Orthopedic Implant Fretting Corrosion

Fretting corrosion occurs to some extent on all load bearing metallic orthopedic implants. Fretting of total hip and knee replacements occurs at such places as the bone-stem interface, the stem-cement interface, and on the interfaces of modular connections between implant components. Fretting also occurs at areas of cyclic load bearing contact on metallic bone-plates and screws, such as screw-plate connections, bone-plate interfaces and screw-bone interfaces. Of primary clinical concern is the generation of ionic and particulate debris through fracture and abrasion of the metal oxide protective layers covering implant alloys /1/. This debris produced locally within crevices of component connections can migrate away from junctions and cause injury both systemically and in the local tissue. Clinical concern about the release and distribution of metallic degradation products is justified by the known potential toxicities of the elements used in modern orthopedic implant alloys (titanium, aluminum, vanadium, cobalt, chromium, molybdenum and nickel) and known pathologies associated with metal implant degradation (i.e. hypersensitivity, particle induced inflammation, etc.) /2/. However, little is known of the short and long-term biologic impact of soluble metal-protein complexes formed from the degradation products of implants.