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Partial Knee

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Introduction | The Benefits | The Operation | Going Home
Follow Up Programme

What is a partial (uni compartmental) knee replacement?

Total knee replacement is an excellent surgical option for treatment of advanced arthritis of knee joint to relieve the pain and restore the function. When the arthritis is limited to one part of the knee joint, a partial (uni compartmental) knee replacement is a viable option with its added advantages.

Normal knee joint has three anatomic compartments: Medial compartment-the inside part of the knee, Lateral compartment-the outside part of the knee and Patellofemoral compartment- the front of knee between kneecap (patella) and lower end of thigh bone (femur).

When the knee is affected by the arthritis, all three compartments are generally involved. This is usually treated with a total knee replacement when the symptoms are not satisfactorily controlled with non-operative treatment. However arthritis is sometimes limited to only one compartment of the knee joint and can cause severe pain and stiffness. Under these circumstances a partial replacement (unicompartmental) of the knee is a viable option if the symptoms are not adequately controlled with non-operative treatment.

Am I suitable candidate for a partial (unicompartmental) knee replacement?

This operation is commonly indicated in osteoarthritis of the knee joint. You may be a suitable candidate for a partial (unicompartmental knee replacement) when:

Your arthritis is mainly limited to one compartment of the knee joint
Symptoms are not satisfactorily controlled with non-operative treatment
You are older than 55-60 years
You lead a relatively sedentary lifestyle
You are not overweight
Range of movement in the knee is satisfactory (more than 90 degree flexion)
You do not have severe deformity at the knee joint
Your major ligaments in the knee are normal

Partial (unicompartmental knee replacement) is not suitable if you suffer from rheumatoid arthritis and other inflammatory arthropathies. It is also not routinely indicated if your knees are stiff, severely deformed and ligaments are damaged.

Proper selection of patients is very important for successful outcome after the partial (unicompartmental) knee replacement. Improved surgical techniques combined with modern unicompartmental knee replacement designs have demonstrated excellent 5 to 10 year results after partial knee replacement.

What are the different types of partial (unicompartmental) knee replacement?

There are three types partial knee replacement.

1. Medial compartment knee replacement: This type of partial knee
replacement is performed when the arthritis is limited to the inner side
of the knee joint. This is the most commonly performed type of partial
knee replacement.

2. Lateral compartment knee replacement: This type of knee replacement
is performed when the arthritis is limited to the outer side of knee joint.

3. Patello-femoral joint knee replacement: This type of partial knee replacement
is performed when the arthritis is limited to backside of kneecap (patella) and
the front of lower end of thigh bone (femur).

What are the benefits of partial (unicompartmental) knee replacement?

Current studies demonstrate that modern unicompartmental knee replacements produce excellent results when the patients are selected properly for this procedure. The main benefits of the partial (unicompartmetal) knee replacement over total knee replacement are:

Smaller incision
Less pain after surgery
Quicker recovery
Less blood loss
Shorter recovery period

As the bone, ligaments and cartilage from healthy parts of the knee joint are preserved, majority of the patients with partial (unicomapartmental) knee replacement experience more natural feeling in their knee than with a total knee replacement.

Before partial (unicompartmental) knee replacement operation

Once you have agreed to undergo partial (unicompartmental) knee replacement surgery Mr Samsani may ask for a medical review by a Physician. Medical review is important to stabilise your medical conditions so that you are fit enough for operation and complete rehabilitation. If you suffer from serious and chronic medical problems you may also have to be seen by Specialists such as Cardiologsts, Nephrologists etc. before operation.

You will also:

- Undergo blood and urine tests and an ECG together with chest x-ray in preparation for surgery
- Inform Mr Samsani or his team about all the medications you are currently taking. You may have to stop some medications before surgery and others can be continued.
- Inform Mr Samsani or his team of any drug or metal allergies you may have

Dental infections must be treated and major dental procedures must be completed before operation. Patients who suffer from frequent urinary tract infections must have a urine sample to rule out infection and if present should be treated before surgery.

Your mobility may be slightly restricted for few weeks after operation so you may have to discuss with your family regarding assistance in the early postoperative period.

Some home modifications may be required to help recovery after surgery. A stable high chair with firm seat cushion and side arms is required. A toilet seat riser with arms is also very useful in the postoperative period.

Partial (unicompartmental) knee replacement operation

You will be admitted to hospital one day before or on the day of operation. Before surgery Mr Samsani will see you and confirm the site of operation. He will also put a mark on the knee that is going to be operated. Mr Samsani will also explain to you that if your knee is found to be not suitable for partial knee replacement during surgery, he will instead perform a total knee replacement.

Before your operation an anaesthetist will also come and see you. The anaesthetist will perform a brief medical assessment and discuss the anaesthetic options you can consider for your operation.

The operation usually takes between 1 to 2 hours and is performed either under general anaesthesia or regional anaesthesia. A tourniquet- a tight pressure bandage, is placed around the upper thigh to minimise blood loss from surgery. Tourniquet does not usually cause any problems but may occasionally result in some bruising after the operation for a few days.

An 8 to 10cm incision is made in front of the knee and knee joint is entered. Then the rest of the knee joint is carefully examined to make sure that arthritis is limited to one compartment and ligaments are normal. If Mr Samsani finds that arthritis is present in more than one compartment of the knee joint, he will instead perform a total knee replacement.

If your knee is found to be suitable for partial knee replacement, damaged cartilage is removed with special instruments and the ends of the thigh bone (femur) and shin bone (tibia) are prepared to implant metal components. The metal components are held to the bone with surgical cement. A plastic spacer is then placed between the two metal components to allow smooth movement of knee joint. The wound is then closed with stitches or clips and bulky dressing with wool and crepe bandage is applied.

What happens after the operation?

Immediately after the operation you will be transferred to recovery which is very close to the operation theatre. You will be closely monitored here to prevent or detect any early problems that may occur after operation. When Mr Samsani and his anaesthetist are happy with your recovery, you will then be moved to a ward where the rest of your post-operative recovery will take place until discharge from the hospital. Sometimes patients with complex medical problems may be transferred to a high dependence ward (HDU) or intensive care unit (ICU) for intense monitoring before moving back to the ward.

You will have the following in the recovery or early postoperative period;

- Intra-venous drip attached to a vein of the arm to give fluids, medications and sometimes blood transfusion.
- A blood pressure cuff around the arm to measure blood pressure regularly.
- A pulse-oximetre attached to your toe or finger to measure pulse rate and oxygen levels in the blood.
- A bulky wool and bandage dressing wrapped around the operated knee to cover the wound.
- Sometimes a drain tube is attached to drain excessive blood from the knee wound. This will be removed in 24 to 48 hours later in ward.
- IV antibiotics are administered to minimise the risk of wound infection
- Injections or oral medicine are given to reduce the risk of blood clot formation.

Patient is allowed to drink and eat as soon as they feel better. Patient is generally encouraged to drink plenty of fluids to prevent dehydration and also to flush out the anaesthetic medicines from the body. Nausea and vomiting can occur after the operation which usually settles down with time but sometimes medicines are given to control these symptoms. You may sometimes require blood transfusion due to blood loss as result of operation. You will also have a blood test to make sure your haemoglobin is with in satisfactory range and have an x-ray of the operated knee to document position and alignment of the prosthesis.

Pain relief after the partial (unicompartmental) knee replacement

Partial (unicompartmental) knee replacement is a major operation and some amount of discomfort is common after the operation. The pain is usually controlled with pain killers given either through a vein or through mouth or combination of both. Pain killers are taken at regular intervals to prevent any breakthrough pain in the initial days and after that they are usually taken on demand (when the pain is felt). Adequate postoperative pain relief is also essential to commence early mobilisation and physiotherapy. If you experience any discomfort or pain please ask the help of the nurses on the ward for immediate pain relief.

Physiotherapy after partial (unicompartmental) knee replacement

After the operation, a physiotherapist will visit you on the ward in
24 to 48 hours. Physiotherapist will teach you how to use the
artificial knee and advise you about various exercises you need to
do after partial knee replacement operation. It is very important to
start the exercises early and regularly after the operation to facilitate
quick recovery. Range of movement exercises are necessary to
improve flexion and extension of the knee joint, and quadriceps
strengthening exercises are very important for strengthening of thigh
muscles. Generally a range of movement from 0 to 120 degrees of
flexion can be expected after partial knee replacement. It is important
to remember that the final range of movement that can be achieved
after operation is mainly determined by the pre-operative range of
movement in the knee joint.

Going home after partial (unicompartmental) knee replacement

You will be able to go home after partial (unicompartmental) knee replacement when:

- You are walking safely with the help of crutches
- When the knee wound is satisfactory.
- Pain is adequately controlled with oral pain killers
- You are able to eat and drink well
- You do not have any other medical complications

Successful outcome following the partial (unicompartmental) knee replacement depends on how well you follow the instructions given by Mr Samsani and his physiotherapy team. Some amount of pain or discomfort is expected especially in the first few weeks after operation and should be able to adequately control with pain killers.

Wound care: Ensure that wound is dry until it is completely healed. You will have stitches or staples running along the wound and these stitches or staples will be removed in few weeks after surgery. You can have a shower once the wound is completely healed and dry. Some amount of swelling and bruising of knee is common and can take up to few months for complete improvement.

Diet: You should try and eat well after the operation. Also you should also drink at least 3 or more litres of water or other soft drinks to prevent dehydration and to flush out various drugs from your system. A balanced diet with iron supplementation, high fibre foods, salads and fruits is important to help the wound heal quickly and to restore muscle strength.

Activity: your normal activities are gradually restored and continuing with exercises at home is very important for quicker functional recovery. Most activities of the daily living will be resumed in 6 to 8 weeks after partial (unicompartmental) knee replacement. Some pain or discomfort after activity and sometimes at night is common for 3 to 4 weeks after total knee replacement. Your home activity programme includes;

- A progressive walking programme to increase your walking ability with or without the help of walking aids.

- Gradual return to normal day to day activities such as sitting, standing and climbing stairs.

- Specific exercises to strengthen leg muscles and improve range of movement at knee. These exercises should be performed several times a day and should be continued for several months until optimum strength and movement are restored.

- Driving can be resumed when your knee has achieved sufficient bend to enter and come out of car comfortably and when you have adequate muscle control in the leg for breaking and acceleration. Majority of patients resume driving at 6 to 8 weeks after surgery.

Possible risks of partial (unicompartmental) knee replacement

Partial (unicompartmental) knee replacement is a very successful operation in carefully selected patients. A general or regional (spinal or epidural) anaesthesia or combination of these techniques is required to perform the operation. A small risk of complications is associated with administration of any these anaesthetic techniques. Before the operation an anaesthetist will come and see you and explain the pros and cons of each anaesthetic technique.
Mr Samsani will also explain and discuss with you (at the time of out-patient consultation as well as before operation) in detail about the possible risks of the surgery and approximate rehabilitation time.

Anaesthetic Risks

There is always a small risk associated with administration of general or regional (spinal or epidural) anaesthesia. Major medical complications such as heart attacks, strokes or chest infection are less common. The risk is increased if the patient is older and has multiple medical conditions which may have affected the functions of vital organs such as heart, lung, liver and kidneys. A pre anaesthetic assessment will be carried out before surgery to optimise medical condition and minimise the risks associated with anaesthesia and surgery.

Partial (unicompartmental) knee replacement surgery risks:

Major bleeding: Very rare and blood transfusion(s) may be required when this happens.

Infection: Incidence of infection after partial knee replacement is very rare. The risk of infection is reduced by administration of prophylactic antibiotics in the perioperative period. Infection may occur in the hospital or after you go home. Superficial infections are usually treated with antibiotics and the deep infections may require washout of the wound in addition to administration of antibiotics. Rarely the deep infection may not respond to the antibiotics alone and may require implant removal and reinsertion of implant after some time as a two stage procedure. If you experience any signs of infection in the operated knee such as swelling, redness, excessive pain or discharge from wound, you must contact Mr Samsani’s team for immediate assessment and treatment.

Deep Venous Thrombosis and Pulmonary Embolism: Blood clots can occur after any type of knee surgery including partial knee replacement. This risk is reduced by administration of blood thinning Injections or tablets after surgery. Other measures such as elevation of legs, TED stockings and calf compression devises are also used to reduce the risk of blood clots. Exercises and early mobilisation after surgery also reduces this risk. Rarely, if not detected and treated properly, a portion of the blood clot can break off and migrate to lungs causing pulmonary embolism, a serious and life threatening condition.
Stiffness: Occasionally stiffness of the knee joint can occur after following partial knee replacement particularly in patients who are overweight or have diabetes. In majority of cases the stiffness improves with physiotherapy and exercise and rarely may require manipulation under anaesthesia to reduce the stiffness.

Reflex sympathetic dystrophy: It is also called as “complex regional pain syndrome”, a rare condition in which the knee can become painful, stiff and hypersensitive after surgery. Majority of cases respond to non-operative measures and may require specific treatment from a pain specialist.

Fracture of knee: fracture of upper end of shin bone can occur during the surgery but is very rare. The fractures that occur during surgery are usually treated immediately with wiring or plating. It is very rare to see these fractures after the surgery unless you have been involved in a bad accident.

Loosening of prosthesis: Majority of artificial knees may not last forever. They can wear out or become loose during an individual’s life time. If the prosthesis becomes loose it may require revision.

Damage to nerves and vessels: Damage to major nerves (tibial and peroneal nerves) around the knee joint is very rare. However it is very common to have an area of numbness over the outside of your knee where a superficial skin nerve is always cut to perform surgery. This numbness will not affect functional outcome after operation.

Scarring: Scar tends to be thicker in some patients than others and usually does not cause any major problem.

How is my partial knee replacement different from my own knee joint?

It is very important to understand that the primary aim of the partial knee replacement operation is to improve the quality of life by relieving pain and improving function in the knee. Movement in the knee will improve but may not be fully restored after total knee replacement operation. Movement in the knee after partial knee replacement is mainly determined by the range of movement you have in the knee before the operation.

Kneeling can cause discomfort due to pressure on the scar but is not generally harmful.

Numbness around the scar especially on the outside of the knee is very common after operation. This numbness does not affect the functional outcome after operation.
Majority of patients also experience clicks or clunks in the artificial knee due to the metal and plastic components in the knee during bending of knee or walking. This is normal and again does not affect the functional outcome of your new knee. These clicks or clunks usually disappear with time.

Your new knee may activate metal detectors at airports or other security places. Inform the security officer that you have an artificial knee.

How to avoid problems after partial knee replacement?

Preventing infection: Infection after partial knee replacement is rare. However presence of an active focus of infection in the body can spread the bacteria through the blood steam. These bacteria then can lodge around the partial knee and result in infection. Common causes of such infection are urinary tract infections and skin and nail bed infections and must be treated with antibiotics immediately. You must also take prophylactic antibiotics too before any dental procedure to prevent spread of bacteria through the blood stream.

You must contact Mr Samsani or his team immediately if you develop any of the following signs of possible infection in the partial knee replacement:

- High fever
- Chills
- Redness, swelling and tenderness of knee wound.
- Discharge from knee wound
- Severe pain in the knee at rest or at night.

Prevention of Blood clot: Blood clots can occur in the legs after knee replacement. Early mobilisation and continuation of exercises after operation combined with administration of blood thinning medication reduces the risk of blood clots in legs.
You must contact Mr Samsani or his team immediately if you develop any of the following signs of possible blood clots in your legs:

- Increasing pain in your calf
- Increasing swelling in your calf, foot and ankle.
- Tenderness in the calf

Very rarely the blood clot can dislodge from legs and migrate to lungs resulting pulmonary embolism. The following are warning signs of pulmonary embolism:

- Sudden onset of chest pain
- Sudden onset of breathlessness>
- Cough with chest pain

You must go to the Emergency Department or see the nearest qualified doctor immediately to treat this life threatening condition.

Preventing falls: For a few weeks after the operation, due to pain stiffness and lack of strength in leg muscles, your gait may be little unsteady and falls may occur. Stairs and uneven surfaces are particularly hazardous. Falls immediately after operation can cause serious damage to your new knee and may result in need for further surgery. Therefore you should use a walking stick, crutches, frame or have someone to help you until your balance, flexibility and strength is improved.

How can I protect and prolong the life of my partial knee replacement prosthesis?

- Continue with regular light exercise programme to maintain the strength in the muscles of leg and mobility in the partial knee replacement
- Avoid falls
- Take prophylactic antibiotics before any dental procedures
- Regular follow up examinations as advised by Mr Samsani or his team
- Try and avoid putting excessive weight to reduce stress on the artificial joint

Follow up programme after partial (unicompartmental) knee replacement

After partial knee replacement it is important to review patients at regular intervals to make sure the artificial joints are functioning well and also to detect any problems early. You will normally be reviewed at the following dates after partial knee replacement:

6 to 8 weeks after surgery: clinical review
6 months after surgery: clinical review and questionnaire
12 months after surgery: clinical review, x-ray and questionnaire
Then every 2 years...