Over the past 20 years, artificial knee replacement surgery has become increasingly common. Millions of people have gotten a new knee joint. The first time a joint is replaced with an artificial joint the operationis called a primary joint replacement. As people live longer and more people receive artificial joints, some of those joints begin to wear out and fail. When an artificial knee joint fails, a second operation is required to replace the failing joint. This procedure is called a revision arthroplasty.
Rationale
Why does a knee revision become necessary?
The most common reasons for knee revision arthroplasty are :
• mechanical loosening
• infection in the joint
• fracture of the bone around the joint
• instability of the implant
• wear of one or more parts of the implant
• breakage of the implant
Mechanical Loosening / Aseptic Loosening Mechanical loosening means that, for some reason (other than infection), the attachment between the artificial joint and the bone has become loose. There are many reasons why this can occur. It may be that, given enough time, all artificial joints will eventually loosen. This is one reason that surgeons like to wait until absolutely necessary to put in an artificial joint. The younger you are when an artificial joint is put in, the more likely it is that the joint will loosen and require a revision.
Infection
If an artificial joint is infected, it may become stiff and painful. It may also begin to lose its attachment to the bone. An infected artificial joint will probably have to be revised to try to cure the infection.The surgery may be a one-stage exchange or more often a two-stage exchange. In rare cases, the knee may need to be fused together, or possibly even amputated.
Fracture
A fracture may occur near an artificial joint. It is sometimes necessary to use a new artificial joint to fix the fracture. For example, if the femur (thighbone) breaks where the prosthesis attaches, it may be easier to replace the femoral part of the artificial joint with a new piece that has a longer stem that can hold the fracture together while it heals. This is similar to fixing the fracture with a metal rod.
Instability
Instability means that the artificial joint dislocates. This is very painful when it happens. It is unlikely that the knee joint will completely dislocate. However, it can happen. It is more common for the knee joint to be either too tight or too loose. If the knee joint is too loose, it can cause unsteadiness and pain. If the joint is too tight, the knee is usually painful and doesn't have a good range of motion.
Wear
With the rise in knee joint replacements, surgeons have begun to see wear in the plastic parts of the artificial joints. In some cases, if the wear is discovered in time, the revision may only require changing the plastic part of the artificial joint. If the wear continues until the metal is rubbing on metal, the whole joint may need to be replaced.
Breakage
Finally, the metal of the artificial joint can break due to the constant stress that the artificial joint undergoes everyday. In weight bearing joints like the knee, this is greatly affected by how much you weigh and how active you are.
Limitations of Revision Knee Replacement
A revision joint replacement of the knee is more complex and unpredictable than a primary joint replacement. Since many factors can influence its longevity, your surgeon will not be able to say exactly how long your revision will last. Also, keep in mind that because revision surgery is more complicated than primary joint replacement, it may take more time than a primary surgery to be able to perform your routine daily activities. Often people continue to need a walking aid because knee pain increases when they are on their feet for prolonged periods. There is also a greater chance that the knee will be tight and unable to bend all the way after knee revision surgery.
In some cases, if an artificial joint fails, it may not be possible to put another artificial joint back in. This can occur if the primary joint has failed because of an infection that cannot be controlled, if the bone has been destroyed so much that it will not support an artificial joint, or if your medical condition will not tolerate a major operation.
Sometimes a choice other than knee revision is best because a big operation might result in a failure, or even death. Removing the prosthesis and not replacing it doesn't mean the patient can't walk anymore. The surgeon may suggest fusing the joints of the knee, placing a spacer in the joint, or in some cases amputating the leg.
Complications
As with all major surgical procedures, complications can occur.
Some of the most common complications following revision arthroplasty of the knee include
1. Medical / Anaesthesia complications
2. Thrombophlebitis / DVT
3. Infection
4. Loosening
5. Incision & wound complications
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