Joint replacement surgery has enhanced the quality of life for many people who suffer from advanced arthritis, says the American Academy of Orthopaedic Surgeons. The knee joint proves one of the most frequently replaced joints in the human body, followed closely by the hip. There are three major components of a total knee arthroplasty; the femur, or thigh bone; the tibia or shin bone and the patella, or knee cap. Components come in a variety of sizes and materials to accommodate virtually any size knee.
The Femur
The femoral component is metallic in construction, typically of a substance called cobalt chrome. It is shaped very similar to the configuration of the condyles, or knuckles of the femur. The metallic surfaces are polished to an ultra high gloss finish to provide smooth, almost frictionless motion when bending and straightening the knee.
In instances where only one portion of the femur needs replacement, physicians use a component called a uni-compartmental femoral component. This component resurfaces only one side of the knee joint, leaving the opposite, normal side intact. This uni-compartmental femoral component consists of the same materials as its total femoral counterpart.
These parts can be implanted with either the use of a special bone cement, or cement-less with a component that has a rough, porous coating on the backside that contacts the host bone.
Femoral components can come with a central notch cut into it to accept post located on the plastic tibial insert, called posterior stabilized, or a solid metal accepting a different shaped plastic, called anterior stabilized or cruciate ligament retaining components.The femoral component is metallic in construction, typically of a substance called cobalt chrome, says the Arthritis Foundation. It has a shape very similar to the configuration of the condyles, or knuckles of the femur. The metallic surfaces have an ultra high gloss finish to provide smooth, almost frictionless motion when bending and straightening the knee.
In instances where only one portion of the femur needs replacement, surgeons use a component called a uni-compartmental femoral component. This component resurfaces only one side of the knee joint, leaving the opposite, normal side intact. This uni-compartmental femoral component consists of the same materials as its total femoral counterpart.
Surgeons can implant these parts with either the use of a special bone cement, or cement-less with a component that has a rough, porous coating on the backside that contacts the host bone.
Femoral components can come with a central notch cut into it to accept post located on the plastic tibial insert, called posterior stabilized, or a solid metal accepting a different shaped plastic, called anterior stabilized or cruciate ligament retaining components.
The Tibia
The tibia, or shin bone, component consists of a metallic base plate that is sized, and then anchored to the flat cut surface of the host bone by either cemented or cement-less technique. This base plate may have four short studs or one larger stem on the underside that help anchor the plate into the host bone and can provide additional stability.
The Tibial Spacer
The tibial spacer consists of space-age plastic called ultra-high-molecular-weight-polyethylene, says the American Academy of Orthopaedic Surgeons. One side has a curved surface to contact the rounded knuckles of the femur, while the other side is flat and snaps onto the flat tibial base plate. These spacers come in different thicknesses that allow the surgeon to restore proper ligament tension of the knee joint. The spacers allow the knee to bend and straighten without two metallic surfaces rubbing together. In instances where one side of the knee needs replaceing, the tibial components, both metal and plastic, come in uni-compartmental versions.
The Patella
The patella or knee cap is typically a plastic dome-shaped component. It has a round shape and comes in a variety of diameters and thicknesses to allow for proper recreation of the natural thickness of the knee cap, as well as proper tension of the large tendons the connect to the patella; the quadriceps, or thigh area, tendon and the patella tendon, which connects the patella to the top of the shin bone, says the Arthritis Foundation.
