DISCUSSION
rigidity, femoral head
In the present study of primary THAs we found no difference in blood ion levels with the use of Oxinium femoral heads compared to CoCrMo or stainless steel heads at 10 years follow‐up. To our knowledge this is the first RCT who compares metal ion release from these three femoral head materials.All the Co and Cr values were well below the British Medicines and Healthcare Products Regulatory Agency threshold value of 7 μg/L. All the median Co and Cr values for the three head materials were similar and all below 0.3 μg/L. This is actually comparable with preoperative blood metal values measured with the same methodology as in our recent study, where we found median Cr and Co concentrations of 0.23 μg/L and 0.14 μg/L, respectively, in a cohort of patients measured prior to receiving Birmingham hip resurfacing prostheses.The mechanisms of trunnionosis are currently poorly understood and is likely multi‐factorial.One study has suggested that by using a ceramic femoral head, CoCrMo tribocorrosion may be mitigated.Mid‐term in vivo wear results (2‐ and 5‐year follow‐up based on radiostereometric analysis [RSA]) have not shown wear benefits of Oxinium femoral heads over conventional CoCrMo femoral heads.Furthermore, it is now well established that highly cross‐linked polyethylene acetabular cups and liners significantly reduces wear compared to conventional polyethylene.Neck taper flexural rigidity also affect trunnion corrosion and one study showed that lower stem flexural rigidity predicted stem fretting and corrosion damage in a ceramic head cohort, but not in the metal head cohort.