So, hip replacement is a very successful operation for the majority of patients. By three months,
most patients can return to their normal activities and have almost forgotten that they've had
the surgery performed. In the long term, the success is equally good. At ten years, more
than 90 percent of patients can expect to still have a successfully functioning hip
replacement and even at 20 years, up to 80 percent of patients can still have a successfully
functioning hip replacements as well.
So the most common reason for a hip replacement to fail is what's called loosening. When a
hip replacement is performed initially, the components of the hip replacement are securely
fixed into the bone. However, over a long period of time, these components can start
to come loose and this can cause pain for the patient. The reason this loosening occurs
is that the bearing of the joint, the ball in the socket can start to wear out over a
period of time and this can release microscopic amounts of particles that can cause an inflammatory
action at the bone and this damages the bone and can cause these components to come loose.
If that becomes severe enough and the pain bad enough, then some patients will require
revision surgeries to replace the worn-out hip replacement. The second most common cause
for failure of a hip replacement is dislocation. This is where the ball jumps out of the socket.
If this happens, the leg is shortened, the patient is in a lot of pain and they're unable
to bear weight. They often have to be transported to hospital in an ambulance and have an anaesthetic
to allow the hip to manipulate it back into place. The highest risk for this is in the
first few months after the surgery whilst the deeper tissues start to heal up. After
this period, the risk of dislocation reduces. Over a long period of time, the risk of dislocation
can then increase again and this can be because either the components are wearing out or the
patient's muscles have become weaker or less coordinated. If a hip replacement dislocates
probably more than three times, then it's likely to keep happening and in this case,
patients may well require revision surgery to try and correct this or prevent this from
happening again. Perhaps the third most common and most devastating cause for a failure of
a hip replacement is if the deep infection occurs around the prosthesis. If microorganisms
settle on the prosthesis and multiply, then deep infection can occur. The period when
this is at the most risk is during actual surgery itself. So great precautions are taken
to prevent this. This can be minimising any medical problems in patients before surgery,
taking great care during the surgery and giving the patient antibiotics at the time of surgery.
In the UK, joint replacement surgery is also performed in ultra clean air operating theatres
to try and minimise this risk. However, if it does happen and deep infection occurs,
then it can be very difficult to eradicate without further surgery. This surgery usually
entails removing the existing prosthesis and then implanting further prostheses. Sometimes
this requires more than one operation.
So, there are less common causes of failure of hip replacement. These can include fracture
of the bone around the prosthesis or even a fracture of the prosthesis itself. These
usually occur many years down the line secondary to wearing of the prosthesis. Another cause
of failure that's occurred in the last few years is failure of metal on metal hip replacements.
Quite a large number of these were implanted in the United Kingdom, between about 2000
and 2010. The metal ions are released from the prosthesis and can cause an extreme inflammatory
reaction in some patients which causes damage to the tissues around the hip or even the
bone itself. If this has occurred, then surgery to remove the metal or metal prosthesis and
insert a different form of prosthesis is almost always required.
So, revision hip surgery is still very successful for most patients but the surgery can range
from a fairly small procedure similar to an initial hip replacement to a very major procedure
requiring extensive reconstruction. So, the most important thing is to try and minimise
the risk of needing revision. There are key things that can contribute to minimising the
risk of revision hip surgery. First is to use implants that have got a proven track
record of long-term success. The second most important thing really is to ensure that the
prosthesis is as accurately placed as possible and to achieve this, it's recognised that
surgeons who perform hip replacement regularly are more likely to be able to achieve this.