Surgical Procedure
Total Knee Replacement Surgery with the NexGen LPS-Flex Fixed Knee
The knee is the hinge joint consisting of three bones. The upper part of the hinge is at the end of the upper leg bone (femur), and the lower part of the hinge is at the top of the lower leg bone (tibia). When the knee is bent, the end of the femur rolls and slides on top of the tibia. A third bone, the kneecap (patella), glides over the front and end of the femur.
In a healthy knee joint, the surfaces of these bones are very smooth and covered with a tough protective tissue called cartilage. Osteoarthritis causes damage to the bone surfaces and cartilage where the three bones meet and rub together. These damaged surfaces can eventually become painful.
There are several ways to treat the pain caused by osteoarthritis. One way is a total knee replacement surgery. The decision to have total knee replacement surgery should be made very carefully after consulting your doctor and learning as much as you can about the knee joint, osteoarthritis, and the surgery.
In some cases, the Flex Fixed Knee may be an option for total knee replacement. The basic surgical procedure for the Flex Fixed Knee is the same as for any other total knee replacement.
In total knee replacement surgery, the bone surfaces and cartilage that have been damaged by osteoarthritis are removed and replaced with artificial surfaces made of metal and a plastic material. We call these artificial surfaces "implants," or "prostheses."
Getting to the Joint
The patient is first taken into the operating room and given anesthesia. After the anesthesia has taken effect, the skin around the knee is thoroughly scrubbed with an antiseptic liquid. The knee is flexed about 90 degrees and the lower portion of the leg, including the foot, is placed in a special device to securely hold it in place during the surgery. Usually a tourniquet is then applied to the upper portion of the leg to help slow the flow of blood during the surgery.
An incision is then made that typically extends from just above the knee to just below the knee. The incision is gradually made deeper through muscle and other tissue until the bone surfaces are exposed.
Removing the Damaged Bone Surfaces
The damaged bone surfaces and cartilage are then removed by the surgeon. Precision instruments and guides are used to help make sure the cuts are made at the correct angles so the bones will align properly after the new surfaces (implants) are attached.
Small amounts of the bone surface are removed from the front, end and back of the femur. This shapes the bone so the implants will fit properly. The amount of bone that is removed depends on the amount of bone that has been damaged by the osteoarthritis.
A small portion of the top surface of the tibia is also removed, making the end of the bone flat.
The back surface of the patella (kneecap) is also removed.
Attaching the Implants
An implant is attached to each of the three bones. These implants are designed so that the knee joint will move in a way that is very similar to the way the joint moved when it was healthy. The implants are attached using a special kind of cement for bones.
The implant that fits over the end of the femur is made of metal. Its surface is rounded and very smooth, covering the front and back of the bone as well as the end.
The implant that fits over the top of the tibia usually consists of two parts. A metal baseplate fits over the part of the bone that was cut flat. A durable plastic insert is then attached to the baseplate to serve as an articulating surface between the baseplate and the metal implant that covers the end of the femur.
The implant that covers the back of the patella is also made of a durable plastic.
Artificial knee implants come in many designs. The surgeon will choose the implant design that best meets the patient's needs.
Knee Implants After Attachment
Closing the Wound
If necessary, the surgeon may adjust the ligaments that surround the knee to achieve the best possible knee function.
When all of the implants are in place and the ligaments are properly adjusted, the surgeon sews the layers of tissue back into their proper position. A plastic tube may be inserted into the wound to allow liquids to drain from the site during the first few hours after surgery. The edges of the skin are then sewn together, and the knee is wrapped in a sterile bandage. The patient is then taken to the recovery room.
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