Joint Replacement Infection
Description
Any infection in your body can spread to your joint replacement.
Infections are caused by bacteria. Although bacteria are abundant in our gastrointestinal tract and on our skin, they are usually kept in check by our immune system. For example, if bacteria make it into our bloodstream, our immune system rapidly responds and kills the invading bacteria.
However, because joint replacements are made of metal and plastic, it is difficult for the immune system to attack bacteria that make it to these implants. If bacteria gain access to the implants, they may multiply and cause an infection.
Despite antibiotics and preventive treatments, patients with infected joint replacements often require surgery to cure the infection.
Cause
A total joint may become infected during the time of surgery, or anywhere from weeks to years after the surgery.
The most common ways bacteria enter the body include:
- Through breaks and cuts in the skin
- Major dental work
- Other sites of surgery
Some people are at a higher risk for developing infections after a joint replacement procedure. Factors that increase the risk for infection include:
- Diabetes mellitis
- Immune deficiency
- Corticosteroid use
- Obesity
- Recent extreme weight loss
Symptoms
Signs and symptoms of an infected joint replacement include:
- Increased pain and stiffness in a previously well functioning joint replacement
- Swelling
- Redness
- Wound drainage
- Fevers and shivers
- Fatigue
Clinical Examination
When total joint infection is suspected, early diagnosis and proper treatment increase the chances that the implants can be retained. Your doctor will discuss your medical history and conduct a detailed physical examination.
Tests
Imaging tests. X-rays and bone scans can help your doctor determine whether there is an infection in the implants.
Laboratory tests. Specific blood tests can help identify an infection. For example, in addition to routine blood tests like a complete blood count (CBC), your surgeon will likely order two blood tests that measure inflammation in your body. These are the C-reactive Protein (CRP) and the Erythrocyte Sedimentation Rate (ESR). Although neither test will confirm the presence of infection, if either or both of them are elevated, it raises the suspicion that an infection may be present. If the results of these tests are normal, it is unlikely that your joint is infected.
Additionally, your doctor will analyze fluid from your joint to help identify an infection. To do this, he or she uses a needle to draw fluid from your hip or knee. The fluid is examined under a microscope for the presence of bacteria and is sent to a laboratory. There, it is monitored to see if bacteria or fungus grow from the fluid.
The fluid is also analyzed for the presence of white blood cells. In normal hip or knee fluid, there are a low number of white blood cells. The presence of a large number of white blood cells (particularly cells called neutrophils) indicates that the joint may be infected. The fluid may also be tested for specific proteins that are known to be present in the setting of an infection.
Treatment
Nonsurgical Treatment
In some cases, just the skin and soft tissues around the joint are infected, and the infection has not spread deep into the artificial joint itself. This is called a “superficial infection.” If the infection is caught early, your doctor may prescribe intravenous (IV) or oral antibiotics.
This treatment has a good success rate for early superficial infections.
Surgical Treatment
Infections that go beyond the superficial tissues and gain deep access to the artificial joint almost always require surgical treatment.
Debridement. Deep infections that are caught early (within several days of their onset), and those that occur within weeks of the original surgery, may sometimes be cured with a surgical washout of the joint. During this procedure, called debridement, the surgeon removes all contaminated soft tissues. The implant is thoroughly cleaned, and plastic liners or spacers are replaced. After the procedure, intravenous (IV) antibiotics will be prescribed for approximately 6 weeks.
Staged surgery. In general, the longer the infection has been present, the harder it is to cure without removing the implant.
Late infections (those that occur months to years after the joint replacement surgery) and those infections that have been present for longer periods of time almost always require a staged surgery.
The first stage of this treatment includes:
An antibiotic spacer is a device placed into the joint to maintain normal joint space and alignment. It also provides patient comfort and mobility while the infection is being treated.
Spacers are made with bone cement that is loaded with antibiotics. The antibiotics flow into the joint and surrounding tissues and, over time, help to eliminate the infection.
Patients who undergo staged surgery typically need at least 6 weeks of IV antibiotics, or possibly more, before a new joint replacement can be implanted. Orthopaedic surgeons work closely with other doctors who specialize in infectious disease. These infectious disease doctors help determine which antibiotic(s) you will be on, whether they will be intravenous (IV) or oral, and the duration of therapy. They will also obtain periodic blood work to evaluate the effectiveness of the antibiotic treatment.
Once your orthopaedic surgeon and the infectious disease doctor determine that the infection has been cured (this usually takes at least 6 weeks), you will be a candidate for a new total hip or knee implant (called a revision surgery). This second procedure is stage 2 of treatment for joint replacement infection.
During revision surgery, your surgeon will remove the antibiotic spacer, repeat the washout of the joint, and implant new total knee or hip components.
Single-stage surgery. In this procedure, the implants are removed, the joint is washed out (debrided), and new implants are placed all in one stage. Single-stage surgery is not as popular as two-stage surgery, but is gaining wider acceptance as a method for treating infected total joints. Doctors continue to study the outcomes of single-stage surgery.
Adapted with permission from https://orthoinfo.aaos.org