Total Knee Replacement Surgery

What is a total knee replacement?

A total knee replacement is a surgical procedure where the diseased knee joint bone and cartilage is replaced with artificial material. The knee joint is formed by the lower end of the femur (thigh bone) and the upper end of the tibia (lower leg bone). During a total knee replacement, the end of the femur bone is removed and replaced with a metal cap (bone cement is used to hold the metal cap in place).

The end of the lower leg bone (tibia) is also removed and replaced with a tibial tray (bone cement is used to hold the metal tibial tray in place). A plastic (highly crossed-linked polyethylene - HCLPE) component is clipped onto the tibial tray and will serve as an articulating surface between the femoral metal cap and the tibial tray. If the patella (knee cap) cartilage is also significantly damaged a plastic button (HCLPE) is used to replace the diseased cartilage.

What patients should consider a total knee replacement?

Total knee replacement surgery is considered for patients whose knee joint cartilage and bone have been damaged by osteoarthritis.
Osteoarthritis of the knee may be caused by advanced age (wear and tear) or some patients may have a genetic predisposition to osteoarthritis. This is called primary osteoarthritis.

Osteoarthritis may also be caused secondarily by other conditions such as trauma, infections, avascular necrosis, knee ligament insufficiencies and inflammatory arthritis (such as gout and rheumatoid arthritis).

When the osteoarthritis, no matter what the cause, results in progressive knee pain affecting the patients quality of life and function, the patient may be a candidate for a knee replacement. Pain is the single most important indication for surgery. Other less important indications are knee deformities and knee stiffness.

What are the risks of undergoing a total knee replacement?

Complications specific to knee replacements:

  • Blood clots in the lower limb veins (known as deep vein thrombosis or DVT)
  • These blood clots can travel to the lungs, this is known as a Pulmonary Embolism or PE. Although rare a PE can cause respiratory failure and death.
  • Knee dislocations (instability)
  • Infections (superficial wound infection or deep infection involving the knee replacement)
  • scarring and limitation of knee range of motion
  • persistent pain despite the knee replacement
  • Heterotropic ossification - new bone formation in the muscles surrounding the knee.
  • loosening of the knee replacement components
  • Bleeding
  • Anaesthetic related complications such as heart arrhythmias, stroke, liver toxicity, pneumonia and death.

What are the preparations needed for the procedure?

The preoperative evaluation generally includes a review of all medications being taken by the patient. Anti-inflammatory medications, including aspirin, are often discontinued one week prior to surgery because of the effect of these medications on platelet function and blood clotting.

Other preoperative evaluations include complete blood counts, electrolytes (potassium, sodium, chloride), blood tests for kidney and liver functions, urinalysis, chest X-ray, EKG, MRSA (methicillin-resistant Staphylococcus Aureus) screen and a physical examination. Your physician will determine which of these tests are required, based on your age and medical conditions.

Any indications of infection, severe heart or lung disease, or active metabolic disturbances such as uncontrolled diabetes may postpone or defer total hip joint surgery. In these cases, I will ask a specialist physician to consult the patient in order to optimize the medical conditions prior to surgery.

Total knee replacement can involve blood loss. Patients planning to undergo total knee replacement often will donate their own (autologous) blood to be stored for transfusion during the surgery. Should blood transfusion be required, the patient will have the advantage of having his or her own blood available, thus minimizing the risks related to blood transfusions

Excess body weight may be a risk factor for infection, increased intra-operative blood loss, deep vein thrombosis/pulmonary emboli, knee stiffness and persistent knee pain following the surgery. These patients may also have a much slower post-operative rehabilitation recovery period. If at all possible, patients with excess body weight should consider a weight loss program to reduce the risks of Surgery.

What will recovery be like for the patient after surgery?

A total knee joint replacement takes approximately two to four hours of surgical time. The preparation prior to surgery may take up additional time. After surgery, the patient is taken to a recovery room for immediate observation that generally lasts between one to four hours. Upon stabilization, the patient is transferred to a hospital room or Intensive Care Unit.

During the immediate recovery period, patients are given intravenous fluids. Intravenous fluids are important to maintain a patient's electrolytes and replace any fluids lost during surgery. Using the same IV, antibiotics might be administered as well as pain medication. Patients also will notice tubes draining fluid from the surgical wound site. The amount and character of the drainage are important to the doctor and can be monitored closely by the nurse in attendance. A dressing is applied in the operating room and will remain in place for 2 weeks. The dressing is changed earlier only if the wound is oozing or the dressing has come loose.

Pain-control medications are commonly given through a patient-controlled-analgesia (PCA) pump whereby patients can actually administer their own dose of medications on demand. Pain medications occasionally can cause nausea and vomiting. Antinausea medications may then be given.

Measures are taken to prevent blood clots in the lower extremities. Patients are placed in elastic hose (TEDs) after surgery. Compression pumps are often added, which help by forcing blood circulation in the legs. Patients are encouraged to actively exercise the lower extremities in order to mobilize venous blood in the lower extremities to prevent blood clots. Medications are given to thin the blood in order to further prevent blood clots.

Patients may also experience difficulty with urination. This difficulty can be a side effect of medications given for pain. As a result, catheters are often placed into the bladder to allow normal passage of urine.

Immediately after surgery, patients are encouraged to frequently perform deep breathing and coughing in order to avoid lung congestion and the collapse of tiny airways in the lungs. Patients are also given a "blow bottle," whereby active blowing against resistance maintains the opening of the breathing passages.

Total knee replacement facts

  • The prosthesis for Total knee replacements includes a femoral metal cap, tibial metal tray and a plastic button resurfacing of the patella (knee cap).
  • Chronic pain and impairment of the daily function of patients with severe knee arthritis are reasons for considering treatment with total knee replacement.
  • Complications and risks of total knee replacement surgery have been identified and will be discussed with you in detail
  • Preoperative banking of the blood of patients planning total knee replacement is considered when possible. This blood can be used for transfusion if needed (autologous transfusion).
  • Physical therapy is an essential part of rehabilitation after a total knee replacement.
  • Patients with artificial joints are generally recommended to take antibiotics before, during, and after any elective invasive procedures.

How does the patient continue to improve as an outpatient after discharge from the hospital? What are recommended exercises?

For an optimal outcome after total knee replacement surgery, it is important for patients to continue in an outpatient physical therapy program along with home exercises during the healing process. Patients will be asked to continue exercising the muscles around the replaced joint to prevent scarring (and contracture) and maintain muscle strength for the purposes of joint stability. These exercises after surgery can reduce recovery time and lead to optimal strength and stability.

The wound will be monitored by myself and the wound sister. Patients should watch for warning signs of infection, including abnormal redness, increasing warmth, swelling, or unusual pain. It is important to report any injury to the joint to me immediately.

Future activities are generally limited to those that do not risk injuring the replaced joint. Sports that involve running or contact are avoided, in favour of leisure sports, such as golf, and swimming. Swimming is the ideal form of exercise since the sport improves muscle strength and endurance without exerting any pressure or stress on the replaced joint.

Patients with joint replacements should alert their doctors and dentists that they have an artificial joint. These joints are at risk for infection by bacteria introduced by any invasive procedures such as surgery, dental or gum procedures, urological and endoscopic procedures, as well as from infections elsewhere in the body.

The treating physician will typically prescribe antibiotics before, during, and immediately after any elective procedures in order to prevent infection of the replaced joint.

Though infrequent, patients with total knee replacements can require a second operation years later. The second operation can be necessary because of loosening, fracture, or other complications of the replaced joint. Reoperations are generally not as successful as original operations and carry higher risks of complications. Future replacement devices and techniques will improve patient outcomes and lead to fewer complications.

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