Revision Knee ReplacementWith newer implant designs and improved surgical techniques, total knee replacements are expected to function well for at least 12 to 15 years in more than 90% of patients. However, some procedures will fail and require a second surgery, called Revision Knee Replacement. Revision Knee Replacement is, thus, an operation in which all or some parts of the previously implanted knee joint are replaced.
Why is Revision Knee Replacement necessary?The knee implants can fail due to several reasons. Some of them include wear and tear leading to loosening, infection, fracture, instability and factors related to the patient.
Though the implants are fixed well to the bone, usually with cement, at the time of knee replacement, over the period of time, friction caused between the joint surfaces generates wear particles which evoke an inflammatory response leading to destruction of the bone (this condition is called osteolysis). This would cause loosening of the joint. This is called non infective or aseptic loosening. It is the most common cause of failure of knee replacement.
Another common reason for which a knee is revised is infection. Infection can occur immediately after surgery which is called early postoperative infection. It can also occur late, months or even years after surgery which is usually due to spread of infection from other part of the body (e.g. tooth, urinary infection or respiratory infection) via blood stream. It is usually treated with immediate cleaning of the infected joint followed by a long course of antibiotics. If this fails to cure the infection or if the joint components have become loose, a revision surgery is required.
- Patient-Related Factors
Longevity of the joint would depend on many factors like patient’s body weight, quality of bones, life style and most importantly the care patient has taken to preserve the joint. Younger, more active patients and obese patients have a higher incidence of wear and loosening.
There are other less common causes like instability and stiffness of knee for which a knee revision is sometimes performed.
What is the difference between a Primary Knee Replacement and Revision Knee Replacement?In primary knee replacement, the native arthritic joint is replaced by artificial knee joint. In Revision Knee Replacement, already implanted knee joint components have to be removed first very carefully to prevent damage to the underlying bone. After removing all the components and cement of the previous surgery, a new joint is implanted.
If revision surgery is being done for infection, it is usually performed in two stages. The components are removed in the first stage and the knee joint is thoroughly cleaned. An antibiotic impregnated cement spacer is placed between the femur and tibia bones to keep the bones apart to facilitate second stage revision surgery and for local delivery of antibiotics in the joint for control of infection. This is followed by about 6-8 weeks course of antibiotics. Once the infection comes under control, second surgery is carried out when the cement spacer is removed and a new joint is implanted.
Also, in revision surgery, more complex knee joint implants may be required due to loss of underlying supporting bone and incompetency of surrounding ligaments around the knee. This makes revision knee replacement surgery more complex and demanding than the primary knee joint replacement.