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Total Knee Replacement

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Total Knee Replacement (TKR)

A Total Knee Replacement (TKR) or Total Knee Arthroplasty is a surgery that replaces the worn surfaces of an arthritic knee joint with artificial metal and plastic replacement parts.

The procedure is usually recommended for older patients who suffer from pain and loss of function from arthritis and have who have failed to achieve satisfactory relief from other more conservative methods of therapy. Age by itself if no barrier to TKR. TKR can be done in younger adults if the symptoms are severe enough and no other effective medical or surgical treatment option exists.

A typical knee replacement replaces the ends of the femur (thigh bone) and the tibia (shin bone) with metal. A plastic bearing is inserted between them and on the back of the patella (knee cap).

Fig 1. Severe deforming knee osteoarthritis. Fig 2. TKR. Frontal projection. Fig 3. TKR. Side projection.

Arthritis

Other causes include:

  • Trauma (fracture).
  • Increased stress e.g., overuse, overweight, etc.
  • Infection.
  • Connective tissue disorders.
  • Inactive lifestyle e.g., Obesity, as additional weight puts extra force through your joints which can lead to arthritis over a period of time.
  • Inflammation e.g., Rheumatoid arthritis.

In arthritis, the cartilage lining on the ends of the bones is thinner than normal or completely absent. The degree of cartilage damage and inflammation varies with the type and stage of arthritis.  The capsule of the arthritic knee is thickened.  The joint space is narrowed and irregular in outline; this can be seen in an Xray image.  Bone spurs or excessive bone can also build up around the edges of the joint.  The combinations of these factors make the arthritic knee stiff and limit activities due to pain or fatigue.

Diagnosis

The diagnosis of osteoarthritis is made on history, physical examination & Xrays. There is no blood test to diagnose Osteoarthritis (wear & tear arthritis).

Benefits of TKR

The decision to proceed with TKR surgery is a cooperative one between you, your surgeon, family and your local doctor.

The benefits following surgery are relief of symptoms of arthritis. These include:

  • Severe pain that limits your everyday activities including walking, shopping, visiting friends, getting in and out of chair, gardening, etc.

  • Pain waking you at night.

  • Deformity- either bowleg or knock knees.

  • Stiffness.

Prior to surgery you will usually have tried some conservative treatments such as simple analgesics, weight loss, anti-inflammatory medications, modification of your activities, canes, or physical therapy. Once these have failed it is time to consider surgery. Most patients who have TKR are between 60 to 80 years, but each patient is assessed individually and patients as young as 20 or old as 90 are occasionally operated on with good results.

Pre-Operation

TKR is a major procedure that should be undertaken under optimal conditions. This means that your general health needs to be assessed and any correctable problems dealt with prior to surgery. In most circumstances this will involve blood tests, an ECG and an echocardiogram. Ideally this should be done by your GP prior to you being referred for major surgery. This is especially important if you have a known heart condition and have not been seen by your cardiologist in the recent past. Dr McEwen will organize much of the appropriate testing to be conducted prior to your consultation if not already done. This is very important to minimize surgical risk to yourself. Take note of the following:

  • High Blood Pressure (Hypertension) should be controlled and stable.

  • Diabetes should be controlled and stable with blood sugar levels checked regularly.

  • Any cardiac symptoms (chest pains, shortness of breath, palpitations) should be investigated and treated.

  • Sleep apnoea should be investigated and treated.

  • BMI should be less than 35. BMI is a measure of obesity and is calculated by dividing weight in kg by the square of height in meters. For example someone who weighs 100kg and is 1.89m tall will have a BMI 100/1.89x1.89 = 100/3.57 = 28. The normal range for a BMI is 20-25. A BMI over 35 is associated with an increased risk of serious complications and Dr McEwen will apply this as a cutoff for TKR. If your BMI is over 35 you should lose weight before seeking a TKR. This should be done with the aid of a dietitian and exercise physiologist.

  • Smoking is very dangerous when combined with major surgery. Smoking must be ceased. Dr McEwen will not undertake a TKR if you're smoking.

Many medications have an effect on bleeding, blood clotting and wound healing. Blood thinning medications (Aspirin, Clopidogrel, Warfarin, Pradaxa) will need to be ceased at least 5 days prior to surgery. Dr McEwen will give specific instructions regarding this. Seek clarification well before surgery if unsure.

Cease any naturopathic or herbal medications 10 days before surgery.

Look after your skin. The skin on the leg being operated on must be free of cuts, scratches, grazes and bites.

Day of Your Surgery

You will be admitted to the hospital either the evening before or on the day of your surgery depending on the time your surgery is scheduled for.
Blood tests may be required on admission.
You will meet the nurses and answer some questions for the hospital records.
You will meet your Anaesthetist, who will ask you a few questions.
You will be given hospital clothes to change into and have a shower prior to surgery.
The operation site will be shaved and cleaned.
Approximately 30 minutes prior to surgery you will be transferred to the operating theatre complex.

Surgical Procedure

Surgery is performed under sterile conditions in the operating room under spinal or general anaesthesia. You will be positioned on your back and a tourniquet applied to your upper thigh but used for only a brief period to reduce injury to the thigh muscles. The surgery takes approximately two hours.

For a TKR to work well the prosthetic knee must mimic the patient’s pre arthritic knee as closely as possible. This means that the sizing, positioning and alignment of the TKR need to be matched to each patient’s anatomy. Sizing, positioning and aligning can be done in 3 ways:

  1. Conventional Instrumentation (Old School). Mechanical jigs are used around or through the centres of the femur and tibia. Cutting blocks are mounted on these jigs and the worn ends of the bones removed by cutting through these blocks.

  2. Computer Assisted Surgery (The Gold Standard). Position sensors are attached to the bones and used to teach a computer about the specific anatomy of the knee in a process called registration. A customized plan is developed to achieve optimal sizing, positioning and alignment. This plan is then executed using the computer to position the cutting blocks and to check that each step has been completed as per the plan. Used to its full extent Computer Assisted Surgery is a very powerful tool that predictably leads to better sizing, positioning and alignment compared to conventional instruments.

  3. Shapematching (Patient Specific Instruments). Cutting blocks are manufactured based on a preoperative CT or MRI scan of the knee. Shapematching is a unique type of patient specific instrumentation that is MRI based and works by identifying the pre-arthritic centre of rotation of the patient’s knee on the planning MRI. Cutting blocks are then manufactured and used to position the TKR at the same centre of rotation as the prearthritic knee. Shapematching can produce a very close match between the pre-arthritic knee and the replaced knee and therefore, hopefully, a knee replacement that feels and moves more like a normal knee. Shapematching is a new technology that at this point in time is not applicable to all situations.

Dr McEwen uses Computer Assisted Surgery or Shapematching for all TKRs.

Accurate sizing, positioning and alignment make a successful TKR a possibility but constitute only one part of the formula for success. The remainder of the formula is ensuring that pain and swelling don’t get in the way of movement. Many things contribute to this including:

  1. Spinal anaesthesia. A spinal anaesthetic lasts for 4-7 hours, is usually combined with a light general anaesthetic and has several advantages:

    1.  It allows the patient to wake without pain and time for secondary pain relief measures to kick in before the limb becomes sensate again.

    2. It dramatically reduces the amount of anaesthetic medicine used so problems like nausea, vomiting, drowsiness and disorientation are much less likely to occur.

    3. It allows the anaesthetist to the keep the blood pressure low and even so there is no need to use a tourniquet for long periods (see below).

  2. Limiting Tourniquet Time. A tourniquet prevents blood loss during the operation but causes pain, swelling and wasting of the thigh muscles. If the blood pressure is kept low and even a tourniquet is used for short periods only or not at all without increasing blood loss. Pain is reduced and control of the knee by the thigh muscles is better and recovers faster.

  3. Muscle Sparing Approach. There are several ways to surgically enter the knee. Each has its pros and cons. Muscle sparing approaches do less damage to the quadriceps so control of the knee is better and recovers faster.

  4. Periarticular Injection. The lining of the joint (synovium) is very sensitive and is the source of much of the pain, swelling and scarring after TKR. A periarticular injection of painkillers and anti-inflammatory drugs into the synovium and other tissues around the knee during the TKR reduces pain, swelling and scarring and is particularly effective when combined with a spinal anaesthetic and a cryocuff.

  5. Cryocuff. A cryocuff is a mobile, patient operated ice delivery system that reduces pain and swelling. The cryocuff is applied to the knee after wound closure and will be operational long before the spinal anaesthetic wears off.

  6. Multimodal Analgesia. A combination of drugs are used to manage pain and ensure reasonable sleep after the TKR.

Dr McEwen employs all these strategies routinely. All TKR patients will discharge with a cryocuff which is returned after 2 weeks. The vast majority of TKR patients will walk the day of surgery and walk out of hospital within 24-72 hours. This does not mean that there will be no pain or swelling but that pain will be manageable and much less likely to interfere with movement.

Bilateral TKR. Knee osteoarthritis frequently affects both knees. Having both knees replaced at the same time has many advantages but is not applicable to all situations. The vast majority of patients having both knees replaced will walk the day of surgery and walk out of hospital within 4-5 days.

Post-Operative

Getting over major surgery without any problems requires an active approach to prevent problems rather than reacting to problems once they occur. The rule with prevention is “the sooner the better”. Therefore there are a few things the patient should actively take responsibility for:

  1. Ice therapy. Turn over the water in the cryocuff at least hourly unless sleeping.

  2. Triflo. Use your incentive spirometer as soon as possible. 10 good hard efforts every hour. This prevents pneumonia.

  3. Blood Clot Prevention. Drink plenty of fluids. Do calf pump exercises when lying or sitting. Be prepared to be out of bed a few hours after surgery. Being up quickly is the most important.

  4. Pain Control. Don’t let pain ramp up. As soon as you are aware that pain is increasing let the nursing staff know. Much less painkiller is required to keep pain away compared to beating severe pain into submission.

The nursing staff will assist you with these issues but remember to actively take control of your own well-being.

Physiotherapy begins the day of surgery and will be a daily event until discharge. The aim is to have you independently mobile and self caring as quickly as possible. Canadian crutches are used for balance, not to take weight as immediate full weightbearing is the goal. Elderly patients tend to be better with a walking frame for balance.

The criteria for discharge are a dry wound, good pain control with oral medications, no high temperatures and a pass mark from the physiotherapist including on stairs. Most will achieve this within 48 hours. Make sure you have your discharge envelope with scripts, information sheets and appointment card when you leave. These information sheets are important and should be read. They are available on this website as well. Hit the Patient Info tab on the home screen and click on Patient Information Pamphlets.

Remember that swelling is the enemy of movement. Use the cryocuff and keep the leg up. Lots of small walks around the house followed by periods of elevation and ice is the correct approach.

Sleep in whatever position is most comfortable. There is no need to sleep only on your back with the knee straight.

The wound should be clean and dry. Notify Dr McEwen immediately if this is not the case.

You will have a postoperative appointment scheduled for 2 weeks after the surgery. Sutures will be removed at this time. Paul Parker, a very senior and experienced musculoskeletal physiotherapist will see you at the same time so leave plenty of time for this. There is no need for supervised physiotherapy between discharge from hospital and your appointment with Paul.

Sleep disturbance is very common after TKR and tends to persist long after walking is easy. Sleep in whatever position is most comfortable, use ice, and use the provided sleeping tablets and painkillers if needed (as long as they are causing no side effects).

Risks and Complications

As with any major surgery, there are potential risks involved. The decision to proceed with the surgery is made because 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. Complications include:

  • Allergic reactions to medications.
  • Blood loss requiring transfusion with its low risk of disease transmission.
  • Heart attacks, strokes, kidney failure, pneumonia, bladder infections Complications from nerve blocks such as infection or nerve damage.
  • Serious medical problems can lead to ongoing health concerns, prolonged hospitalization or rarely death.

Local Complications

  • Infection. Infection can occur with any operation. In the knee this can be superficial or deep. Superficial infections are treated with antibiotics. Deep infections always require surgical treatment as well as antibiotics. Deep infection is an uncommon but very serious complication and many measures are employed during the course of having a TKR to prevent it. In most cases of deep infection the joint can be salvaged but in certain circumstances the TKR will need to be removed and another implanted after the infection is cured.
  • Blood Clots (Deep Venous Thrombosis).These can form in the calf muscles and can travel to the lung (Pulmonary embolism). 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. As with infection, many measures are employed to prevent this complication. These include compression stockings, calf compressors, IV fluids, blood thinning medications but by far the most important is early mobility.
  • Stiffness in the Knee (Arthrofibrosis). As discussed above implant positioning and control of pain and swelling are important if the TKR is to bend well. Other factors including how well the knee bent before surgery and diligent attention to physiotherapy and home exercise are also important. If there is poor progression of movement of the TKR in the first 4-8 weeks after surgery a manipulation under anaesthesia may be required to break down scar forming in the joint.
  • Neurovascular injury (Damage to nerves and blood vessels). All the major nerves and vessels that pass the knee are within a centimetre of the surgical envelope of a TKR. Great care is taken to avoid damage to these important structures. The Common Peroneal Nerve (CPN) is the most commonly but rarely injured but even this occurs rarely. Injury to the CPN (usually caused by swelling rather than direct injury) causes a foot drop. In most cases this recovers spontaneously over a period of weeks / months.
  • Wear. The plastic liner eventually can wear out over time. Improvements in the mechanical properties of the plastic have extended the useful lifespan of a TKR and in most circumstances it is likely that the implant will function beyond 20 years.
  • Numbness. The skin on the outside edge of the incision will be numb after the surgery. Most people are very aware of this in the first 6 months after surgery. The sensation of numbness fades with time but probably never returns absolutely to normal.

Cosmesis

Very commonly severe knee arthritis is associated with changes in the shape and length of the limb. Both are corrected at the time of a TKR. If both knees are deformed and only one is corrected there will be noticeable asymmetry of limb shape and length. This persists only until the other knee is replaced and is not an issue at all if both knees are replaced at the same time.

Summary

Surgery is not a pleasant prospect for anyone, but for some people with arthritis, it could mean the difference between leading a normal life or putting up with a debilitating condition. Surgery can be regarded as part of your treatment plan—it may help to restore function to your damaged joints as well as relieve pain.

TKR is one of the most successful operations available today. It is an excellent procedure to improve the quality of life, take away pain and improve function. In general 90-95% of knee replacements survive 15 years, depending on age and activity level.

Surgery is only offered once non-operative treatment has failed. It is an important decision to make and ultimately it is an informed decision between you, your surgeon, family and medical practitioner.

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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