Information for Patients

Information for patients photo

3 MY PHILOSOPHY TOWARDS HIP REPLACEMENTS

 

When I trained as an Orthopaedic Surgeon in Oxford and in Bristol, virtually all hips were replaced using bone cement. This provides an interface between the implant and the bone. It was used by Sir John Charnley when he introduced total hip replacements many years ago and still continues being used regularly. I think it is true that it is used more in this country than other parts of the world which may reflect the John Charnley influence in the UK.

 

Twenty years ago I did a Fellowship in Los Angeles and learnt how to put in hip replacements without cement. On returning to Warwick I was keen to adopt a cementless strategy and from 1991 on the acetabular or cup side, I was able to use a cementless fixation. Since 2001 I have used cementless fixation for the stem as well. I believe that we have now good evidence that the cup that I use works well. The cup is called a Pinnacle cup. It has been in use for many years, either in its present form or as its predecessor known as a Duraloc cup. There were only minor modifications made when one changed to the other and therefore we have evidence over 25 years that this cup can be successful. The stem that I choose to use is called a Corail stem. This was designed in 1986 and therefore also has good long term review.

 

the Pinnacle cup and the Corail cup.

I think it is important that good stable fixation is obtained between the host bone and the implant and I think this is true irrespective of the age of the patient, his or her body shape and his or her activities.

 

I think the weak part of the joint replacement has been the bearing surface. Wear of the bearing over a prolonged period of time may cause the hip to fail. I think it is therefore the bearing that needs to be modified according to the patient's demand rather than the whole implant.

 

The bearing surface designed by John Charnley was a polyethylene cup with a metal ball. This has worked well for many people over many years, but in the higher demand patient the polyethylene will wear significantly. One development has been to make the polyethylene harder wearing and now improved polyethylene wears at only one-fifth of the rate of its predecessors. Alternatives however have been to use ceramic balls against ceramic or metal liners.

I have also been very keen to reduce the soft tissue trauma that occurs during a hip replacement. Most hip replacements that I now do are carried out through 12 cms incisions with minimal soft tissue trauma. The length of the incision is actually not so important as the handling of the soft tissues around the hip. The advantages of this may be seen by the patient to be a smaller scar, but from my point of view the significant advantage is minimal soft tissue trauma around the hip joint and good reconstruction of any cut soft tissues at the end of the operation.