Revision Total Knee Replacement is the replacement of the previous failed total knee prosthesis with a new prosthesis. It is a complex procedure that requires extensive preoperative planning, specialized implants and tools, prolonged operating times, and mastery of difficult surgical techniques to achieve a good result.
Wear and Loosening: Properly functioning implants depend on their appropriate fixation to the bone; fixation is usually achieved by cementing the implant onto the bone. Some surgeons prefer to use biologic (non-cemented) fixation.
Although implants are firmly fixed at the initial knee replacement surgery, they may become loose over time. Friction caused by the joint surfaces rubbing against each other wears away the surfaces of the implant, creating tiny particles that accumulate around the joint. In a process called aseptic (non-infected) loosening, the bond of the implant to the bone is destroyed by the body’s attempt to digest the wear particles. During this process, normal bone is also digested (a condition called osteolysis), which can weaken or even fracture the bone.
When the prosthesis becomes loose, the patient may experience pain, change in alignment, or instability. Aseptic loosening is the most common mode of failure of knee implants.
Infection: Infection is a devastating complication of any surgical procedure. In total knee replacement, the large foreign metal and plastic implants can serve as a surface for the bacteria to latch onto, inaccessible to antibiotics. Even if the implants remain well fixed, the pain, swelling, and drainage from the infection make the revision surgery necessary. With current surgical techniques and antibiotic regimens, the risk of infection from total knee replacement is less than 1%.
Revision surgery of the infected knee takes several forms. Depending on the degree of infection and damage, the decision is made to either perform a simple washout of the knee with component retention or complete exchange of the implants.
In most cases of infected TKR, two separate operations are required: first to remove the old prosthesis and insert a block of cement with antibiotics (known as an antibiotic-impregnated cement spacer) and a second surgery to remove the spacer and insert a new prosthesis. Intravenous antibiotics are given during this period to eradicate the infection.
Fractures: The type and extent of the fracture will determine if revision surgery is needed. Periprosthetic fractures (fractures around the knee implants) that disrupt the fixation or the stability of the implant may require revision surgery.
Instability: Instability occurs when the soft-tissue structures around the knee are unable to provide the stability necessary for adequate function during standing or walking. Instability may be the result of increased soft-tissue laxity (looseness), inadequate flexion of the implants, or improper positioning or alignment of the prosthesis. Pain or a sense of “giving away” of the knee may alter knee function and require revision surgery.
Patient-Related Factors: Age, activity level, surgical history, and weight can contribute to implant failure. Younger, more active patients have a higher rate of revision than older, less active patients. Obese patients have a higher incidence of wear and loosening. Patients with previous knee surgeries are at higher risk for infection and implant failure.
A failed knee implant is usually indicated by an increase in pain or a decrease in knee function. Persistent pain and swelling can indicate loosening, wear, or infection, and the location of the pain can be all over the knee (generalized) or in one particular area (localized).
The decline in knee function may result in a limp, stiffness, or instability. Patients who demonstrate these symptoms and signs may require revision joint surgery.