Co and Cr accumulation in hair after metal-on-metal hip resurfacing arthroplasty.

Background: Currently, it is unclear whether Co and Cr levels are persistently elevated in the body after hip resurfacing arthroplasty (HRA). This study aimed to evaluate Co and Cr levels in the body after HRA using hair as samples.

Methods: Among 22 patients who had metal-on-metal HRA(m-o-m group) using the DePuy ASR system, scalp hair of 1.5 cm in length and 2 g in weight was collected before and at 6 and 12 months after surgery. Inductively coupled plasma-mass spectrometry (ICP-MS) was used to detect Co and Cr levels in the scalp hair. Another 22 patients with total hip replacements were randomly selected from a similar age range as controls (m-o-p group). Metal levels in hair were detected with multiple measurements and analysed by repeated measures analysis of variance.

Results: Both Co and Cr levels were significantly increased in the m-o-m group after surgery compared with those in the m-o-p group (P < 0.01). Co levels at 6 months post-operatively were 12-fold those before surgery, and Co levels 12 months postoperatively were lower than those at 6 months, but this difference was not significant (P = 0.0805) between the two time points in the m-o-m group. Cr levels were persistently elevated after surgery and were increased by 10-fold compared with those at baseline in the m-o-m group.

Conclusions: Co and Cr levels in scalp hair are ideal indicators for metal levels in the body after HRA. Co and Cr levels in the body were greatly increased after metal-on-metal HRA. Long-term accumulation of these metals needs to be further investigated