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Objectives and questions: The NeuroWear pilot study demonstrated that Co, Ti, Nb and Zr released from arthroplasty implants may cross the blood-CNS barriers and significantly accumulate in cerebrospinal fluid (CSF). It found merely Co levels to be significantly correlated between blood and CSF. We aimed at elaborating whether CoCrMo components per se are associated with significantly elevated systemic Co and Cr levels.

Material and methods: This single-site hospital-based cross-sectional study was approved by the local ethics committee and prospectively registered.CSF, whole blood (WB) and serum (S) of 102 patients with at least one large joint replacement in situ (implant group) and of 102 age- and sex- matched arthroplasty-naïve patients (control group) were sampled in the course of routine spinal anesthesia or lumbar puncture. Multielement analyses were performed using inductively coupled plasma mass spectrometry and included quantification of Al, Co, Cr, Mo, Ni, Nb, Ta, Ti, V and Zr.Subgroup analyses of patients with at least one CoCrMo component (n=68), patients with arthroplasty implant without a CoCrMo component (n=28),and matched controls were performed. P was set at <0.05.

Results: Subgroup analyses revealed that patients with CoCrMo component/s had significantly higher levels of Co and Cr in WB, S and CSF. In this group, Co levels in CSF were significantly higher in patients with CoCrMo components in situ for both more and less than 10 years. Patients who reported pain in the index joint at the time of sampling exhibited significantly higher Co levels in the CSF. This significant difference was not observed in patients with a pain-free index joint.Patients with CoCrMo-free arthroplasty implants had significantly higher Ti levels in S and Ni levels in WB as compared to controls. No metal concentrations were found to be significantly higher in the CSF of those patients. Patients with arthroplasty implant/s without CoCrMo component/s did not exhibit significantly higher levels of Co and Cr in any of the biological matrices analyzed. Stratification of the implant group based on the individual index arthroplasty implants indicates that patients with knee arthroplasty implants are particularly exposed to Co in the bloodstream. However, both patients with hip and those with knee arthroplasty implants exhibit significantly higher Co levels in CSF compared to controls.

Discussion und conclusion: In CSF of patients with CoCrMo component/s, Co and Cr were found to be significantly higher than in matched controls.This emphasizes that the use of the CoCrMo alloy bears the risk of CNS exposure to arthroprosthetic metals. In view of the neurotoxic potential of Co, this should be considered particularly in patients with new-onset neurological or psychiatric disorders following arthroplasty.