A total knee replacement (TKR) or total knee arthroplasty is an operation in which an arthritic knee joint is resurfaced with artificial metal and plastic replacement parts called the 'prostheses'.
The procedure is usually recommended for older patients who suffer from pain and loss of function from arthritis, and when other conservative methods of therapy have failed. It may be useful in some younger patients, particularly with inflammatory arthritis.
Modern knee replacements rely on resurfacing the worn out joint surface whilst preserving the patient's own ligaments, to allow the replacement to move as close as is possible to a normal knee joint.
Occasionally realignment operations such as an osteotomy may avoid the need for a total knee replacement and on occasions if only one part of the knee joint is severely worn then uni-compartmental or patello femoral replacement surgery is recommended rather than TKR.
The typical knee replacement replaces the ends of the femur (thigh bone) and tibia (shin bone) with metal components and has plastic inserted between them. The patella ("knee-cap") may or may not also be resurfaced.
The decision to proceed with TKR surgery is a co-operative one between you, your surgeon, your family and your GP.
The risks associated with this operation these will be discussed with you by your Consultant. - For most patients it is a highly successful procedure, providing pain relief and improving mobility.
Before the operation
You will need to attend a Pre-operative Assessment appointment, usually 2-3 weeks before your planned operation. - A series of routine investigations will be organised there. These usually include blood tests, X-rays, an ECG (heart tracing), urine tests and screening swabs for MRSA.
Depending on your general medical history, you may be asked to undertake an assessment with one of the Anaesthetic Consultants, to ensure you are fit for the operation.
If any changes to your usual medications are necessary before your operation, these will be explained to you.
You will usually meet one of the Occupational Therapists who can discuss any necessary modifications around your home, which may help when you are discharged after your operation.
You will have an opportunity to meet one of the Physiotherapists - An initial assessment is combined with advice on what to expect following surgery in terms of exercises etc.
If you smoke, you should try to stop or cut down for as long as possible prior to surgery.
When you are admitted for your operation, you should be fit for the surgery. - You should not have a cough or a cold, and there should be no sores, cuts or ulcers on your skin.
You will be admitted in the afternoon before surgery if your operation is planned for a morning operation list. If your operation is planned in the afternoon or evening, you may be admitted early that morning.
You should have nothing to eat for at least six hours before your operation. Clear fluids are generally allowed up to four hours beforehand. This will be discussed with you during your Pre-operative Assessment visit.
On the day of surgery
You will meet the nurses and answer some questions for the hospital records.
Further tests may be required on admission.
You will meet your Anaesthetist - the type of anaesthetic best suited to you will be discussed and explained.
You will be given a hospital gown to change into.
Approximately 30 minutes prior to surgery, you will be transferred to the operating theatre.
The surgical procedure
The operation will take between one and two hours.
Surgery is performed under sterile conditions in the operating theatre usually under a spinal anaesthetic. This technique anaesthetises the legs and will usually be combined with a sedative so that you can sleep. It also provides excellent pain-relief post-operatively. For some patients a general anaesthetic is more appropriate.
Each knee is different, and knee replacement components are available in a range of sizes to take account of this.
After surgical exposure of the knee joint, the damaged parts of the bones are removed using a series of angled cuts with the help of specialised jigs. Trial components are used to check the accuracy of these cuts and to determine the thickness of plastic required to place between these components.
The patella (knee cap) may be replaced depending on a number of factors.
The real components are then inserted with or without cement and the knee is again checked to make sure things are working properly.
The knee is then carefully closed and a drain is usually inserted. - The knee is dressed and bandaged.
After the operation
After you wake, you will be in the recovery room with intravenous drips in your arm, a tube (catheter) in your bladder and a number of other monitors to check your vital observations.
Once stable, you will be taken to the ward. The post-op protocol is surgeon dependant, but in general your drain will come out after 24 hours and you will sit out of bed and start moving your knee and walking on it within a day or two of surgery. The dressing will be reduced usually on the first post-operative day to make movement easier. A Physiotherapist will supervise your rehabilitation and mobilisation.
To avoid lung congestion, it is important to breathe deeply and cough up any phlegm you may have.
Your Consultant will use one or more measures to minimise the risk blood clots (DVT's) in your legs. - These may include stockings and injections to thin the blood
Hospital stay is usually 5 - 7 days following surgery. You will need Physiotherapy on your knee following surgery.
You will be mobilising with a walking aid - either a frame or crutches, and then progress to walking sticks.
Your sutures maybe dissolvable but if not arrangements will be made for them to be removed at approx 15 days.
Once the wound is healed, you can take a shower. You can drive at about 8 weeks, once you have regained control of your leg. You should be walking reasonably comfortably by 6 weeks. Advice and instructions on driving etc. will be provided by your Consultant.
When you go home you need to take special precautions around the house to make sure it is safe. You may need rails in your bathroom or to modify your sleeping arrangements if your bedroom is up a lot of stairs.
You will usually have a 6 - 8 weeks check-up with your surgeon who will assess your progress.
If you ever have any unexplained pain, swelling, redness or if you feel unwell you should see your doctor as soon as possible.
Return to sedentary work is usually possible after 10 - 12 weeks.
Return to light sport (e.g. Golf) is usually possible after 10 - 12 weeks but may take longer.
Risks and complications
As with any major surgery, there are potential risks involved. Your decision to proceed with the surgery should be made when you feel that the advantages of surgery outweigh the potential disadvantages.
It is important that you are informed of these risks before the surgery takes place. Complications can be medical (general) or local complications specific to the Knee.
Medical complications include those of the anaesthetic and your general well being. Almost any medical condition can occur so this list is not complete.
General complications include:
Allergic reactions to medications
Blood loss requiring transfusion with its low risk of disease transmission
Complications from nerve blocks such as infection or nerve damage.
Serious medical problems can lead to ongoing health concerns, prolonged hospitalisation or rarely death.
Local complications include:
Infection - Infection can occur with any operation. In the knee this can be superficial or deep. The infection rate after TKR is up to 1% - If it occurs it can be treated with antibiotics but may require further surgery. Very rarely your new knee may need to be removed to eradicate infection.
Blood clots (Deep Venous Thrombosis - DVT) - These can form in the calf muscles and can travel to the lung (Pulmonary embolism - PE). These can occasionally be serious and even life threatening. If you get calf pain or shortness of breath at any stage, you should notify your doctor.
Stiffness in the knee. - Ideally your knee should bend beyond 100° but rarely the knee may not bend as well as expected. Sometimes manipulation is required - This means going to theatre and under anaesthetic the knee is bent for you.
Wear - The plastic liner eventually wears out over time and may need to be changed. If there is significant wear, the metal components may become loosened from the bones and revision surgery may be required.
Dislocation - An extremely rare condition where the ends of the knee joint loose contact with each other or the plastic insert can lose contact with the tibia (shinbone) or the femur (thigh bone).
Patellar problems - The Patella (knee cap) can dislocate that is, it moves out of place and it can break or loosen. This complication is extremely rare.
Damage to nerves and Blood vessels - Rarely these can be damaged at the time of surgery. If recognised they are repaired but a second operation may be required. Nerve damage can cause a loss of feeling or movement below the knee and can be permanent. This complication is extremely rare.
Fractures or breaks in the bone can occur during surgery or afterwards if you fall. To fix these, you may require further surgery.
Overall, Total Knee Replacement (TKR) is one of the most successful Orthopaedic operations available today. It is an excellent procedure to improve people's quality of life, taking away pain and improving function. In general 90 - 95% of knees survive 15 years depending on age and activity level.
Although most people are extremely happy with their new knee, complications can occur and you must be aware of these prior to making a decision. If you are undecided, it is best to wait until you are sure this is the procedure for you.
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