Knee prostheses are classified according to how the affected bones are replaced, differentiating between total knee, unicompartmental or revision prosthesis. Here we will see the differences and how they are fixed to the bone.
What is knee prosthesis?
Knee prostheses are classified according to how the affected bones are replaced, but the most common are those known as total knee prostheses (PTR). The PTR are fixed to the tibia using a metallic tibial tray and to the femur through condyles, also metallic. Between them, there is a piece called insert and made of a plastic (polyethylene) that facilitates the articulation of the femur and tibia. If the surgeon considers it appropriate, you can also replace the joint part of the kneecap with a polyethylene component.
The fixation of the elements to the bone can be using bone cement or looking for the integration of these bone (depending on the bone quality of the patient).
What types of knee prostheses are there in the market?
A knee prosthesis is used to prevent pain and restore function to patients suffering from joint wear. Depending on the type of wear, the stability of the soft tissues or the existence of previous surgeries, you may be a candidate for the implantation of one or a different kind of knee prosthesis. Among the most common, we can name the following:
Unicompartmental knee prosthesis: Its primary indication is the treatment of knee arthrosis that only affects one side of the joint. It is assumed that, as not the whole knee is affected, prosthetic replacement should be limited to damaged regions. However, many surgeons do not use it because it does not prevent the progression of the disease to the other side and because there is not much experience in its use. Its components are the same as in a total prosthesis, but only for one half of the knee.
Total knee prosthesis: It is the most common type of knee prosthesis. Knee replacement surgery in India consists of a complete replacement of the two joint surfaces and, as we discussed in the previous section, it is composed of the following components:
Tibial tray: Made of metal (usually cobalt chrome or titanium alloys), fixes the prosthesis to the proximal tibia.
Femoral component: It is fixed to the distal part of the femur and acts as a friction surface, so it is usually manufactured in cobalt-chromium.
Insert: It is located between the two previous components and acts as a friction surface together with the femoral component. It is usually made of polyethylene.
Patellar component: Not used in all cases and its use depends on the personal preferences of the surgeon. It is usually made of polyethylene.
Revision knee prosthesis: These are the systems used when replacing an implanted prosthesis. In the most straightforward cases, primary total prostheses may be placed, but there are also implants designed explicitly for these complex procedures. In revision surgeries, there are usually problems of stability and lack of bone. To fill the defects in the bone is used biological products or additional prosthetic elements such as stems or supplements. To stabilize the joint, more constricted prosthetic designs and even hinge-type knees may be applied by the orthopedics surgery hospitals in India. The revision knees can also be used in other types of cases in which there has been a significant loss of bone mass, such as tumors.