Total knee arthroplasty surgery is performed under sterile conditions in the operating theatre under spinal or general anesthesia. You will be lying on your back and a tourniquet applied to your upper thigh to reduce blood loss. The surgeon makes an incision along the affected knee, exposing the knee joint. The surgeon first concentrates on the femur (thighbone).
The damaged portions of the femur are then cut at the appropriate angles using specialized jigs. The femoral component is attached to the end of the femur with or without bone cement. The damaged area of the tibia (shinbone) and the cartilage are cut or shaved. This removes the deformed part of the bone and bony growth, as well as allows for a smooth surface for which to attach the implants. The tibial component is secured to the end of the bone with bone cement or screws depending on a number of factors and on surgeon’s choice. The surgeon will place a plastic piece called an articular surface between the implants to assure a smooth gliding movement. This plastic insert will support the body’s weight and allow the femur to move over the tibia, similar to the original cartilage (meniscus). The femur and the tibia with the new components are put together to form the new knee joint. To make sure the patella (knee cap) glides smoothly over the new artificial knee: its rear surface is prepared to receive a plastic component. With all the new components, the knee joint is tested through its range of motion.
All excess cement will be removed. The entire joint will be irrigated or cleaned out with a sterile saline solution. The knee is then carefully closed and drains usually inserted and the knee dressed and bandaged.
Risks and Complications
- As with any major surgery there are potential risks involved. The decision to proceed with the surgery is made because the advantages of surgery outweigh the potential disadvantages.
- It is important that you are informed of these risks before the surgery takes place.
Complications can be medical (general) or local complications specific to the knee
Medical complications include those of the anesthetic and your general wellbeing. Almost any medical condition can occur so this list is not complete. Complications include
- Allergic reactions to medications
- Blood loss requiring transfusion with its low risk of disease transmission
- Heart attacks, strokes, kidney failure, pneumonia, bladder infections
- Complications from nerve blocks such as infection or nerve damage
- Serious medical problems can lead to ongoing health concerns, prolonged hospitalization or rarely death.
- Stiffness in the knee Ideally your knee should bend beyond 100 degrees but on occasion the knee may not bend as well as expected. Sometimes manipulations are required. This means going to theatre and under anesthetic the knee is bent for you.
- Wound irritation or breakdown The operation will always cut some skin nerves, so you will inevitably have some numbness around the wound. This does not affect the function of your joint. You can also get some aching around the scar. Vitamin E cream and massaging can help reduce this. Occasionally you can get reactions to the sutures or a wound breakdown which may require antibiotics or rarely further surgery.
- Infection can occur with any operation. In the knee this can be superficial or deep. Infection rates are approximately 1%. If it occurs it can be treated with antibiotics but may require further surgery. Very rarely your knee prosthesis may need to be removed to eradicate the infection.
- Blood clots (Deep Venous Thrombosis) These can form in the calf muscles and can travel to the lung (Pulmonary embolism). These can occasionally be serious and even life threatening. If you get calf pain or shortness of breath at any stage, you should notify your surgeon.
- Damage to nerves or blood vessels Also rare but can lead to weakness and loss of sensation in part of the leg. Damage to blood vessels may require further surgery if bleeding is ongoing.
- Wear The plastic liner eventually wears out over time, usually 10 to 15 years, and may need to be changed.
- Cosmetic Appearance The knee may look different than it was because it is put into the correct alignment to allow proper function.
- Dislocation An extremely rare condition where the ends of the knee joint lose contact with each other or the plastic insert can lose contact with the tibia (shinbone) or the femur (thigh bone).
- Patella problemsPatella (knee cap) can dislocate that is, it moves out of place and can break or loosen.
- Ligament injuries There are a number of ligaments surrounding the knee. These ligaments can be torn during surgery or break or stretch out any time afterwards. Surgery may be required to correct this problem.
- Fractures or breaks in the bone can occur during surgery or afterwards if you fall. To fix these, you may require surgery.