Revision Knee Replacements
Why Do Knee Replacements Fail?
The most common reasons why knee replacements may fail include:
- Instability: Instability occurs when the supporting soft tissues have failed and are unable to function properly.
- Loosening: Most knee replacements are held in place by cement. However, the knee implants can become loose over time and cause destruction of the bone and tissue.
- Infection: After knee replacement surgery, it is possible to develop an infection. This occurs when bacteria latches onto the knee implants and cause an infection.
Additional reasons for revision knee replacements include stiffness, fracture, wearing out of the plastic, and osteolysis (resorption of bone). The workup, preoperative course, expected outcomes and recovery vary greatly based on the reason for revision. An overview of the most common reasons for revision knee replacement is addressed below.
Revision Knee Replacement for Instability
Instability following total knee replacement is a common cause for knee revision surgery. For a knee replacement to function properly there must be normal soft tissue (ligament) integrity as well as proper placement, alignment, sizing, and rotation of the knee replacement components. If either of these factors is lacking, patients may experience symptoms of instability.
Symptoms: Symptoms of instability after total knee replacement include swelling, pain, sense of “not trusting” the knee, and difficulty going up and down stairs. These symptoms may worsen with time.
Workup: Workup for instability includes a thorough patient history, physical exam, and x-rays. Typically, instability can be diagnosed with these procedures alone. However, your surgeon may order additional tests to ensure there are no other processes going on such as infection or loosening of the components.
Treatment: Non-operative treatments can include physical therapy, bracing, anti-inflammatory pills, topical anti-inflammatory agents, and activity modifications. If these treatments are not effective, surgery may be an option. The surgical treatment for instability requires revision (exchange) of one or more of the knee replacement components. Talk to your surgeon about which approach would be required on an individual basis.
Outcomes: The large majority of patients who undergo knee revision surgery for instability will gain significant improvement in pain, stability, and knee function.
Revision Knee Replacement for a Loose Knee Replacement
Most knee replacements in the United States are held in place with bone cement. This allows for immediate fixation, weight-bearing, and function. However, it is possible for this cement bond to loosen over time.
Symptoms: Symptoms of a loose knee replacement include pain (particularly when putting weight on the knee) and swelling. Since loosening is the sort of problem that takes time to develop, these symptoms typically develop gradually in a knee that may have been functioning well for many years.
Workup: A loose knee replacement can typically be diagnosed based on simple x-rays. Occasionally, more advanced imaging tests such as a bone scan may be required. If loosening is present, your surgeon will likely also test for infection, as infection is a potential cause for component loosening, and the treatment options are significantly different if infection is present.
Treatment: The treatment for component loosening is revision surgery. If loose components are left in place, they will continue to become more painful and can lead to destruction of the bone and soft tissues. At the time of revision, the loose component is removed and a new component is placed, typically using longer stems or other methods of augmentation to help make the implant more stable. In some instances, it is necessary to change all of the components (not just the one that is loose) in order to achieve a properly functioning knee.
Outcomes: While revision surgery is never easy, the outcomes of knee revision replacement for loosening are very good. It is possible for revision implants to loosen over time as well, but newer technology and techniques are making this less of a problem.
Revision Knee Replacement for Infection
Infection after knee replacement is one of the most dreaded complications. It can be successfully treated in most patients, but it is a long and difficult process. The treatment and expected outcomes depend on multiple factors such as: overall patient health, type of infecting organism, duration of the infection, and the degree of associated damage to the bone and soft tissues around the knee.
Symptoms: Symptoms of infection after knee replacement include pain (either chronic persisting pain or a dramatic increase in pain), fevers, chills, redness, drainage, and swelling. Some infections are subtle and low-grade and can be mildly symptomatic over a prolonged period. Other infections come on suddenly and are associated with significant sickness and dramatic symptoms.
Workup: Apart from the basic evaluation and x-rays, workup for infection includes blood work and drawing fluid from the knee. Blood work includes a Sedimentation rate (SED rate) and C-Reactive protein (CRP). These labs are typically elevated if there is an infection but may be elevated for multiple other reasons as well. However, if these labs are normal, the likelihood of infection is low (though still possible). Your surgeon may also choose to aspirate fluid from the knee. This fluid can be cultured to see if any bacteria grow and can also be analyzed to determine how many white blood cells are present. Promising new tests are becoming developed to assist with diagnosing subtle infections, and will likely play a much larger role with diagnosing infection in the future.
Treatment: The treatment for infection needs to be individualized based on many different important considerations. There is no “one size fits all” treatment for infection. Non-operative treatment is very rare, typically only reserved for patients too frail to undergo surgery. From a surgical standpoint, there are two general approaches: irrigation and debridement (I&D) of the knee while keeping the components, and 2-stage revision.
Irrigation & Debridement (I&D): I&D of the knee may be recommended if symptoms have been present for only a short period of time, the original knee replacement was very recent, or knee implants are too complex to safely remove. With this approach, patients generally receive IV antibiotics for several weeks, and then may be transitioned to an oral antibiotic long-term to help keep any infection from coming back.
2-Stage Revision: In many circumstances, it is necessary to remove all of the foreign material from the knee for a time to fully eradicate the infection. This is because bacteria are able to form a biofilm (or microscopic slime layer) on foreign material that cannot be fully treated with antibiotics or simple washing alone. The term “2-stage” refers to the fact that this process generally requires two separate surgeries. The first surgery is to remove all foreign material, thoroughly clean the knee, and implant a spacer which delivers high dose antibiotics to treat the infection from within the knee. Patients then receive IV antibiotics for several weeks. If the infection is successfully eradicated, the second surgery can be performed which involves removal of the antibiotic spacer and placement of new knee replacement parts. In reality, sometimes multiple surgeries may be necessary before the infection is eradicated. While a 2-stage process is the best chance at curing infected knee replacements, it is a long and difficult process.
Outcomes: Reported success rates range anywhere from <50% success to 90% success. Again, outcomes have a lot to do with factors such as overall patient health, type of infecting organism, duration of the infection, the degree of associated damage to the bone and soft tissues around the knee, and the treatment protocol selected.
Why should I have my revision knee replacement done at ROC?
At ROC, we have the most comprehensive team of expert knee surgeons in northern Nevada. This allows us to provide our patients with expert care, from non-operative treatments to revision of even the most complex cases. Our surgeons’ experience and dedicated focus allows them to combine cutting edge technology with tried and true principles to give patients the best chance at an excellent outcome. If you think you may need a revision knee replacement, contact us to schedule a consultation.