FRETTING IN ORTHOPEDIC IMPLANTS - A REVIEW

Metallic implants in the human body are widely used in surgery, and th eir corrosion and degradation processes are being extensively investig ated around the globe. As with other structural components, possible m echanisms of failure in orthopaedic implants are: mechanical fracture, wear and corrosion, or, more importantly, combinations of these facto rs. Many implants are exposed to high loads and intense wear, which, a s a consequence of the patient's movements, are repeated an immense nu mber of times. The consequent degradative effect on the metals is grea tly increased by the fact that the surrounding body-fluid environment is corrosive. Considering the high human cost of revisional surgery an d 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 orthop aedic implants remains an important issue. Modular implants are being developed, and fretting corrosion/wear are potential degradation probl ems. They play a deleterious role in the degradation process of the ar ticulating implants by producing fretting debris, which can be detrime ntal 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 orthopaed ic implants, and also presents a state-of-the-art review of the invest igations carried out by many workers on this subject.