We read the comments of Bachhal et al. with interest regarding our article entitled “Assessment of inter- and intra-observer reliability in the determination of radiographic version and inclination of the cup in metal-on-metal hip resurfacing” [1]. They state that our method to measure version in MMHR is not the easiest. Further, they present a simplified method including only two measurable variables. We fully agree with the comments of Bachhal et al. Our method is in no way the easiest method to measure version. Our method can be simplified step-wise to the one which Bachhal et al. present. Actually, Widmer has shown this simplified method to be reliable in the measurement of version in THR [2]. However, we wanted to make our method as generalised as possible since not all MMTHR cups are hemispherical on the outer contour. In non-hemispherical cups version measurement can only be performed with the aid of the ellipse formed by the cup opening.

The method of Bachhal et al. should certainly be used when version is defined in hemispherical cups (i.e. Birmingham Hip Resurfacing, Smith & Nephew, UK), since it is more straight-forward to perform. However, assessment of version in non-hemispherical MMTHR and MMHR cups requires a more complicated method.