What is Knee Revision Surgery?

The implants that work correctly depend on their adequate fixation on the bone. Fixation is generally achieved by cementing the implant to the bone. Some surgeons prefer to use biological fixation, which means that no cement is placed between the implant and the bone. Although implants are firmly fixed in the initial knee replacement surgery, they can loosen over time. The cause of loosening may not always be clear, but high-impact activities, excessive body weight, and wear on the polyethylene component can all act as contributing factors. The friction caused by the joint surfaces rubbing against each other wears down the implant surfaces, creating small particles that accumulate around the joint. The body's attempt to digest these wear particles destroys the implant's connection to the bone in a process known as aseptic loosening (not infected). During this process, normal, healthy 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, alignment changes, or instability.

With current surgical techniques and antibiotic regimens, the risk of infection from a total knee replacement is less than 1%. However, when it does occur, infection is a devastating complication of any surgical procedure. In a total knee replacement, large metal and plastic implants can serve as a surface for bacteria to adhere to, a process known as biofilm formation. The location of these bacteria makes them inaccessible to antibiotics. Even if the implants remain securely attached, revision surgery is necessary to stop the pain, swelling, and drainage of the infection.
Revision surgery for the infected knee can take several forms. Depending on the degree of infection and damage, the surgeon will determine one of two basic courses of action:

• Perform a simple knee wash while keeping the original prosthetic components in place
• Replace the implants completely with new ones in a complete revision operation of the knee.

A full infection check will involve a one or two-stage operation, depending on the severity of the infection and the virulence of the bacteria. In the single-stage operation, the previously infected components are removed as part of a full debridement, the knee is thoroughly cleaned, and the new revision components are placed in a surgical setting (i.e., same day). In the two-stage operation, two separate operations are performed weeks apart: the first operation is to remove the old prosthesis and insert a cement block with antibiotics (known as an antibiotic-impregnated cement spacer). The second surgery consists of removing the spacer and inserting a new prosthesis. Intravenous antibiotics are given frequently during both options to eradicate the infection.

Instability occurs when the soft tissue structures around the knee cannot provide the stability necessary for proper function when standing or walking. Increased soft tissue laxity (slack) or incorrect placement or alignment of the prosthesis can cause instability. The soft tissues, including the ligaments around the knee, may stretch after surgery and no longer provide the support that the knee needs. Pain and/or the feeling of the knee "giving in" can affect knee function. If these symptoms cannot be successfully treated by non-surgical means, such as the use of braces or physical therapy, revision surgery may be required.

The type and extent of the fracture will determine whether revision surgery is necessary. Revision surgery may be required if periprosthetic fractures (fractures around knee implants) compromise implant fixation or stability.

In some cases, a total knee replacement may not allow you to achieve the range of motion necessary to perform your daily activities. This can happen if excess scar tissue builds up around the knee, preventing the joint from fully moving. When this occurs, some patients may benefit from manipulating the knee under anesthesia. For this procedure, the patient returns to the operating room and the surgeon uses his or her hands to physically flex and straighten the knee to help it regain flexibility. If excess scar tissue has accumulated around the knee joint and has significantly impaired movement and has not been very successful with manipulation, revision surgery may be considered to allow you to regain movement to perform your daily activities.

First, the old implant is removed and, if necessary, bone grafts are used to fill in the gaps where the bone has deteriorated. Then the new prosthesis is placed. The majority of revision total knee replacement surgeries take longer than original procedures (about two to three hours).

After a primary knee replacement, the postoperative treatment is quite similar. Physical therapy, blood management, pain medications as needed, antibiotics, and some form of blood clot prevention are all included. A brace or splint may be used to protect the joint after surgery.

Physical rehabilitation can begin within 24 hours after the surgery and last up to three months in most situations. Some patients take longer to recover. In some cases, a protective weight-bearing or limiting the knee's range of motion is needed to promote proper healing. Therapy will generally continue for up to three months after surgery. Assistive devices, such as a walker or crutches, will be used early in the convalescent period, and patients will switch to using a cane or walking without any assistance as their condition improves.

Most patients who undergo revision procedures can expect good to excellent results. Although pain reduction and improved stability and function are predicted outcomes, full pain relief, and function restoration are not always feasible. Up to 20% of patients may still experience some pain after revision knee surgery. This can persist for several years after the procedure. In addition, recovery after revision total knee surgery is highly dependent on the condition and function of the knee before revision surgery.

Alternatives to revision knee surgery are rarely used, as they can sometimes be more complex and give worse results than revision surgery, but include fusion or amputation of the knee. The following alternatives are used depending on the severity of the problem affecting the knee:

• Arthrodesis (fusion) of the knee joint can relieve pain but at the expense of keeping the knee in a fixed position without flexion.
• Amputation can be used in extreme cases where the knee joint has a severe infection that cannot be eradicated.