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.