Corrosion and ion transfer from porous metallic alloys to tissues

Investigations on porous and nonporous alloys currently available for surgical implant device stabilization through tissue ingrowth have shown microstructures that are characteristic of the thermal processing history of the device and alloy with differences between the nonporous and porous devices of the same nominal chemical analysis, in vitro corrosion potentials that are similar for porous and nonporous alloys and corrosion rates that are approximately proportional to the increases in relative surface areas (X 2 to X 10); local tissue interactions at the cellular level that are specific to the type and amount of elemental constituents present at the interface; and no direct correlations between the local cellular responses (fibroblasts) and the potential for hypersensitivity and other systemically mediated responses. Evaluations of the available published literature and available information on device retrievals and analyses support the opinion that no quantitative, statistically based epidemiologic studies have yet established significant correlations between selected metallic ions and major types of tissue lesions. However, with the changes in surface area and basic surface chemistry for existing alloy systems, research on the long-term tissue responses should be emphasized. In our opinion, biomaterial surface modifications are possible, whereby the relative quantities of released ions available to the environment could be significantly reduced.