Figure 1.

Digital optical micrographs (DOM) of different retrieved CoCrMo hip implants with evidence of inflammatory cell induced (ICI) corrosion. Implants were hips and knees and both metal-on-polyethylene (MOP) and metal-on-metal (MOM) devices, with different metallurgical conditions (wrought and cast). A) low magnification DOM image of the rim of a metal acetabular liner component with a frosted appearance that is visual evidence of ICI corrosion (Bar = 5 mm). B) A higher magnification image of the head bearing region of a MOP couple showing multiple spots of ICI corrosion (bar = 250 µm). C) An optical micrograph from a knee implant (cast CoCrMo and MOP bearing) showing the nature of the corrosion attack resulting from inflammatory cells. This attack was located on the posterior condular surface of the femoral component (bar = 100 µm). D) DOM image of a MOM head with ICI corrosion patterns. E) Higher magnification DOM image of the head in D showing isolated cell attack regions (Arrows). F) Higher magnification DOM image of the MOP head in B with specific cell-attack regions (Arrows). There are several common features in these images. First, patterns are all on the 10 to 100 um length scale consistent with cellular dimensions and individual cell corrosion spots (see arrows in 1E and 1F) which have a central flat smooth oval or circular crater-like spots surrounded by a frosted pattern of ruffled topography. Some images show single roughly circular spots of attack while other regions appear to result from either larger single cells, multiple cells or single-moving cells attacking the CoCrMo surface.