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The validity of a non-radiologist reader in identifying cam and pincer femoroacetabular impingement (FAI) using plain radiography

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The purpose of this study was to evaluate the validity and reliability of a radiographic diagnosis of femoroacetabular impingement (FAI) by a non-radiologist. Symptomatic FAI is prevalent and thought to be a cause of hip osteoarthritis. However, the diagnosis is often delayed by 1–2 years, in large part because radiographic findings are often subtle and clinicians have been unaware of their significance. The purpose of this study was to evaluate the validity of a radiographic diagnosis of FAI by a non-radiologist. A population-based sample of 701 subjects was recruited in Vancouver, Canada. For the current study, 50 subjects were selected—40 randomly from the population sample and 10 from an orthopedic practice with confirmed FAI. An anterior–posterior pelvis and bilateral Dunn radiographs were acquired and read by a fellowship-trained musculoskeletal radiologist and a third-year medical student who received basic training in radiographic signs of FAI. Three radiographic signs were evaluated: the lateral center edge angle, alpha angle and crossover sign. Validity was assessed using sensitivity and specificity, Bland–Altman limits of agreement and kappa. The sample contained 65 % women (n = 31), was 62 % Caucasian and 38 % Chinese and had a mean age of 38.3 years. For correctly diagnosing FAI, the non-radiologist reader had a sensitivity of 0.83 and specificity of 0.87. Intra-rater κ value was 0.72, and prevalence-adjusted bias-adjusted κ was 0.76. This study provides evidence that a non-radiologist can accurately and reliably identify FAI on plain films.

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The protocol for this study was approved by the Clinical Research Ethics Board at the University of British Columbia. This study was supported by the Canadian Institutes of Health Research (107513).

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Correspondence to C. Ratzlaff.

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Ratzlaff, C., Zhang, C., Korzan, J. et al. The validity of a non-radiologist reader in identifying cam and pincer femoroacetabular impingement (FAI) using plain radiography. Rheumatol Int 36, 371–376 (2016).

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