In vivo corrosion of CoCrMo alloy and biological responses: a review

In vivo corrosion of cobalt-chromium-molybdenum (CoCrMo) alloy and its potential adverse effects on the body have been recognized as a major concern for its use as biomaterials in recent years. While the underlying mechanism of general and mechanically-assisted corrosion (MAC) related to orthopedic implants have been well-documented and extensive research have been focused on how metal ions and wear particles affect biological response, recent reports of inflammatory cell-induced corrosion (ICIC) on CoCrMo implants have challenged traditional one-way arrow understanding of the relationship between biological system and corrosion, which is 'corrosion causes biological responses', proposing a new concept: biology induces corrosion. This article provides a brief overview on in vivo corrosion of CoCrMo hip implants while focusing on ICIC and new perspective of the two-way feedback loop between corrosion and human body. Recent retrieval studies on ICIC and its clinical relevance will be presented. Biological elements, reactive chemical species and electrochemistry related to the underlying mechanism of ICIC will be discussed.