The ball of the femoral component moves against the inner surface of the socket in a hip replacement. This is the bearing of the hip replacement consisting of 2 bearing surfaces. Conventional hip replacements have consisted of a metal head moving on a plastic cup. This combination may be successful for many years, but, like all bearing surfaces, is subject to wear. Wear is one of the most common causes of failure of total hip replacement. The artificial hip is subjected to millions of movement cycles over the years of it’s lifetime and so it is not surprising that it can wear out. In order to try and reduce wear, new bearing surfaces have been developed and are now under long-term evaluation. Newer plastics have been produced which are highly resistant to wear, but these have not always been very successful in the past.

Ceramic bearing surfaces are extremely attractive for several reasons. Ceramics are extremely hard, very smooth and easily lubricated by the body. Hence they are highly wear resistant and are ideal for long-term hip replacement bearings. In the past, as ceramics can be brittle, there has been a problem with ceramic fracture, but this has largely been eliminated now.

Metal on metal bearings also have extremely low wear rates and are thus potentially also ideal for hip replacement prostheses. However, even though metal on metal bearings do not wear out, they do produce millions of metal particles as they move over the years. These metal particles can cause local allergic reactions in the hip and are transported around the body, being deposited in the lymph nodes and being excreted in the urine in much larger amounts than normal. Concerns exist regarding the safety of these particles and their possible potential to cause tumours. As yet there have been no definite cases of cancer caused by these particles following hip replacement, but concerns persist. In women of child-bearing age we would not advocate metal on metal bearings either as the metal particles do cross the placenta and effects on the unborn baby are unknown.

For these reasons, in the Hip Clinic we favour ceramic bearings as our low wear bearing of choice.

What is Hip Resurfacing?