Although today’s implants are designed to last many years, it’s possible that at some point in the future—typically 15 to 20 years or more—your prosthetic will break or wear out. If you are overweight or you engage in high impact activities such as running or court sports, the device may fail sooner. When a knee replacement no longer functions correctly, revision surgery is often required. During this procedure, a surgeon replaces the old device with a new one.
Revision surgery isn’t something to take lightly. It is more complicated than a primary (or "initial") total knee replacement (TKR) and entails many of the same risks. Nevertheless, more than 54,000 knee revision operations are performed in the U.S. each year. It’s estimated that over half of these procedures take place within two years of the initial knee replacement.
Why Revision Surgery is More Complicated Than Initial Surgery
It’s important to note that a revision knee replacement does not provide the same lifespan as the initial replacement (usually about 10 years rather than 20). The accumulated trauma, scar tissue, and mechanical breakdown of components lead to diminished performance. Revisions are also more susceptible to complications.
A revision procedure is typically more complex than the original knee replacement surgery because the surgeon must remove the original implant, which would have grown into the existing bone. In addition, once the surgeon removes the prosthesis, there is less bone remaining. In some instances, a bone graft—transplanting a piece of bone transplanted from another part of the body or from a donor—might be required to support the new prosthesis. A bone graft adds support and encourages new bone growth. However, the procedure requires additional preoperative planning, specialized tools, and greater surgical skill. The surgery takes longer to perform than a primary initial knee replacement.
If a revision surgery is necessary, you will experience specific signs. Indications of excessive wear or failure include: diminished stability and/or reduced function in the knee; increased pain or an infection (which usually occurs soon after the initial procedure); or a bone fracture or outright device failure. In other cases, bits and pieces of the prosthetic device may break off and cause tiny particles to accumulate around the joint.
Reasons for a Revision
Short-term revisions—Infection, implant loosening from failed procedure or a mechanical failure.
An infection will usually present itself within days or weeks of surgery. However, infection can also occur many years after surgery. The complication rate for surgery due specifically to mechanical failure of the implant is 0.7 percent according to the Center of Medicare and Medicaid Services (CMS). However, CMS data also indicates that the average rate of revision surgery within 90 days is only 0.2 percent; within 18 months, the rate jumps to approximately 3.7 percent.
Infection following knee replacement can cause severe complications. It is generally caused by bacteria that settle within around the wound or within the device. Infection can be introduced by contaminated instruments or by people or other items within the operating room. Fortunately, because of extreme precautions taken in the operating room infection occurs less than two percent of the time. However, if an infection takes place, it can lead to a buildup of fluids and potentially a revision.
If you notice any unusual swelling, tenderness or fluid leakage, contact your surgeon immediately. If your surgeon suspects that there’s a problem with your existing artificial knee, you will be asked to undergo an examination and assessment. This involves X-rays and possibly other imaging diagnostics such as a CT scan or Magnetic Resonance Imaging (MRI). The latter can provide important clues about bone loss and determine whether you are a suitable candidate for a revision.
Patients that experience fluid buildup around the knee usually undergo an aspiration procedure to remove the fluid. The doctor sends the fluid to a lab to determine the type of infection and whether a revision surgery or other treatment steps are in order.
Long-term revisions—Pain, stiffness, loosening due to wear of mechanical components, dislocation.
Long-term wear and loosening of the implant can occur over years.
Various sources have published statistics on the long-term revision rates for knee replacement. According to the U.S. Department of Health and Human Services Agency for Healthcare Research and Quality (AHRQ), and by observing TKR patients over an eight year period ending in 2003, the long-term revision rate is 2 percent for five or more years. Based on a meta-analysis of worldwide joint registry databases, published in the Journal of Bone & Joint Surgery in 2011, the revision rate is 6 percent after five years and 12 percent after ten years. Healthline’s analysis of approximately 1.8 million Medicare and private pay records, the rate of revision for all age groups within five years from surgery is about 7.7 percent. The rate increases to 10 percent for patients aged sixty-five and older.
The data on long-term revision rates varies and depends on numerous factors, including the ages of the patients observed. The chances for a revision are lower for younger patients. You can reduce future problems by maintaining your weight and avoiding activities that place undue stress on the joint, such as running, jumping, court sports, and high impact aerobics.
During a process called aseptic loosening the bond between the bone and the implant breaks down as the body attempts to digest the particles. When this event takes place, the body also begins to digest bone—a process called osteolysis. This can lead to a weakened bone, fracture, or problems with the original implant. Aseptic loosening doesn’t involve an infection.
Typically, a revision involves two separate operations: Initially, the orthopedist removes the old prosthesis and inserts a polyethylene and cement block known as a spacer that has been treated with antibiotics. During the second procedure, the surgeon removes the spacer, reshapes and resurfaces the knee, and then implants the new knee device. The two procedures usually take place about six weeks apart. Inserting the new device typically requires 2-3 hours in surgery, compared to 1½ hours for a primary knee replacement.
If you require a bone graft, the surgeon will either take bone from another part of your own body or use bone from a donor, usually obtained through a bone bank. The surgeon might also install metal pieces such as wedges, wires, or screws to reinforce the bone for the implant or fasten the implant to the bone. A revision requires the surgeon to use a specialized prosthetic device.
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Knee Revision Surgery Complications
Complications that may follow knee revision surgery are similar to those for knee replacement. They include:
- Deep vein thrombosis.
- Infection in the new implant
- Implant loosening. Overweight patients are at higher risk.
- Dislocation of the new implant. The risk of dislocation is twice as high for revision surgery as for a primary knee replacement.
- Additional or more rapid loss of bone tissue.
- Bone fractures during the operation that could occur if the surgeon must use force or pressure to remove the old implant.
- Difference in leg length resulting from shortening of the leg with the new prosthesis.
- Formation of heterotopic bone, which is bone that develops at the lower end of the femur following surgery. Joint infections after surgery put patients at increased risk.
Morbidity and Mortality Rates
As with primary knee replacement, the 30-day mortality rate following knee revision surgery is low, between 0.1 percent and 0.2 percent. The estimated complications rates are:
- deep venous thrombosis: 1.5 percent
- deep infection: 0.97 percent
- loosening of the new prosthesis: 10–15 percent
- dislocation of the new prosthesis: 2–5 percent
Recovery and Rehabilitation
Afterwards, you will undergo a similar recovery and rehabilitation process as someone who receives a primary knee replacement. This includes medication, physical therapy, and the administration of blood thinners to prevent clots. You will initially require an assistive walking device such as a cane, crutches, or walker and you will likely be in physical therapy for three months or longer. As with the original knee replacement, it is important to stand and walk as quickly as possible. Pressure, compression, or resistance is needed for the bone to grow and properly bond with the implant.
The length of recovery after revision knee surgery varies in comparison to a patient's first knee replacement. Some individuals take longer to recover from revision surgery while others recover more rapidly and experience less discomfort than during the initial TKR.
Various studies indicate that about 80 percent of patients that undergo a revision surgery experience excellent results. However, about 20 percent of patients report some ongoing pain following the revision. In extreme cases—when another knee replacement isn’t advisable—an alternative procedure such as arthrodesis (knee fusion) might be used to relieve pain.
If you think you may require a revision, speak to your doctor and review your condition to understand whether you’re a good candidate for the surgery.