Hip Joint Replacement

 

Background to hip replacement surgery

 

The operation of total hip replacement is designed to relieve the symptoms of arthritis in the hip. Although it is a very successful operation it is a major procedure and it should be undertaken only for severe symptoms. It is only the patient who knows how severe their pain is but reasonable guidelines are as follows.

 

The surgery is indicated if your hip is preventing you walking for normal day to day purposes due to either pain in the hip or a severe limp. If you cannot walk down the road to the post box or the newsagent or you cannot walk when you are on holiday or you want to go shopping, that is clearly a significant problem. Some people find that surgery is required if the hip is so painful that they cannot sleep at night. In a younger patient it is reasonable to undertake a joint replacement if you cannot go to work because of hip pain.

 

 

What is the hip joint like?

 

The hip joint is the joint between the pelvis and the upper end of the femur or thigh bone. The hip is a ball and socket with the socket in the pelvis and the ball on the upper end of thigh bone. The hip allows both flexion and extension, ie. bending or straightening and also rotation of the joint. The surfaces of the two bones are covered with cartilage which is a shiny white lubricated surface.

 

Although the hip is a ball and socket which is quite stable it does rely on the muscles around the hip joint to stop the ball and socket coming out of the joint or dislocating. For this reason hip replacement can be problematic in people with poor muscle control

 

The process of arthritis in the hip is a destruction of the articular cartilage surface of the joint. This can occur because of childhood abnormalities in the hip caused by unusual types of hip disease or by the development of a very shallow socket in the hip. These abnormally shaped hips tend to wear out in adult life. The cartilage can also be damaged by arthritis. There are two main types of arthritis which affect the hip.

 

Osteoarthritis is a condition in which the articular cartilage wears out. It can be caused by major injuries to the joint. It is more common in people who have had sporting injuries at a young age, but the main cause is genetic. The condition runs in families and it is a common part of the ageing process. Osteoarthritis is nothing to do with osteoporosis which is a thinning of the bones which causes fractures but does not cause arthritis.

 

Rheumatoid arthritis is a disease rather than being a simple wearing out process. In rheumatoid arthritis the lining of the joint is inflamed and it is this inflammation which damages the joint surface. There are other unusual types of inflammatory arthritis similar to rheumatoid arthritis. These include psoriatic arthritis, SLE, Post Parvovirus arthritis and Ankylosing Spondylitis which commonly causes stiffness in the spine as well as arthritis in the hip.

 

How is the joint replaced?

 

The hip joint is opened from the front of the hip using an incision which runs on average around 8 inches over the side of the hip. Muscles are detached from the front of the femur to access the joint and the joint capsule is removed. This allows the ball and socket to be dislocated. The ball or head of the femur is removed. It is usually discarded although we do always keep it until the end of the operation in case the bone is needed.

 

In some patients the head of the femur is kept in a bone bank so that it can be used for bone grafting in other patients. We will not do this without asking your permission. We will not ask for permission in patients with rheumatoid arthritis and related conditions or when the bone banking facility is not available. After the head of the femur is removed the socket is cleaned of arthritic bone and debris to allow the socket to be replaced. If the bone is very hard the socket is replaced with a metal shell which the bone can grow into and this shell has a polyethylene liner. If the bone is more spongy the component is fixed with bone cement. Bone cement is a plastic cement which is mixed from two components. It grouts into the bone and it sets solid in about ten minutes. Over the few months after the surgery the cut surface of the bone regrows in close adhesion to the bone cement.

 

 

A right total hip replacement in a young patient with Juvenile Rheumatoid Arthritis.  The socket was eroded by the arthritis and it has been built up using bone graft taken from the head or ball of the femur.  The socket is an uncemented Trilogy cup made by Zimmer in the USA.  The stem is an Exeter stem, cemented in the shaft of the femur.

 

Having fixed the socket the shaft of the femur is cleared of spongy bone to allow fitting of the femoral component of the hip replacement which has a ball at the upper end.  A trial femoral component is used to check the stability of the joint before the real component is fitted.  When the stability has been checked the femoral component is usually fixed with bone cement.  

 

The hip replacements which I routinely use are the Charnley total hip replacement and the Exeter total hip replacement. The Charnley replacement was the first total hip replacement in the world.  It was developed by Professor Sir John Charnley at Wrightington Hospital in Lancashire.  The Exeter hip replacement was developed by Professor Robin Ling and Dr Clive Lee in Exeter.  Both of these hip replacements have a world beating track record of reliability.  There are some situations where one or other of the replacements is better but most of the time there is little to choose between them. 

 

The risks and benefits of total hip replacement

 

Overall total hip replacement is a very successful operation.  It works well in around 90% of cases in the long term.  The main benefit of the operation is relief of arthritic pain.  Many people who have a total hip replacement feel as if they have a completely normal hip.  In some patients the hip may feel artificial and it may have some minor aches and pains around the joint.

 

The surgery is however a major procedure which has occasional very serious complications.  The complication that we worry about most is infection.  If the artificial hip becomes infected it certainly has to be operated on again and the problem can leave the patient every bit as bad as they were to start off with, particularly if the infection cannot be fully eliminated.  The incidence of infection in routine hip replacements at the Royal Orthopaedic Hospital is around 1%.  The risk is higher in patients with rheumatoid arthritis, diabetes, obesity and other medical problems.  Even so the risk is only around 2%.  There are risks of damage to nerves and blood vessels around the hip.   

 

Another big risk is with the sciatic nerve.  This nerve runs at the back of the hip.  Obviously we know where the nerve is located and it is possible to guarantee not to carelessly cut the nerve.  It can however respond unpredictably to the bruising which one inevitably has following a total hip replacement.  If the nerve is damaged this can cause horrible sciatic pain and weakness in the foot.  To my mind this is actually the most unpleasant complication of hip replacement.

 

There is a risk of the hip coming out of joint.  This is fairly unusual in basically fit patients who have good muscle control.  There is a risk of around 1% in the first six weeks.  The risk is less than that in the long term.  If the hip dislocates it has to be pulled back under an anaesthetic which is obviously extremely tedious for the patient.   

 

The risk to the patient’s life from a total hip replacement is very small but it cannot be totally ignored.  For a fit individual the risk is probably around 0.3%.  The risk is obviously higher in people with medical problems and it is certainly a bit higher in patients over the age of 80.  The main medical complications are heart attacks during or after the surgery and the formation of blood clots in the legs which may float off to the chest with dire consequences.  The risk of this happening is reduced by giving the patient regular doses of Warfarin followed by Aspirin around and after the time of surgery. 

 

Overall therefore the risk of a major complication from the surgery is probably around 2-3%.  

 

If you are a smoker there is an increased risk from the anaesthetic and the surgery which is detailed in the section on smoking.

 

Between the 90% of operations which are very successful and the 2-3% where there is some major problem, there is a group of 5-10% of patients who have a slightly suboptimal result, the procedure is not a disaster but it is spoiled by some problem, particularly the patient may have a detectable limp, they may have pain over the outside of the hip (trochanteric bursitis) or the leg length may not feel quite balanced.  It is common to have a slight difference in the length of the legs after a total hip replacement.  This can be due to correction of a shortening actually caused by the arthritis.  A leg length difference of 1cm is not normally noticed by the patient.  A difference of up to 2cm can usually be accommodated by the patient without much difficulty.  Leg length differences of over 2cm are unusual.  Overall with these various problems the operation is not a disaster by any means but it is not as good as some.

 

In the long term around 90% of total hip replacements are still working ten years after the surgery and I have a lot of patients with well functioning hips between ten and fifteen years post-surgery.  It is a good idea, particularly in a younger patient to have follow-up hip x-rays over the years.  As time goes by the polyethylene in the socket tends to wear out and this can cause loosening of the components as early as ten years post-operation. If a hip becomes loose it can normally be revised but it is best if this is done before there is a lot of bone destruction.

 

Because of the risk of polyethylene wear in total hip replacements selected younger patients are advised to have a hip resurfacing which is similar in many ways to a total hip replacement but it has a very high quality chrome cobalt bearing which, it is hoped, will last much longer in the long term.

 

 

The care of the patient before and after total hip replacement

 

Prior to your surgery it is important that you tell the treating team and the anaesthetist about any medical problems you have and you will be seen at a pre-op assessment clinic for this purpose and to have a full medical check-up.  

 

All patients undergoing total hip replacement surgery have a blood count and their biochemistry checked together with the blood inflammatory markers which are used to monitor the activity of rheumatoid arthritis and check up on infection.  Some patients need their chest x-rays and ECGs done.  Patients with rheumatoid arthritis need to have a neck x-ray prior to surgery as rheumatoid arthritis can cause instability in the cervical spine.  Patients can prepare themselves for surgery by understanding what is going to happen and by keeping as physically fit as possible prior to the surgery, you should therefore do your muscle exercises as much as you can within the limits of the fact that your hip is obviously painful. If you have rheumatoid arthritis your medical management should be optimised by the rheumatologist and the rheumatologist may also treat you with medications such as calcium and bisphosphonates to improve your bone density.  

 

If you are a smoker you should stop.  Smoking certainly increases the risk of a surgical complication following any procedure and total joint replacement is more likely to be problematic in a smoker.  

 

If you are overweight you must reduce your weight.  Weight is calculated using the Body Mass Index (BMI) which gives a reliable measurement of how much you weigh in relation to your height.  Your clinic nurse should be able to calculate your BMI for you using a wall chart.  

 

Your Body Mass Index should be 20 to 25.  If it is 25 to 30 you are overweight. If it is 30 to 35 you are obese and you are better to lose weight.  Once your Body Mass Index is over 35 you are at more serious risk of complications following knee replacement and above a BMI of 40 things are really unacceptably dangerous in my view.  

 

The main risk of being overweight with a total hip replacement is of complications in the early stages.  There is an increased risk of anaesthetic complications due to difficulty with breathing and I think that there is an increased risk of wound healing problems.  There is probably also an increased risk of deep vein thrombosis or blood clots in the leg veins.  

 

The situation with total hip replacement is somewhat different to the situation with total knee replacement.  In a total hip replacement the patient’s weight does not seem to have such an important influence on the long term outcome of the joint, ie. the hip does not seem to wear out purely because of the weight going through it.  It is actually more a matter of the amount of walking which the patient does.

 

Progress after total hip replacement

 

Following the surgery the anaesthetist will have placed a drip in your arm.  You may have an epidural catheter or a nerve block catheter both of which are used to numb the pain in your leg so that you do not have to have such a strong general anaesthetic.  Hip replacement surgery can be done either under a general anaesthetic or an epidural or spinal anaesthetic.  These days it is most commonly done with a combination of a light general anaesthetic and some type of nerve block.  The anaesthetist will usually be happy to comply with the patient’s wishes.  Some people cannot stand the idea of being put completely to sleep but other people cannot stand the idea of a needle in their spine.  There are times when an epidural anaesthetic is better, for example, a patient who has severe chest disease.

 

Following the surgery your skin will be closed with a nylon stitch.  It is possible to use metal clips in the head but I find that, particularly with frail skin, the nylon stitch has a low risk of wound problems.  You will have a dressing over the stitches which is ideally left undisturbed.

 

You will normally get out of bed the day after the surgery with the help of a physiotherapist.  It is quite hard work after a total hip replacement.  The physiotherapist will get you standing initially with help and then with a walking frame.  Once you have mastered walking with the frame the physiotherapist will be keen to get you walking with elbow crutches.  Your walking pattern is much more normal using crutches than it is with a frame.  

 

If you do not have any other medical problems you will normally be on the crutches by around two days after the operation.  In the vast majority of patients the more exercise you can do the better and the more you can toughen up the muscles around the hip and walk, the better.   The physiotherapists should have you walking on the stairs between about three to four days in a fit, younger patient and five or six days in a less fit or elderly patient.  

 

The physiotherapist will tell you how to avoid the hip dislocating.  The way that I do a total hip replacement is through the front of the joint so the joint will normally be stable when you are sitting, provided that this is not in a very low chair, and with your legs slightly apart.  The biggest risk of dislocation is when you are twisting, particularly if you twist away from the hip replacement.

 

Most patients will leave hospital after three to four days if they are local patients who can be supported by the community scheme and possibly a little longer if they come from a long distance or they live alone.

 

Patients with rheumatoid arthritis may have difficulties caused by upper limb problems such as painful shoulders.  If you have painful shoulders and elbows prior to the surgery, if you let us know we can inject these joints whilst you are under the anaesthetic which often helps with post-operative progress.  

 

The skin stitches are removed from the skin at about twelve days, maybe fourteen days in patients with particularly frail skin, on steroids, etc.  By this time you should be mobile around your house with the aid of two elbow crutches and able to get up and down stairs without excessive difficulty.  By six weeks post-operation you should be mobile with one stick and you should be able to drive a car, particularly if it was the left hip that was replaced.  

 

 Swelling in the leg is common after hip and knee surgery. It is important to keep the leg muscles moving and not to leave your foot sitting still on the ground excessively after the surgery. 

 

      For more details on swelling click here. 

 

Limping is also common in the first few months post-surgery

 

     For more details on limping click here.

 

 To get back to driving your car a useful guide is that if you can walk up and down stairs relatively briskly you should be able to drive a car.  The best thing is to take your car to a quiet cul-de-sac and make sure you can do an emergency stop before you set off down the M6.

 

Conclusion

 

Total hip replacement is a major operation.  Most of the time it is dramatically successful and the chances of success are increased by careful attention to detail both from the surgeon, other members of the team and the patient.