Metal on metal prostheses were reintroduced for total hip replacements mainly for younger people because they were associated with greater hip stability, preserved the femoral neck and part of the femoral head, and consequently optimized stress transfer to the femur 1.
However recent studies have shown failure rates of 16 % by 10 years post implantation. Failure is commonly associated with granuloma formation (metal on metal pseudotumor) that is thought to be due to soft tissue reaction to nanometer sized metal particles 1.
In many countries, these prostheses have now been withdrawn from the market.