Total knee replacement, as the name implies, completely replaces the knee with artificial implants. This is usually indicated in cases where the knee is damaged beyond repair, such as in advanced cases of arthritis, or physical trauma. The replacement procedure, also known as arthroplasty, uses metal and polyethylene parts to replace the ends of the femur (or thigh bone) and tibia (shin bone).
The artificial knee implants glide together to replicate the motion of the knee joint. The metal and polyethylene are made from materials that do not interact with the body, hence their safety for implantation.
While the basic motion of the knee is a “hinge joint” that bends and straightens, the knee is actually more complex, as the bone surfaces actually roll and glide as the knee bends. There are three bone surfaces that are replaced in knee arthroplasty:
- Femoral component. The metal femoral component is attached to the lower end of the femur. This is usually curved around the lower end, and is grooved for smooth movement of the kneecap up and down as the knee flexes and extends.
- Tibial component. This is found at the upper portion of the tibia. It is usually designed as a flat metal platform, coupled with a cushion of strong, durable polyethylene plastic. There are some designs that do away with the metal portion and directly attach the polyethylene to the bone. The metal portion can sometimes have a stem that is inserted directly into the tibia for stability.
- Patellar component. This is a duplicate of the patella, and is usually made of polyethylene.
Insertion of the Femoral Implant
The Beverly Hills knee surgeon uses drills and bone cutting tools to reshape the femoral end to match the shape of the metal femoral implant. The procedure is guided by specialized instruments to ensure alignment and accuracy. The femoral implant is then placed on the reshaped area of the femur. The implant is stabilized and fixed in place with stabilizing pins.
If the damage extends to the kneecap, the surgeon will use instruments to resect the interior surface of the patella into a flat shape. The polyethylene patellar component is then fixed to the reshaped patella through pins and bone cement.
The tibia is then prepared for implantation through a process similar to the femur. The damaged parts of the bone are removed and reshaped to match the tibial component. Specialized instruments are used to guide and align this reshaping process. Once the proper shape has been achieved, bone cement is used to secure the metal portion of the implant onto the tibial head. The polyethylene portion of the implant is then inserted onto the metal portion to provide a smooth surface for the femoral component to slide on during flexion and extension.
The Los Angeles knee replacement surgeon conducts several examinations and tests during the operation to make sure the correct fit and placement of the implants is achieved. The range of motion and the degree of joint mobility is assessed to ensure the patient regains maximum function in the replaced knee. If the components are too large, range of motion may be limited postoperatively.