After the appropriate preoperative preparations are completed and the patient is asleep, the surgical procedure will begin. A tourniquet is used to minimize bleeding during the surgical procedure. Blood is exsanguinated from the leg using either gravity or a wrap and the tourniquet is inflated. A straight surgical incision, varying in length depending on the patient’s size and anatomy, is made. A longitudinal incision through the retinaculum, which lies next to the kneecap, is made and the kneecap is translated laterally. This type of approach is an evolution of the classic total knee approach and minimizes the amount of exposure and avoids deviation of a long segment of the quadriceps tendon.
Total knee replacement involves making a series of cuts removing a relatively thin piece of bone from the top surface of the tibia, or shinbone, and from the lower and front/back of the femur, or thighbone. The amount of bone removed is generally 8 to 10 mm in thickness and corresponds with the thickness of the implant that will replace the bone removed. A series of five or six cuts are made on the end of the thighbone and one transverse cut is made on the top of the shinbone. The kneecap is resurfaced by making a flush cut across the surface of the kneecap and this is then resurfaced with a polyethylene implant. Trial components are then placed to check the alignment of the limb, the position of the components, and the tracking of the implants against one another. We will use a variety of techniques to assess alignment, including mechanical alignment rods and computer-assisted technology. Once we are satisfied with the alignment and component placement, we check soft tissue stability to makes sure that the knee is balanced both in full extension as well as flexion. The key to a successful outcome is making sure that the knee is balanced throughout the arc of motion and that the correct alignment has been obtained. Following these checks, the trial implants are removed and fixation holes for the real implants are created on the ends of the bone.
We clean the bony surface with a water pick type device that sprays sterile fluid on the bone, cleaning blood, fat, and debris from the surface of the bone so that good interdigitation of the cement can be accomplished. Bone cement is then mixed, adding a liquid to a powder which then becomes a doughy substance. This is placed across the ends of the bone and pressurized into the bone and the implants are placed on the ends of the bone compressing the cement into the implant and the bone. Excess cement is removed and after hardening of the cement, which normally takes between 10 and 15 minutes, the implant is fixed to your bone, mechanically stable, and able to tolerate the rigors of daily activity.
The knee is then irrigated vigorously with sterile antibiotic solution. The joint is closed up with sutures, the skin closed with staples, sterile dressings are applied, and the patient is taken to the recovery room. The rehabilitation process begins about two to three hours later when the patient arrives on the ward and gets up bearing weight as tolerated on the leg using a walker or crutches.
