Replacement hips

SIR – The history of metal-to-metal hips is part of the still developing story of hip replacement.

The original implants of cobalt chrome were abandoned because of the superior results of Sir John Charnley’s metal to polyethylene design. Charnley himself envisaged using these hips only for elderly patients, because he was aware of the effect of the polyethylene wearing, and also of the potentially destructive effects of the breakdown products.

Hip disease is not a problem of old age, and usually stems from (sometimes subtle) mechanical problems caused by genetic or developmental influences. Many patients in the most active parts of their lives have severe pain. It was for them that hip surgeons returned to hard-to-hard bearings, in the hope that new materials technology would obviate the problems of the past.

Ceramics work well, but often squeak in use, and cannot be used for the resurfacing designs which have been popular. Polyethylene does not function well at all in a resurfaced hip.

It was, therefore, despite awareness of the shortcomings of the past, that hip surgeons turned again to metal bearings. We were assured by the engineers that they had overcome the faults of the earlier generation. Sadly, they were mistaken. David Nunn FRCS

West Malling, Kent