“…As discussed later, however, various severe pitfalls and possible inherent error or bias must be considered. As with total knee arthroplasty and screw positioning in spinal surgery, the major benefit of navigation is the reduction of outliers, that is, cup positioning beyond the “safe zone” with an inclination of 40° (± 10°) and anteversion of 15° (± 10°) (Saxler et al 2004a, Honl et al 2006, Kalteis et al 2006a, Minoda et al 2006, Leichtle et al 2007, Parratte and Argenson 2007, Sugano et al 2007). Moreover, it seems that navigation-based cup positioning in THA meets the criteria of evidence by reducing the amount of outliers in cup orientation (Leenders et al 2002, Stipcak et al 2004, Ottersbach and Haaker 2005, Kalteis et al 2006a, Parratte and Argenson 2007).…”