Orthopaedic Surgery, Washington University School of Medicine, St Louis, MO, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Carlisle
authors.forename: Lukas P
authors.initials: LP
authors.lastname: Zebala
authors.forename: Derek S
authors.initials: DS
authors.lastname: Shia
authors.forename: Devyani
authors.initials: D
authors.lastname: Hunt
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Morgan
authors.forename: Heidi
authors.initials: H
authors.lastname: Prather
authors.forename: Rick W
authors.initials: RW
authors.lastname: Wright
authors.forename: Karen
authors.initials: K
authors.lastname: Steger-May
authors.forename: John C
authors.initials: JC
authors.lastname: Clohisy
mesh_terms: D000077:Acetabulum / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D000328:Adult; D001175:Arthrography / Q000592:standards* / Q000706:statistics & numerical data*; D016208:Databases, Factual / Q000706:statistics & numerical data; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging* / Q000473:pathology; D006617:Hip Dislocation / Q000000981:diagnostic imaging* / Q000473:pathology; D006621:Hip Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D006801:Humans; D015588:Observer Variation; D009985:Orthopedics / Q000592:standards* / Q000706:statistics & numerical data; D010820:Physicians / Q000592:standards / Q000706:statistics & numerical data; D015203:Reproducibility of Results
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