60 out of total series of 643 metal-on-metal hip replacements, carried out over the last nine years, have so far required revision, 13 for peri-prosthetic fracture and 47 for extensive, symptomatic, peri-articular soft-tissue changes.

Dramatic corrosion of generally solidly fixed, cemented stems has been observed and is believed to have resulted in the release of high levels of cobalt chrome ions from the stem surface. The contribution of the metal-to-metal articulation is, as yet, unclear.

Not including the fracture cases, plain films have demonstrated little or no abnormality to account for patients’ progressive symptoms. MRI scanning, on the other hand, utilising a technique designed to minimise implant artefact, has correlated very closely with findings at the time of revision surgery.

The histological changes, typified by extensive lymphocytic infiltration and a severe vasculitis leading to, in some cases, extensive tissue necrosis are demonstrated and discussed.

The failure of any of the existing protective mechanisms or regulatory restrictions to identify and limit the exposure of large numbers of patients to unsatisfactory implants has again been demonstrated.