Metal on metal bearings. A practical alternative to metal on polyethylene total joints?

Metal on metal articulation is proposed as an alternative to metal on polymer in total hip replacement arthroplasty as a technical means of reducing wear debris production and subsequent osteolysis leading to the need for surgical revision. The question of whether metal on metal articulation is a practical alternative to current practice is essentially that of whether it is as safe as, and more effective than, metal on polymer articulations in use for more than 20 years. Unfortunately, the metal on metal articulation introduces additional biologic risks associated with production of increased metallic corrosion and wear products. The clinical longevity and success of metal on polymer articulation in total hip replacements, as embodied in the Charnley type, is such that it may prove humanly impossible to determine that metal on metal articulations are more effective, even if that is objectively the case. Therefore, it is suggested that, consistent with modern technical and ethical standards, it cannot be concluded that metal on metal articulation is a practical alternative to current metal on polymer designs. It is suggested that future improvement in total hip replacement arthroplasty outcome is more likely to be through evolutionary than revolutionary designs.