In Depth Study Provides Closer Look between Metal on Metal Hip Prostheses and Cobalt-Chromium Toxicity

There is recent interest in the health consequences attributed to metal on metal hip implants and toxic levels of chromium and cobalt released from bearing surfaces and metallic junctions. There are various sources of cobalt and chromium exposure such as occupational and environmental.  Nowadays, concern over cobalt and chromium toxicity is focused on the corrosion of biomedical implants, like metal on metal (MoM) prostheses. The effect of toxicity from these metal ions is dependent on a multitude of factors. For instance, in an industrial setting, toxicity is influenced by the duration of exposure, ion concentration, and entry routes into the body (i.e. skin or respiration). On the other hand, the release of cobalt and chromium ions from MoM devices is an internal exposure rather than external. However, toxicity from MoM implants is contingent on duration of exposure and chemical composition of the implant. According to the article, “It has been determined that these implants release particulate metal debris in the form of corrosion with or without abrasion particles.”

Patients who underwent MoM hip replacement have a range of 5-100 parts per billion of chromium and 5-300 parts per billion of cobalt present in their blood and tissues. In addition, patients also suffer from adverse local tissue reactions (ALTR) and adverse reaction to metallic debris (ARMD) leading to tissue necrosis, pseudotumors, and lesions. The reactions are caused by a combination of metal toxicity and a hypersensitivity reaction. Analysis of tissue recovered from patient with MoM implants revealed necrosis from metal wear debris and corrosion products in the surrounding tissue. Elevated levels of cobalt and chromium ions were also detected in the collected tissue samples in comparison to controls. The study demonstrated a 2.5 fold increase of tissue cobalt levels and a 9 fold increase of tissue chromium levels in patients with MoM hips compared to the controls.

It is natural to have trace amounts of chromium and cobalt because they are required for certain metabolic functions. Glucose metabolism requires chromium to increase the effects of insulin on carbohydrates. Cobalt is involved with Vitamin B12’s biological activity. Only a few specific proteins use the metals and therefore require only trace amounts. However, cobalt and chromium are extremely toxic at high concentrations. The study indicates the effects of cobalt toxicity include irreversible cardiomyopathy, vision or hearing impairments, hypothyroidism, and polycythemia. The effects of chromium toxicity are associated with damage to multiple tissues and kidney and liver failure. Patients implanted with MoM hip prostheses develop an “accelerated inflammatory reaction frequently associated with tissue necrosis and cellular toxicity”. This is known to cause necrotic tissue and formation of pseudotumors.  Furthermore, cobalt and chromium toxicity can interfere and impair certain biological mechanisms and functions and lead to necrotic and apoptotic cell death.

Source: Molecular analysis of chromium and cobalt-related toxicity

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