Metal ion release into the body is an inevitable consequence of any implanted metal device. An

example of metal implants consists the current generation of metal-on-metal (MoM) hip

prostheses, which are predominantly comprised of cobalt and chromium. Excessive bodily uptake

of cobalt ions, formed by friction and corrosion processes between the metal surfaces, may cause

adverse local tissue reactions (e.g. necrosis, inflammation) as well as systemic toxic reactions. The

condition of systemic cobalt toxicity from MoM hip prostheses has been denominated

arthroprosthetic cobaltism and seems to manifest as a clinical syndrome with a variable set of

cardiac, endocrine and neurological symptoms, including tinnitus, hearing loss and vertigo.

Currently, there are no objective methods to relate the cobalt ion concentration in the blood with

altered functioning of different physiological systems. Consequently, no internationally accepted

cut-off criteria exist for the detection of systemic cobaltism. Given that the auditory and vestibular

structures are highly sensitive to detect drug-related toxicity, they might contribute to the early

detection of systemic cobaltism. Therefore, we aim to study the mechanism of how cobalt ions

degrade the auditory and vestibular function, using the model of MoM hip arthroplasty, in order

to define objective biomarkers of cobaltism by means of advanced measurements of the auditory

and vestibular function.