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Hip Replacements
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.
"I cant believe the difference the new hip has made to my life. Very happy to be free of pain after suffering for so long"
- John Ellis, Cardiff
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.
Arthritis of the left hip (to the right side of the viewer). Note the loss of normal appearance of Ball and Socket, comparing with the right side, which is normal
X ray appearance after Left side Total Hip Replacement. The artificial hip has a socket which fits into the pelvis and a stem which fixes to the femoral canal.
Surgical approach for hip surgery
I employ a muscle sparing approach for hip surgery, which completely avoids injury to the main abductor muscle to the hip. This is the most important muscle to enable normal walking after hip surgery. As a result, most of my patients are able to discard crutches within 2 to 4 weeks. I have used this approach for over the last many years in hundreds of patients and have been very satisfied with the speedy recovery after surgery, and the ability to achieve normal gait.
The ANTERIOR approach for hip surgery has no evidence in current literature for superiority over any other approach for hip replacement. It has been done in various forms and modifications for over four decades. The risk of complications is slightly higher and hence I do not use this in my practice.
The operation
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 3 days. Over the last 2 years, we have used enhanced recovery program after surgery and this has enabled 40% patients to be discharged from hospital on the day after surgery.
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 4 to 6 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.
In my patients, the risk of infection is extremely low - less than
1 in a 1000 (0.1%)
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%.
Dislocation risk in my patients is 1 in 300 (0.3%)
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.
I use an oral medicine to reduce the risk of blood clots. This is for a period for 4 weeks after hip surgery.
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.
I use an accurate measurement system for assessing leg lengths at the time of surgery, and with that, it is possible to match leg lengths accurately.
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.
I use a surgical approach whereby the main muscles which move the hip joint are not divided or damaged, and as a result, most patients are able to walk normally within 4 weeks.
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 4 to 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.
Through meticulous technique and high standard of care, the
outcome following hip surgery is better than ever
before.
I currently do over 200 hip and knee replacement operations
annually. In my experience, Infection rate following hip
replacement is 0.1%, dislocation rate is 0.3% and the satisfaction
rate after hip replacement surgery is 98%. The percentage of
patients requiring redo operations is 1% at 4 years among all my
patients with hip replacements.
These results are possible through meticulous technique, attention
to detail and careful selection of implants.
If you have further questions, please use the 'About
me’ link, and I will be delighted to respond to any
comments, questions or concerns.