Response to Letter to the Editor concerning “How symmetric are metal-on-metal hip resurfacing patients during gait? Insights for the rehabilitation”

Between the studies demonstrating that higher blood metal ion levels were associated with higher revision rate and higher ALTR, the most commonly used threshold for high metal ions was 7µg/L (Hart et al., 2014; Cip et al., 2014; Fox et al., 2014; Malek et al., 2012). [...]our participants had low metal ion levels, which along with their low hip pain and stiffness intensity and high physical function (Resende et al., 2017), suggest that they did not have failing hips. [...]our sample size was defined based on the effect sizes of the differences in hip biomechanics between sides found during a pilot study with five participants, as described in the methods section. [...]our sample size was appropriate for the purposes of the study. [...]it should be noted that a larger sample (i.e. 114 participants), operated by the same surgeon or by a colleague, using the same equipment and procedures, also demonstrated high functional levels at a mean follow-up time of 4.5years (Mann et al., 2017), which suggests that our sample appropriately represent a greater number of hip resurfacing patients.