Total Knee Replacement

Anatomy
The knee joint is the largest joint in the body. The bones that make up the knee joint are the end of the femur (thigh bone), the top of the tibia (shin bone) and the patella (kneecap). These bones are all covered with articular cartilage, a material that allows the bones of the knee to move smoothly over each other.

Another type of cartilage, called the meniscus, acts as a cushion between the femur and tibia, providing a shock absorption function in the knee joint during weight bearing activities. A number of ligaments and tendons help to provide stability and strength to the knee joint.

Arthritis of the knee joint
Arthritis is a condition where the joint cartilage at the ends of the bones wears away, causing roughened bone surfaces. This can result in pain, stiffness, swelling and reduced movement of the joint.

There are a few different types of arthritis, outlined below:

- Osteoarthritis (OA):An age related arthritis, where the cartilage is worn away over time.
- Rheumatoid arthritis (RA):A chronic inflammatory type of arthritis which destroys the joint cartilage. It can occur at any age.
- Post-traumatic arthritis: Arthritis may develop after an injury to the bones of the knee joint.

The end result of the various forms of arthritis is a destroyed and painful joint.

Non-operative Treatment
Initially, you may find relief from your knee arthritis by some or all of the following methods: the use of analgesic/anti-inflammatory medications; avoiding/reducing activities that aggravate your arthritis, running and walking; participating in exercises such as swimming or bike riding to help improve muscle strength and joint mobility; losing weight to reduce the load on your knee joints.

Steroid and Synvisc (artificial lubricant) injections can be helpful.

If the above methods do not help with the pain and other symptoms of arthritis, a total knee replacement may be suggested.

BEFORE YOUR OPERATION
Before your operation, Dr Mansfield will discuss with you your general health and any existing medical conditions. It may be necessary, in the interest of your forthcoming surgery, to refer you to a physician with the aim of maximising your health status and potential recovery prior to surgery.

Infection is a big risk and you will be involved in applying our infection control protocols, prior to surgery, as part of our clinical management strategy to reduce your risk of acquiring a postoperative infection.

In that regard, it is important that the integrity of the skin around the operation site is maintained clean with no cuts, abrasions, pimples or any other breaches. The presence of any of these may result in surgery delay because the risk of acquiring an infection is high. Should you have any doubts or concerns with regard to this requirement, please contact Dr Mansfield or the practice staff to seek clarification. Surgical skin preparation is attended in the operating suite DO NOT SHAVE your own leg.

Anticoagulants, (blood thinners) such as Warfarin, Clopidogrel, Aspirin and Cartia may cause bleeding and need to be considered and assessed prior to surgery. Please inform Dr Mansfield if you are on any of these medications as it is usually necessary to cease them for a period prior to surgery.
Routine oral medications, excluding oral hypoglycaemic agents, may be taken the morning of the surgery with a small amount of water. With Diabetic medications only half should be taken and diabetic patients will be scheduled first on the list in order to prevent hypoglycaemia.

Should you have a previous history of DVT’s or venous thromboembolism this will place you in a high risk group. Whilst the risk of deep vein thrombosis is managed prophylactically in every patient, you must inform Dr Mansfield of your previous history in order that any extra precautions necessary may be implemented.

Smoking brings with it many serious health hazards including increased risk of acquiring a postoperative infection and poor wound healing. The infection rate increases more than 4 times in smokers therefore this is a good time to make the brave move and take up the challenge to stop smoking prior to surgery.

Operative Treatment - Total Knee Replacement
A total knee replacement (TKR) involves the removal of the affected worn knee joint surfaces and replacing them with prosthesis. Usually, just the femur and tibia are replaced, however if you are having TKR because of rheumatoid arthritis, the patella may also be replaced.

The prostheses for the femur and tibia are made of a very high grade medical stainless steel, with a plastic (high density polyethylene) insert between them that acts as a bearing surface and prevents the metal prostheses rubbing against each other. The patella prosthesis is also plastic. The knee system I use does not require cementing of the prostheses into place, as the prostheses have a porous coating which allows bone ingrowth and hence a biological union of the prosthesis to bone.

Post-operative Course
Following a TKR, you will usually stay in hospital for 5-10 days. During this time, you will begin mobilization with a splint on your knee. It is important to keep the splint on for the first 2-3 weeks whenever you are walking. Make sure you rest to allow your knee to heal, and remember walking should only be for necessity, not as an exercise. Continue to do any other exercises you have been shown by the physio. Remember full extension (flattening the knee onto the bed) is most important.

The waterproof dressing on your knee will stay on until you visit us in the rooms about 2 weeks after surgery, when you will have your skin staples removed. A small amount of fluid may build up underneath this dressing. This is usual and helps the wound to heal.

You maybe prescribed oral anti-coagulant therapy for the prevention of DVT.

It is normal for you have to some level of pain after a knee replacement. You will be given a script for analgesics when you are discharged from the hospital. After the initial few post-op weeks, regular doses of paracetamol during the day may provide adequate pain relief, if required. The healing time for a TKR is at least 3 months. Patience is required. Your knee will be hot, swollen and sore during this time. Excess activity will aggravate these symptoms.

As your knee replacement settles and your activity increases, high impact or demanding activities must be avoided, such as jogging or contact sports. The new knee is extremely durable but still susceptible to wear and tear. The best aerobic activity following a TKR is bike riding, as it places very little stress on the knee joint. Golf, swimming and light hiking/walking are also suitable physical activities following a TKR.

You may resume driving a car when your knee feels stable and is able to tolerate your full weight. This is at about 6 weeks for a left knee replacement and 12 weeks for a right knee because of your need to use the brake pedal.

Practice perspective
I have used just 4 types of knee prostheses, since 1981, changing as improvements and understanding has occurred.

Since 1991, I have used the LCS (Low Contact Stress) mobile bearing un-cemented prosthesis. I have performed over 500 procedures and my results parallel international experience with this prosthesis.

A recent manufacturing problem with the LCS femur and subsequent company response to this matter has led me to reassess my situation and I have changed to using the Advantim Total Knee Replacement. I made this decision because looking at the Australian National Joint Registry the Advantim is the best performed prosthesis on our registry.

The Advantim is a fixed bearing replacement with tibial fixation using pegs, stem fins and screws. The excellent results demonstrated with this prosthesis are as seen in the tables below.

(Registry 2009)
Table KT24: Revision Rate of Primary Total Knee Replacement with Cementless Fixation

Table KT 25: Yearly Cumulative Percent Revision of Primary Total Knee Replacement with Cementless Fixation (Revisions per 100 Observed Component Years)

Reference: Australian Orthopaedic Association National Joint Replacement Registry 'Hip And Knee Arthroplasty September 1999 to December 2008' Annual Report 2009, 147-148.

I continue to treat and support my patients who were unfortunate to be the recipents of the LCS DuoFix femoral prosthesis with its inherent manufacturing defect. This has led to serious problems with pain, stiffness and loosening of this prosthesis, requiring many of these patients to undergo revision procedures.

The protocols for the treatment of this problem were formalised at a meeting on 13 August 2011. The meeting was sponsored by Johnson & Johnson and conducted in Melbourne where six members of the Australian Orthopaedic Association with extensive experience with the LCS DuoFix femoral prosthesis and subsequent problems met and developed, with consensus, the following protocols for the management of this problem.

Management of DuoFix Femoral TKR
Zicat, Keene, Brumby, Mansfield, Fettke, Miniter

Prologue
The above named surgeons have had a significant cumulative experience with use of the LCS DuoFix Femoral Components, and have collaborated to outline some of the clinical issues related to management of these device failures.  This information has been summarised here, for the benefit of any surgeons having to investigate and treat patients with these implants in situ.

All LCS DuoFix Femoral Components were inserted between May 2006 to July 2009.  The LCS DuoFix Femoral Components were recalled by Johnson & Johnson at the end of July 2009.

It appears that the principal cause of failure is related to alumina ceramic particles and third body wear, but the pathogenesis remains uncertain.
We are providing an algorithm for management based on our early experience with failure of knee arthroplasty with LCS DuoFix Femoral Components, and some guidelines for surgical technique in revisions, based on this experience.

Investigation
It is our recommendation that all patients known to have this implant in situ be contacted and reviewed to look for symptoms, or signs of implant failure.
Blood tests, ultrasound, bone scan and plain radiographs are often normal or equivocal, and may not be helpful.  The clinical picture is more reliably diagnostic.
Please see attached algorithm for management of these cases.
The common findings have been:

• Development of pain, swelling, stiffness, loss of range of motion, effusion
• Deep scratching of the femoral and tibial components
• Potential for lack of bone ingrowth of both femoral and tibial components
• Soft tissue staining with metal debris
• Debris invasion into intact patellar bone
• Synovitis
• Osteolysis
• Capsular thickening

Revisions
There may be a higher rate of re-revisions in this group, and the results may not be as good as with standard revision arthroplasty.
Experience to date suggests the following considerations when planning revision surgery:

• Consideration of the potential for retained alumina debris requires more aggressive debridement of bone and soft tissue
• Complete synovectomy and consider use of arthroscopic shaver for less accessible areas;  synovectomy and liner change alone has a high rate of recurrence of osteolysis, synovitis and failure
• Liner change and single component revisions are not recommended
• Resect visibly affected bone
• Revise with stemmed femoral and tibial implants;  primary implants used for revision have had a much higher failure rate
• Consider metaphyseal sleeves for reconstruction, and augments
• Un-resurfaced patella requires resurfacing, as debris can invade subchondral bone
  
  

computer navigated knee replacement
Over recent years computer navigation has been used to direct the surgeon’s bone cuts in performing a total knee replacement. This technology was introduced on the assumption that it would improve the precision and reproducibility of insertion of a total knee replacement and it gained almost cult status in the orthopaedic world. However; many experienced surgeons raised questions about this new technology and had doubts about its efficacy and so did not take it up.

For the first time we now have irrefutable statistical evidence from the Norwegian Arthroplasty Registry (GØthesen O 2011:82) that in fact the short – term results of the computer navigated knees are in fact worse than those done without computer navigation and surgeons and patients should be wary of navigation based on these results. Unpublished data from the Australian Joint Registry shows no benefit from navigation in results.

Follow the link to access the reference document:
http://nrlweb.ihelse.net/Forskning/Publikasjoner/Art_Acta_ØGøthesen_
Computernavigation2011.pdf

Risks/Complications
Post –operative complication may include:

• Infection of the skin wounds or knee joint
• Bleeding into the joint
• Blood clot (thrombosis)
• Failure of biological union of the prosthesis to bone, leading to loosening
• Plastic insert failure
• Prolonged knee pain or stiffness

GØthesen O, Espehaug B, Havelin L, Petersson G, Furness O. "Short-term outcome of 1,465 computer–navigated primary total knee replacements 2005-2008." ActaOrthopaedica, 2011:82: 293-300.

Registry, Australian Orthopaedic Association National Joint Replacement. "Hip and Knee Arthroplasty September 1999 to December 2008." Annual Report 2009, 147-148, 2009: 147 - 148.

Zicat, Keene, Brumby, Mansfield, FettkeMiniter. Management of Duofix Femoral TKR. LCS Duofix Management Reference Group, 2011.