TKR: A step-by-step review
A total knee replacement (TKR) is a complex procedure that requires an orthopedic surgeon to make precise measurements and skillfully remove the diseased portions of your bone, in order to shape the remaining bone to accommodate the knee implant. During the procedure, the surgeon builds the artificial knee inside your leg, one component at a time, to create a highly realistic artificial joint.
Read on to find out what will happen to you after you enter the operating room for a TKR.
The surgeon makes an incision across the front of your knee to gain access to the patella, more commonly referred to as the kneecap. In a traditional knee replacement, the incision is usually about 8 to 10 inches long. In minimally invasive knee surgery, the incision is usually about 4 to 6 inches long. The jury is still out as to whether or not the pros of the smaller scar outweigh the cons of a smaller surgical area. Talk to your doctor about which procedure is right for you.
The first part of your knee that is exposed is your kneecap, called the patella. Once your knee is open, the surgeon rotates the patella outside the knee area. This allows the surgeon to view the area needed to perform the surgical procedure.
The first bone your surgeon will resurface is your femur, commonly known as the thighbone. Once the surgeon has opened up and exposed your knee joint, he or she will carefully measure your bones and make precise cuts using special instruments. The damaged bone and cartilage from the end of the femur is cut away. The end of your femur is cut and resurfaced to fit the first part of the artificial knee, the femoral component.
The surgeon attaches the metal femoral component to the end of your femur and uses bone cement to seal it into place.
The next bone your surgeon resurfaces is your tibia, or shinbone. The surgeon removes damaged bone and cartilage from the top of the tibia and then shapes the bone to fit the metal and plastic tibial components.
The bottom portion of the implant, called the tibial tray, is fitted to the tibia and secured into place using bone cement. Once the tray is in place, the surgeon will snap in a polyethylene (medical-grade plastic) insert to sit between the tibial tray and the femoral component, and act as a kind of buffer. This insert will provide support for your body as you bend and flex your knee.
Before returning the patella to its normal position, the surgeon might need to flatten the patella and fit it with an additional plastic component in order to ensure a proper fit with the rest of your implant. The plastic piece, if needed, is cemented to underlying bone.
Your surgeon will bend and flex the knee to ensure that the implant is working correctly, and that alignment, sizing, and positioning is suitable. To complete the procedure, the surgeon will close the incision with stitches or staples, and then bandage it and prep you for recovery. You may leave the operating room with your leg in a continuous passive motion (CPM) machine that will gently bend and flex your new knee for you while you are lying down.