Interfacial membranes collected at revision from 11 failed uncemented Ti-alloy total hip replacements were examined. Particles in the membranes were characterised by electron microscopy, microchemical spectroscopy and particle size analysis. Most were polyethylene and had a mean size of 0.53 micron +/- 0.3. They were similar to the particles seen in the base resin used in the manufacture of the acetabular implants. Relatively few titanium particles were seen. Fragments of bone, stainless steel and silicate were found in small amounts. Most of the polyethylene particles were too small to be seen by light microscopy. Electron microscopy and spectroscopic techniques are required to provide an accurate description of this debris.

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Accelerated corrosion of metallic implants in vivo can generate both soluble and insoluble products that can be detected locally and systemically. Retrieved stainless steel implants for trauma fixation or spinal instrumentation demonstrate iron and chromium-containing solid products of corrosion deposited around corroded modular junctions and as phagocytosable particles in the adjacent tissues. In some cases, the resulting adverse local tissue reaction has been associated with pain, inflammation and osteolysis, requiring removal of the implant. In vitro cell and organ culture studies confirm that corrosion products such as particles of chromium phosphate can elicit proinflammatory cytokine secretion from macrophages and promote macrophage-mediated bone resorption. Systemically, soluble corrosion products of chromium can be detected in the serum of selected patients with accelerated corrosion of chromium-containing implants. Metal-protein binding studies indicate that the high molecular weight serum proteins including immunoglobulins have the highest affinity for chromium. These findings stress the importance of the design of modular junctions to minimize corrosion of stainless steels used in orthopaedic appliances.