TABLE OF CONTENTS Stainless steel is the name given to a range of steels that include elements other than iron and carbon, which passivate the metal against corrosion. Typically, the passivating element is chromium which, under normal conditions, forms an adherent, tenacious oxide coating, through which water and oxygen cannot permeate, and hence which prevents corrosion. The main biomedical grade of stainless steel is called Type 316L and it is popular for use as osteosynthesis plates in orthopaedic applications.45 This popularity arises from a satisfactory combination of good mechanical properties and acceptable cost.
Although type 316L stainless steel shows a relatively low corrosion rate under external conditions, within the body it will undergo corrosion at a more rapid rate.46 ,47 This is because the natural surface oxide coating is not stable on exposure to physiological fluids, and both crevice and pitting corrosion are therefore able to take place within the body.48 Even after times of implanation as short as two months there is clear evidence of crevice corrosion with this material.49 This corrosion, or pitting corrosion, rarely occurs to such an extent that the implant fails mechanically. On the other hand, it necessarily occurs with release of ions into the surrounding tissues. For example, the in vitro corrosion of stainless steel in physiological solutions has been shown to release the toxic ions Cr 6+, Ni 2+ and Mo 6+, as well as the more benign Fe 3+, and in a series of cytotoxicity tests...
