Information about

Total Knee Replacement

Introduction

Total Knee Replacement (TKR), also called Total Knee Arthroplasty (TKA), was first performed in 1968. Since then, there have been several innovative improvisations in implant design and surgical techniques, most notable being computer navigation. Total Knee Replacement has revolutionized the treatment of severe knee arthritis. The first Total Knee Replacement in India was performed in 1976 at Bombay Hospital (Mumbai) by Dr Chitranjan Ranawat and Dr K T Dholakia. Today, TKR is routinely performed in various super-specialty centers in India at Mumbai, Pune, Chennai, Ahmedabad and New Delhi. Let us briefly study the anatomy of the knee joint before understanding the basic concepts of knee replacement.

Anatomy of the Knee Joint

The knee joint is formed by three bones – femur (thigh bone), tibia (shin bone) and the patella (kneecap). The joint works like a hinge, but it also has some rotational and gliding movement. Thus, the knee is a modified hinge joint. The femur connects separately with the tibia and the patella. The patella is attached to the tibia through the patellar tendon. The knee joint is stabilised internally by the anterior and the posterior cruciate ligaments (ACL and PCL); and externally by the medial and the lateral collateral ligaments (MCL and LCL). In addition, the knee contains two semilunar cartilages, the medial meniscus and the lateral meniscus, which change the contour of the end of the femur, thus facilitating better load trasfer across the joint.The ends of the bones which come in contact with each other are covered with articular cartilage, which acts as a shock-absorber.

With advancing age there is wear and tear in the knee, and degnerative changes of osteoarthritis (OA) are seen. Initially, the cartilage gets worn off. Later, bone gets rubbed against bone (femur against tibia and femur against patella), with further knee joint damage. Alignment of the knee also gets disturbed, leading to deformity in the leg. Arthritic changes are seen in varying proportions in the three compartments of the knee (medial, lateral and patello-femoral).

Similar changes occur in rheumatoid arthritis (RA), which is seen at any age, including early adulthood

Basics of TKR

The knee joint is formed by three bones – femur (thigh bone), tibia (shin bone) and the patella (kneecap). The joint works like a hinge, but it also has some rotational and gliding movement. Thus, the knee is a modified hinge joint. The femur connects separately with the tibia and the patella. The patella is attached to the tibia through the patellar tendon. The knee joint is stabilised internally by the anterior and the posterior cruciate ligaments (ACL and PCL); and externally by the medial and the lateral collateral ligaments (MCL and LCL). In addition, the knee contains two semilunar cartilages, the medial meniscus and the lateral meniscus, which change the contour of the end of the femur, thus facilitating better load trasfer across the joint.The ends of the bones which come in contact with each other are covered with articular cartilage, which acts as a shock-absorber.

There are several technical considerations in TKR surgery, such as a posterior-stabilized (PS) vs a cruciate-retaining (CR) knee; fixed bearing vs rotating platform; and cemented vs uncemented components. These issues are dealt with according to surgeon preference and the patient’s needs. All of these procedures have extremely good results.

Another important consideration is the use of computer navigation in knee replacement. There are several studies which indicate that computer – assisted surgery (CAS) improves the accuracy of alignment in TKR. For further details about CAS, click here.

A newer modality is Patient-Matched Instrumentation (also called Patient Specific Instrumentation or PSI), which is a modification of CAS.

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Revision TKR

TKR has to be re-done or revised after the primary implant wears out. This happens after about 20 years. But it can occur even earlier if the original implant is not placed in perfect alignment, or if the soft tissues around the knee are not balanced (i.e. loose on one side and tight on the other). Also, a well-done primary TKR may need to be revised early if the patient does not take proper care and indulges in excessive physical activities. Infection also sometimes necessitates the removal and staged revision of the knee.

In revision TKR, the original components are carefully removed, taking care not to fracture the bones. The bone cement is also excised completely. Care is taken to avoid removing part of the good bone. After confirming that there is no infection, new specially designed components are implanted. These typically have long stems that go into the femur and tibia. The polyethylene insert has a greater degree of ‘constraint’, thus imparting more stability. The revision components have the provision of metal wedges being added to them to compensate for any bone loss. The revison TKR implants also come in the configuration of a ‘hinge’.

With proper care and surgical experience, the results of revision TKR are very good. Re-revison is also possible.

Who needs total knee replacement surgery?

You may need knee replacement surgery in the following situations:

  • You suffer from severe knee pain during daily activities like walking, sitting cross-legged, climbing or descending stairs, or getting up from a sitting position
  • Pain in the knee is present while at rest or at night
  • Your ability to bend your knee is restricted and the knee becomes stiff
  • Pain-killers are required almost daily and are effective only for a short duration
  • Weight-reduction, physiotherapy and lifestyle modification are not helpful in getting rid of knee pain

Risks and Benefits of Total Knee Replacement Surgery

The patient has to be convinced that he or she needs a TKR surgery, and that no other option is going to help (see section: Who needs total knee replacement surgery). Before deciding about the surgery, the patient must be aware of the benefits and the potential risks of TKR surgery.

Benefits of Total Knee Replacement

  • The most important benefit of TKR is complete pain relief.
  • Near-normal range of motion in the knee (bending upto 1350) is possible, which means that the patient will be able to perform all of his or her daily activities easily.
  • Walking for about 2 km, climbing up or descending stairs, swimming, driving a car and all daily activities at home or work are possible with no pain.
  • Light sports such as golf, table-tennis or badminton are allowed after TKR, but not jogging and football.

Risks of Total Knee Replacement

1. Infection in the wound – This is a serious problem, but fortunately it is extremely rare. The most common cause of infection is a focus of infection in the body (like an infected tooth or skin lesion or urinary tract).

All surgeons take stringent care to prevent infection after a TKR surgery.

The operation theatre is spacious, and is equipped with a modern laminar air-flow system for ensuring clean air.

Disposable body-exhaust suits (colloquially called space-suits) are used by the surgeon and his team to minimise infection. Utmost aseptic precautions are taken before, during and after the surgery.

Antibiotics are used perioperatively to minimise any chance of infection.

The risk of infection is low (less than 1%), but it cannot be ignored.

2. Venous Thromboembolism or VTE – This means formation of blood clots in the leg veins of the patient, which sometimes migrate to the heart and lungs. This problem is prevented by giving blood-thinner medications for a few days after the surgery, and by doing exercises to maintain blood circulation in the leg in the post-operative period.

3. Complications due to medical problems like heart disease, hypertension, diabetes, allergies and asthma can occur, but with modern medical care, this risk is also very low.

4. Extremely rare complications are

  • Injury to tendons,ligaments, nerves and blood vessels near the area of operation – this risk is almost negligible.
  • Fractures of bones during the operation – this sometimes occurs in severely osteoporotic patients or in rheumatoid arthritis, when the bones are extremely weak.

Preparation for surgery

After you decide that you are going ahead with the operation, you will have a complete medical examination before your surgery. This is required to detect any problems which may adversely affect your recovery. Any abnormalities such as high blood pressure, low haemoglobin, diabetes, heart disease or asthma are managed with medicines in the appropriate manner. Smoking should be stopped 3 – 4 weeks before the surgery.

Investigations: Blood tests, Urine examination, Chest X-ray, ECG and 2D Echo are done in every patient, though a few patients may require further tests.

Skin care: Skin lesions are treated completely to prevent cutaneous infection spreading to the knee joint after surgery.

Dental care: Dental procedures like tooth extractions and root canal treatment may lead to bacterial contamination of the bloodstream. Therefore, such procedures should be done well before a TKR surgery.

Urinary evaluation : Urinary tract infection can similarly spread (through the bloodstream) to the knee joint after TKR. Hence, it has to be treated adequately. A urine test will usually detect any urinary tract infection.

Chest evaluation: Chest infection (upper or lower respiratory tract infection – URTI or LRTI) can also spread through the bloodstream to the knee joint after TKR. Therefore, if present, it has to be treated completely.

X-Ray Templating

Your X-Rays will be carefully studied by your surgeon in order to do a pre-operative planning. Transparent films with the prosthesis outline (called templates) are superimposed on the X-Rays. Also, the bone cuts are marked on the X-Ray films. Special full-length X-Rays called scanograms may sometimes be required.

The actual procedure (TKR)

You will be admitted to the hospital one day before the operation. You must bring all the investigation reports and X-Rays with you. After admission, you will be examined by your surgeon and a member of the anaesthesia team. Usually, you would require overnight starvation if the surgery is scheduled for the next morning.

Anaesthesia:

In most cases, you will be administered spinal anaesthesia (SA), which keeps you awake during the operation but anesthetizes the lower half of your body. This is sometimes coupled with an epidural (EA). But in some cases, you will be given general anaesthesia (GA). The anaesthesia team will decide which type of anaesthesia is appropriate for you.

Surgical Procedure:

The surgery lasts for about one and a half hours (two hours if CAS is used). However, it can take longer in a few patients. In addition, about one hour is needed for preparation and anaesthesia induction before the actual surgery, so that the patient may be in the operation theatre for almost 4 hours. The following pictures demonstrate the steps in a conventional total knee replacement surgery.

(A) Femoral Preparation:

(B) Tibial Preparation:

(C) Patellar Preparation:

(D) Extension Gap, Flexion Gap, Gap Balancing and Patellar Tracking:

Once the prosthesis is implanted, the knee is checked for stability and full range of motion.

Recovery Room / ICU:

Post-operative X-Ray after Total Knee Replacement

After surgery, you will be transferred to the recovery room for about two hours till you fully recover from anaesthesia. After you awaken fully, you will be shifted to your hospital room. In a few cases you may be moved into an ICU for 24 hours for additional safety. Post-operative X-Rays are done at this stage.

The actual procedure (TKR)

When you are still in the hospital

You will be hospitalized for about 4 to 5 days. After surgery, there will be some pain in the knee. You must be prepared for this. The pain is no different and no more than any other surgical procedure, and usually lasts for 2 -3 days. Round-the-clock pain medications will be given to make you comfortable.

Antibiotics and blood-thinners will be given as required.

You will be made to stand and walk 24 – 48 hours after your surgery, with the aid of a walker. Your surgeon and the physiotherapist will supervise your exercise program in the hospital.

After discharge from the hospital

After discharge, you will be taking care of yourself with the help of relatives. Your surgeon and the physiotherapist are just a phone call away, and will be ready to assist you in any way if needed. But you have to be sure that you have understood the doctor’s instructions at the time of discharge from the hospital, as the success of your operation will be largely dependent on how well you follow these instructions.

Diet :

A balanced diet rich in iron, calcium and mineral supplement is advised. Good fluid and water intake is required. Some patients have constipation for 2 – 3 days, and some may have anorexia (loss of appetite) for a few days after surgery.


Wound Care:

The operative wound is closed with stitches or staples, which will be removed after two weeks. Till then, the wound should not get wet, and the dressing must remain intact. After suture / staple removal, the surgical area can be bathed normally, as the wound is healed by then.

Medications:

You will need antibiotics and pain-killers for a few days after surgery. Also, you may need specific medication for diabetes, heart disease and hypertension. Blood-thinners are also required for the prescribed period to prevent blood clots (venous thromboembolism).

Activities and exercise:

You must carefully follow all instructions from your surgeon and your physiotherapist regarding the exercise program after the surgery. Physiotherapy is important to maintain muscle strength, joint mobility, and to prevent complications like venous thromboembolism. The physiotherapist will train you how to walk with a walker. He or she will instruct you regarding how to attend to your personal hygiene. Later, you will be asked to climb up and down the stairs. Gradually, you will switch over from your walker to a walking stick, and then to independent ambulation.

Precautions after surgery

  • In order to avoid putting excessive loads on the new implant in your body,
    • do not squat or sit cross-legged on the floor
    • do not use Indian-style toilet
    • do not play impact sports like football or jogging
  • Prevention of blood clots in the leg veins – Blood clot formation will be prevented with an exercise program and blood-thinner medications. However, you have to be alert as to any tell-tale warning signs about blood clots, and inform the doctors and nurses immediately. Warning signs of possible blood clots are: pain, tenderness, swelling or redness in the calf and leg. If the blood clot has migrated to the lung, there may be difficulty in breathing or chest pain.
  • Prevention of post-operative infection – Antibiotics will be administered to prevent infection. However, if infection does occur, it is relatively easy to treat if it is detected early. Warning signs of a possible infection in the knee after a TKR surgery are: redness, tenderness, swelling of the knee wound or persistent fever (> 1000 F).