Revision Hip Replacement
In spite of the generally good results after total hip replacement, there are times when things do go wrong. This fortunately, happens much less frequently now than was the case when hip replacements were first invented. Nearly every hip replacement done within the first couple of years of the operation being devised failed and it did so within two to three years of the surgery. In fact, Sir John Charnley, the inventor of the modern form of hip replacement, was so discouraged that he stopped carrying out the operation until he was able to investigate and fix the problem. He found that the material he was using for the socket (HDP, high density polyethylene) was unsuitable for the purpose and substituted that with UHMWPE (ultra high molecular weight polyethylene). The latter continues to be the most widely used bearing to this day.
When problems arise with a hip replacement, a revision or redo operation may become necessary. The decision about going for surgery is something that has to be made in discussion with the surgeon in charge, taking into account the potential benefits and weighing them up against the risks.
- The most common cause of failure nowadays is loosening of the socket component.
- The femoral component (the “pin” in the thigh bone) seems to do better, but of course that too can loosen.
- There are times when both components may lose fixation.
- Redo or revision hip replacement surgery continues to be neccessary for infection and there generally does not appear to be much improvement in the rates of infection with say the situation 10 years ago.
- Sometimes it is necessary to revise the hip because it is unstable and dislocates or slips out of the joint frequently.
- Relatively rarely, surgery may be required because of bone damage caused by particles generated from wearing down of the replacement. This condition is called osteolysis and some people are concerned that this particular problem may become more frequent in the future.
- In the old days it was not unusual to see the femoral component break from the normal stresses of use, also knows as a fatigue fracture of the implant. This is fortunately a rare occurence with the modern implants.
- Manufacturing errors and design errors can lead to a high rate of failure and early revison surgery. While patients are of course counselled about this likelihood if they happen to have had one of the “problem implants”, surgery is generally delayed until the implants are seen to be clearly failing.