BfR case series of elevated metal levels caused by metal-on-metal implants

Objective: Figures published by German health insurance providers, show that a total of about 200,000 artificial hip joints were implanted in Germany in 2011. Metal-on-metal (MoM) implants have been applied for about 15 years; their construction provokes extreme minimization of the joint line. To reduce wear, special materials such as chromium (Cr), cobalt (Co), nickel (Ni) and molybdenum (Mo) are used. The MoM toxicological problem is the formation of very fine metal debris, depending on the geometry of and strain on joint surfaces. This may sometimes lead to extremely elevated blood concentrations of Co, Cr, Ni or Mo. In some cases, such concentrations may exceed the blood concentrations recorded for example in occupational medicine as well as the respective substantiated limit values. We describe eight cases reported to the BfR-DocCenter (2006-2012). Case series: The individual reports as well as an analysis of cases reported so far under the Chemicals Act §16e were performed, evaluated and recorded in the form of standardised case reports. The existing data were evaluated and assessed regarding possible risks to elevated metal concentrations. The Poison Severity Score (PSS) was used to categorise the health impairment. The causality (exposure versus symptoms/signs) was assessed by the BfR-standard “Three- Level-Model”. All were adult males between 52 and 69 years of age. All had highly elevated concentrations of Co, Cr and Mo above occupational exposure limits. In two cases the MoM-implants were replaced by ceramic implants followed by a successive decrease of the Co, Cr and Mo blood and urine concentrations. The general state of mental health of the patients improved; in one case the lost creative power of a performing artist fully returned. Conclusion: The BfR case series show weak evidence for a negative health impact due to elevated metal concentrations in blood and urine caused by MoM implants based on the BfR “Three-Level-Model”. However, the findings should raise awareness that the source of contamination is located within the body, and it is in direct contact with tissues, blood and lymphatic vessels. Further assessment and investigations should consider that MoM-derived debris may have particle size ranges of fine or even ultrafine (nano) particulate matter.