During primary total knee replacement, the knee joint is replaced with an implant, or prosthesis, made of metal and plastic components. Although most total knee replacements are very successful, over time problems such as implant wear and loosening may require a revision procedure to replace the original components.
There are different types of revision surgery. In some cases, only one implant or component of the prosthesis has to be revised. Other times, all three components— femoral, tibia, and patellar—need to removed or replaced and the bone around the knee needs to be rebuilt with augments (metal pieces that substitute for missing bone) or bone graft.
Damage to the bone may make it difficult for the doctor to use standard total knee implants for revision knee replacement. In most cases, he or she will use specialized implants with longer, thicker stems that fit deeper inside the bone for extra support.
(Left) In this x-ray, the primary knee replacement implant is unstable due to weakened bone. (Right) In revision surgery, components with longer stems fit more securely into the bones and provide stability.