Knee joint prosthesis, knee joint endoprosthesis, total knee stent endoprosthesis, knee TEP, total endoprosthesis (TEP), artificial knee joint
Definition
A knee prosthesis replaces the worn part of the knee joint with an artificial surface. The worn layers of cartilage and bone are removed during surgery and replaced by two artificial parts, namely the femoral shield and the metallic tibial plateau. In order to prevent these two joint surfaces from rubbing against each other and thus metal parts from being embedded in the joint, a so-called plastic sliding surface is inserted between the two components. This plastic sliding surface thus lies between the thigh and the tibia.
Construction of a knee prosthesis
As can be seen from the figure below, a knee prosthesis consists of at least two different components: the femur and the tibia. While these two components must always be replaced, it is not absolutely necessary to replace the back surface of the patella.
- The thigh part of the knee prosthesis (=femur component), usually consists of a cobalt-chrome alloy
- The tibia part of the knee prosthesis (= tibia plateau) consists of a metal component on which an inlay, the plastic support (= sliding surface), rests.
- The patella part of the knee prosthesis is made of very hard plastic (polyethylene).
It is not absolutely necessary to replace this surface.
- Thigh bone (femur)
- Thigh (femur) component
- Lower leg (tibia) component
- Shinbone (Tibia)
- Calf bone (fibula)
Since the first knee prosthesis, both the surgical methods and the materials used have changed and developed further. Depending on the manufacturer, different materials are used for knee prostheses today. Often different materials are used within a prosthesis to achieve the best possible result.
For example, the so-called “bicondylar knee TEP“, one of the most common prostheses, uses high-quality metals such as stainless steel or oxinium and titanium, as well as a special plastic (polyethylene). The metal is fixed to the thigh as well as the lower leg bone. A plastic disc is then placed on the lower piece, on which the upper part can slide.
In order to make the stainless steel hard enough for use as a prosthesis, so-called alloys are used. Chrome-cobalt alloys are used in particular. Since allergies to these alloys are known, in individual cases ceramic implants or so-called allergy implants can be used, where particularly low-allergy alloys are used. You can find more information on this topic here: Material of knee prostheses
