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Total hip replacement
is one of the most successful treatment interventions in current medical practice. In this operation, the ball and socket
of the natural hip joint are replaced by a prosthetic joint.
A large number of people have hip replacements and this page is intended to help the reader understand hip replacement operations, their advantages and disadvantages, and the limitations.
Arthritis of the hip
The natural hip joint has a socket called the acetabulum, which is a part of the pelvic bone. The top end
of the thigh bone, called the head of femur, is rounded and fits into the socket to form the hip joint. The articulating surface
of the acetabulum and head of femur is lined with a very smooth covering called the articular cartilage.
In arthritis, the articular cartilage becomes thin and wears out. Various conditions can affect the integrity of the articular cartilage. Most commonly, it is osteoarthritis (also called as osteoarthrosis), and other conditions include rheumatoid arthritis, arthritis following injury to the hip, ankylosing spondylitis, arthritis secondary to malformation of the hip, gout, Paget’s disease, and rarely tumours and infections.
Hip replacement is carried out to relieve pain from the degenerate joint.
X ray showing arthritis of the hip joint
Primary or revision hip replacement
The first time the natural hip joint is replaced, it is known as 'primary' hip
replacement. If further operations are required to change one of both components, it is called 'revision' hip replacement.
In a primary hip replacement, the socket is prepared for insertion of an acetabular component, and the head of femur is removed and a femoral component inserted in its place. The two components are fixed into bone either with special bone cement, or by cementless fixation. In cementless fixation, the size and shape of the prosthesis accurately matches the prepared bone and the metal is coated with a special surface which encourages bone ingrowth into the metal, hence providing a firm fixation and long term stability.
Computer navigation for hip replacement surgery
The use of computer navigation for accurate placement of components has been is practice for over 10 years. It improves reliable positioning of the socket and the stem. Navigation is simply a technique, and the actual prosthesis is the same as with conventional technique.
Materials for hip joint
Hip
joint prostheses can be cemented or cementless. The acetabular components in cemented sockets are made of ultra high molecular
weight poly ethylene (UHMWPE). These are fixed to bone with Poly methyl meth acrylate (PMMA) bone cement.
Cementless sockets have a metal backing, like a shell, which is fixed to bone. Within this shell, a (UHMWPE) plastic liner, or a metal liner, or a ceramic liner can be inserted. Cementless sockets allow multiple options for choice of liner. Similarly, the femoral component can be cemented into the thigh bone, or it can be cementless.
Cemented hip replacements have traditionally been used a lot in the past. Currently, cementless hip replacements are increasingly popular.
Hip
replacement surgery is done under general anaesthetic or epidural anaesthetic. Epidural anaesthetic is more commonly used,
and it helps in postoperative pain relief as well.
The operation is done with patients lying on their side. The incision varies between 10cm to 15cm in length and the surgery takes 60 to 90 minutes. Usual hospital stay is between 2 and 5 days.
After surgery, mobilisation is started on the following day. Initially a Zimmer frame is used to help mobility and this quickly progresses to crutches and then sticks. By 6 to 8 weeks, most people are able to mobilise independantly without walking aids, and some may take up to 3 months to regain best mobility.
The physiotherapists will work closely after surgery to improve muscle strength and movements and with progression of exercises, the function in the replaced hip will improve. A list of exercises and precautions is provided, which enables individuals to achieve best possible outcome.
Risks of hip replacement surgery
Hip replacement is, by and large, a reliable and
successful surgery. However, a small number of people may have problems following surgery. The success rate of surgery is
90 to 95% at 10 years.
The potential problems include –
1. Infection in the hip.
Infection in the replaced hip joint is a serious but rare problem and the risk is less than 1%. Superficial infections in the wound present as discharge from the wound, and generally respond to antibiotics and dressing. Deep infection presents as persistent wound discharge, formation of sinus over the wound, or persistent pain. Deep infection may often require revision hip surgery - removal of the artificial hip joint and insertion of a new joint.
The surgery is done in clean air operating theatres, and with use of appropriate antibiotics, the risk of infection is very low (less than 1%). With meticulous surgical technique, strict asepsis and rigourous attention to detail, it is possible to achieve an infection rate near zero.
Infection at the time of surgery is extremely rare. Most of the infections seen in modern practice
are late infections, and these are the result of spread of infection from another site in the body through the blood stream.
2. Dislocation of the hip
The ball of the artificial hip joint articulates with the socket. The socket in most hips joints is hemispherical, and provides the articulation, but does not capture the ball. Accurate positioning of the components, good muscle balance and restoration of normal anatomy at the time of hip surgery prevent dislocation of the ball.
Less than 1 percent people may experience a hip dislocation – which is the ball coming out of the socket. The hip is painful after dislocation, and the leg appears shortened and malrotated. It is not possible to walk with a dislocated hip.
Hip dislocation requires emergency
admission and relocation of the hip joint under anaesthetic. In most patients, the hip is stable afterwards, but one third
of patients having a hip dislocation may require revision surgery.
Modern techniques of soft tissue repair, improved materials and component designs have enabled surgeons to achieve a dislocation rate less than 1%.
3. Deep vein thrombosis and Pulmonary Embolism
Deep vein thrombosis is development of a blood clot in the veins of the calf, thigh or pelvis. This is a risk with any hip or knee surgery and prophylaxis against this provided in the form of tablets or by injections. Foot pumps are provided while patients are in hospital and these mechanically help blood circulation. Current guidlines recommend prophylaxis for 5 weeks after surgery.
Deep vein thrombosis causes swelling of the leg and pain, and temporarily delays rehabilitation following surgery. Clots require treatment with Warfarin.
Pulmonary Embolism is a very rare complication where a clot from the leg travels to the lungs and blocks circulation. Small clots are inconsequential and may not be noticed or detected. Large clots are potentially life threatening.
4. Leg length difference
Arthritis of the hip leads to wear, and a shortened leg. At the time of surgery, it is usually possible to equalise leg lengths. Excess shortening may not be fully correctable. Very rarely, the operated leg may end up being slightly longer. This may be required where the muscle tension in the hip is inadequate and does not support the hip unless stretched. With modern techniques, this is very rare.
Sometimes, the leg may simply feel long, despite being equal. This is because the muscle have been restored their normal lengths. This feeling will subside with time.
5. Limp
Following hip surgery, walking aid in the form of Zimmer frame, crutches and sticks are needed temporarily. As muscle strength improves, the gait improves and by two months, most people are able to walk without sticks. Some people can take a longer time, and this is within normal expected recovery patterns.
6. Rare complications
Rare complications of hip surgery include chest infection, urinary tract infection, or injury to the nerve at the back of the hip (sciatic nerve). In some instances, there may be a crack in the thigh bone during fixation of the femoral component. These are generally detectable and treatable at the same time.
Some people experience swelling of the leg after surgery, which is normal and usually settled within 3 months. Some degree of stiffness of the hip may also be noticed.
The risk of dying as a result of hip replacement is extremely low – risk is a fraction of 1%. Pulmonary embolus, heart attack or stroke, especially with a history of such an event in the past, are the underlying factors for this.
7. Long term complications
In the long term (years), the fixation of the artificial joint into the bone may become loose, or the polyethylene liner may wear out. These situations result in pain and damage to bone around the hip joint. Revision to a new hip joint is required to correct these problems.
Revision of the hip is more extensive operation than the primary surgery and the risk of complications is also higher in revision surgery.
Despite all the risks mentioned
here, most patients (90%) have a speedy and uneventful recovery after hip surgery and do well. 5 to 8% may have a minor complication
which delays rehabilitation, but does not affect the outcome. Only 1 or 2 percent end up with a significant problem. It is
advisable that the surgery is undertaken only when the expected benefit outweighs the potential risks.
New technology and modern implants are helpful, but not a substitute for surgical skill. Some modern implants do not have proven track records and the surgeon endeavours to choose an implant which is safe, reliable and the right choice for the particular patient.
Care after surgery
Following hip replacement, driving is not recommended
for about 6 weeks. The insurance company should be informed about the hip replacement surgery.
Heavy work and lifting heavy objects is not recommended after hip replacement. Running and contact sport are also not recommended. Golf is possible, as is doubles tennis. Riding a bicycle is allowed after 2 to 3 months. Walking is not restricted after hip replacement.
Gardening is limited and many people may experience difficulty in kneeling down and / or sitting in a low seat. This is a permanent restriction.
If there was significant stiffness in the hip prior to surgery, it may be difficult to regain further movement after surgery. This means tying shoe laces and cutting toe nails may be difficult in these situations. There are specific methods which patients are taught postoperatively to manage activities of daily living, and these are part of routine rehabilitation.
These are broad guidelines and individual circumstances dictate rehabilitation for total hip replacement.
If you have further questions, please use the ‘contact
information’ link, and I will be delighted to respond to any comments, questions or concerns.
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