title: A novel method of accurately calculating the radiological magnification of the hip.
abstract: We have developed a novel method of calculating the radiological magnification of the hip using two separate radio-opaque markers. We recruited 74 patients undergoing radiological assessment following total hip replacement. Both the new double marker and a conventional single marker were used by the radiographer at the time of x-ray. The predicted magnification according to each marker was calculated, as was the true radiological magnification of the components. The correlation between true and predicted magnification was good using the double marker (r = 0.90, n = 74, p < 0.001), but only moderate for the single marker (r = 0.50, n = 63, p < 0.001). The median error was significantly less for the double marker than for the single (1.1% vs 4.8%, p < 0.001). The double marker method demonstrated excellent validity (intraclass correlation coefficient = 0.89), in contrast to the single marker (0.32). The double marker method appears to be superior to the single marker method when used in the clinical environment.
authors.affiliation: University Hospitals Coventry and Warwickshire NHS Trust, Clifford Bridge Road, Coventry CV2 2DX, UK. j.hall@warwick.ac.uk
authors.forename: R J
authors.initials: RJ
authors.lastname: King
authors.forename: P
authors.initials: P
authors.lastname: Makrides
authors.forename: J A
authors.initials: JA
authors.lastname: Gill
authors.forename: S
authors.initials: S
authors.lastname: Karthikeyan
authors.forename: S J
authors.initials: SJ
authors.lastname: Krikler
authors.forename: D R
authors.initials: DR
authors.lastname: Griffin
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D015588:Observer Variation; D011856:Radiographic Image Enhancement / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000379:methods