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Dr Lipalo Mokete, Specialist Arthroplasty Surgeon

Total Knee Replacement Surgery

What is Arthritis?

Arthritis is a condition whereby joint cartilage is destroyed. The commonest type is osteoarthritis, which may be the result of previous joint injury or mal-alignment of the leg. Idiopathic osteoarthritis is a term we apply to osteoarthritis of indeterminate origin. Another big subset of arthritis is that caused by conditions associated with inflammation within the body. Rheumatoid arthritis is the commonest of these conditions. Other causes of inflammatory arthritis include gout and systemic lupus erythematosus. Occasionally arthritis happens as a consequence of death of the bone around the joint due to lack of blood supply, a condition referred to by the medical term Osteonecrosis.

You may be a candidate for total knee replacement surgery if you have advanced arthritis of the knee with debilitating pain and you are not coping with activities that ordinarily form part of your daily routine. Your family doctor or other health care professional may have already suggested that you need knee replacement surgery. A brief interview followed by examination and review of your radiographs will help confirm whether you are indeed a candidate for knee replacement surgery. You will learn about the risks and benefits of the procedure and only once you are mentally and physically ready to undergo the procedure will we schedule surgery.

What is a Total knee Replacement?

The knee joint consists of three compartments and these may be affected by arthritis to a varying extent.

  1. Patellofemoral Compartment - The compartment between the knee cap (patella) and the lower end of the thigh bone (femoral trochlea).
  2. Lateral Compartment - The compartment between the thigh bone and the lower leg (tibia) on the outside.
  3. Medial Compartment - The compartment between the thigh bone and the lower leg on the inside.

Total knee replacement is a surgical procedure whereby the diseased knee joint is replaced with artificial parts. The articular surface of the femur is resected and replaced with a metal alloy part that is attached to bone. Similarly, the upper part of the tibia, which forms part of the knee joint is also resected and replaced with a metal alloy part. A molded insert made of special plastic (polyethylene) is then placed between the two metal parts to restore smooth movement in the new knee. The articulating surface of the knee cap can also be replaced with a polyethylene part.

The actual surgery takes just over an hour but the entire process of administering anesthetic, doing the surgery and waking you up thereafter takes approximately two and a half hours. Total knee replacement surgery is considered a major surgical procedure.

Patient Specific Jigs in Knee Replacement Surgery

Total knee replacement

One of the main factors that influences longevity of a knee replacement is the alignment of the implanted parts. Knee replacement parts have to be well aligned once implanted in the body to ensure that they perform optimally and last for a minimum of ten years. Conventional methods of aligning the knee during surgery involve the use of specialized instruments, which make use of rods that are inserted into the thigh bone (femur) and at times the lower leg (tibia).

Patient specific instrumentation (PSI) is a recent development. PSI involves pre-operative Cat scans (CT) or Magnetic Resonance Imaging (MRI) of the leg to determine overall alignment and morphology of the knee. The scans are emailed to an Orthopaedic engineering facility where computer models are made of the knee based on the scan information. Appropriate bone cuts of the knee are simulated and instruments are designed to achieve these cuts. Your Orthopaedic surgeon is an intergral part of the process as he has to approve the design of PSI instruments. The instruments are specific to you the patient and the knee to be operated i.e. they cannot be used on other patients and they cannot be used for the right knee if designed for the left knee. Once the surgeon is satisfied with the design, he then gives the engineers the go-ahead to manufacture the PSI instruments. The finished product which, is specific to your knee, is packaged sterilized and then sent to the surgeon in preparation for your surgery. PSI is not a new type of knee replacement but merely a tool that helps in achieving alignment of the knee replacement parts – implanted parts are the same as those used in conventional knee replacements.

If you desire PSI for your knee operation, you have to be aware of these facts:

  1. Your medical aid may not cover the cost of PSI in full, in which case you may have to contribute to the cost of the pre-operative scans.
  2. Once you have committed to PSI, you have to have knee surgery within three months of the scan.
  3. Rarely you may be requested to have the CT scan or MRI scan repeated if the captured images lack the requisite clarity.
  4. This type of surgery may be unsuitable if you have had previous surgery to the knee and have metal plates or screws close to the knee joint.

What to bring to hospital

Expect to be in hospital for five to ten days.Please bring along a change of underwear, night clothes and comfortable loose fitting day clothes like track suit pants, slip on shoes and trainers (takkies). Other essential items include a small bag of toiletries, and reading material.

Free WIFI is available for inpatients in the hospital and there are personal television sets where you can access a select number of channels. Do not forget to bring along your regular walking aid and medication that you normally take.

If you use spectacles, a hearing aid or dentures, you should also bring these items with you. Please do not bring expensive jewelry and mountains of cash. The hospital provides security boxes for personal items with only limited liability

tooth brush

What to expect in hospital

Post-op Information/Expectations

Do's and Dont's following Total Knee Replacement Surgery