Early recovery trajectories after fast-track primary total hip arthroplasty: the role of patient characteristics

Sir,—It is with great interest that I read the recently published paper by Porsius and co-workers (Porsius et al. 2018). However, I am worried that the authors may not have obtained a valid estimate of hip function and pain using the Oxford Hip Score (OHS) (Dawson et al. 1996), which the authors define as their main outcome measure. Using the OHS, the authors have assessed hip function and pain 1 week before surgery and every week for the first 6 weeks after surgery in patients recovering from a total hip replacement. However, the OHS uses a recall period of 4 weeks (Dawson et al. 1996). I cannot find information in the paper regarding a potential modification of the originally validated version of the OHS. Could the authors please help explain