Treatment Options for Failed Total Knee Replacements
Treatment of the failed or infected total knee is very individualized. The basic rule of thumb is to fix what is “broken.” Typically, the implants used in revision surgery are different than the original implants. The revision implants typically use stems that go inside the shaft of the femur and tibia. The stems help to gain fixation. Some of these implants actually replace parts of the femur or tibia that are missing due to osteolysis (bone loss) or as a result of removing the failed implants.
Many times, bone graft is used in revision surgery. Bone graft may be obtained from another area of the body or may be “off the shelf.” The “off the shelf” variety is processed cadaveric bone or a synthetic bone. The most common used is the cadaveric bone as it is readily available and safe. The synthetic bone can be used in situations not requiring immediate structural support.
Case 1 – Loosening
When possible, only the loose part of the joint is removed and replaced. Since the knee replacement is basically comprised of the femoral and tibial components only the loose component will be revised. However, sometimes the implants are so old; the implant that is not loose can not be matched with the new component that will replace the loose one. In this case, both components are removed and replaced.
Case 2 – Wear without loosening
In the case of a worn bearing, only the plastic (polyethylene) insert will be exchanged. Sometimes there can be substantial osteolysis in the face of implants that are not loose. This requires bone grafting in addition to replacing the polyethylene insert.
Case 3 – Knee cap dislocation
Sometimes the knee cap dislocates or does not track well and will not become stable without surgery. This problem can be solved by multiple different methods. Surgery may include moving one or all components into a better position. Stability can also be achieved by altering the surrounding soft tissue.
Case 4 – Infection
For reasons previously discussed, in the face of an infected total knee replacement, the implants are completely removed and cement mixed with antibiotics is placed in the joint space. The patient is then given intravenous antibiotics for a minimum of six weeks. A month after the cessation of antibiotics, an aspiration of the joint is performed to assure the joint is bacteria free. Once the infection is completely gone, new knee prostheses can be implanted.
Front and side view x-rays showing a failed total knee replacement. The bottom component (tibia) is loose and angulated.
Front and side view x-rays showing the above knee after revision surgery. The stems going up the femur and down the tibia enhance stability of the implant.