FRETTING IN ORTHOPEDIC IMPLANTS - A REVIEW

Metallic implants in the human body are widely used in surgery, and their corrosion and degradation processes are being extensively investigated around the globe. As with other structural components, possible mechanisms of failure in orthopaedic implants are: mechanical fracture, wear and corrosion, or, more importantly, combinations of these factors. Many implants are exposed to high loads and intense wear, which, as a consequence of the patient's movements, are repeated an immense number of times. The consequent degradative effect on the metals is greatly increased by the fact that the surrounding body-fluid environment is corrosive. Considering the high human cost of revisional surgery and the fact that even ''small'' amounts of corrosion products released into the body tissue are unacceptable, it is clear that the nature and distribution of corrosion products released into the body from orthopaedic implants remains an important issue. Modular implants are being developed, and fretting corrosion/wear are potential degradation problems. They play a deleterious role in the degradation process of the articulating implants by producing fretting debris, which can be detrimental to body tissues and will significantly reduce the performance of the implants. Therefore, this paper reviews the mechanisms of fretting and fretting fatigue that accelerate the fatigue failure of orthopaedic implants, and also presents a state-of-the-art review of the investigations carried out by many workers on this subject.