Symptoms of Infection After Hip or Knee Replacement

In the days and weeks following your surgery, watch for symptoms that include:

  • fevers (more than 101F),
  • chills,
  • excessive redness (cellulitis),
  • opening wound edges,
  • prolonged or excessive wound drainage,
  • cloudy wound drainage, and
  • foul smells.

Normal symptoms after hip or knee replacement include a slight redness and warmth around the joint as well as bruising or ecchymosis. 

At the University of Utah Center for Hip and Knee Reconstruction, we use a waterproof (occlusive) dressing that is impregnated with silver ions. This dressing has been shown to help reduce the chances of infection. You may notice some slight spotting on the dressing, but excessive drainage into that dressing should be reported to your doctor.

Long after a joint replacement has healed, if you have increases in pain, fevers, chills, swelling, redness, warmth, pain when you move the joint, or difficulty putting weight on the hip or knee, you should discuss this with your doctor.

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Hip or Knee Replacements Infection Statistics

Infection is a rare, but serious complication after total joint replacement surgery. It occurs in one ot three percent of patients nationally; though, our most recent review of infection data at the University of Utah Center for Hip and Knee Reconstruction showed an infection rate better than the national average at 0.5 percent (as of 2013).

Joint Infection Causes

Infections generally occur due to bacteria that live on/in/around us. All of us have bacteria that live on our skin, in our nose, and in our intestines. During surgery, we clean the skin and maintain a sterile environment around the surgical site to remove bacteria from the area.

Patients also receive antibiotics immediately before and for 24 hours after surgery. However, bacteria can find their way in through a surgical incision. Bacteria can also get to a surgical site through the blood stream.

Infections can occur soon after surgery, but can also occur days, months, weeks, years, and even decades after a joint replacement surgery.

Invasive procedures (procedures throught the skin) around the time of a joint replacement also increase the risk of infection. You should have these proceures—such as a biopsy, Moh’s surgery for skin cancer, or colonoscopy—six weeks before your surgery date.

Dental Cleaning & Procedures

Dental cleaning, especially root canals, extraction, and crowns, need to be taken care of six weeks before surgery or six to twelve months after surgery.

Why Is Infection So Bad in Hip or Knee Replacement?

The metal and plastic parts used in joint replacements do not have an immune system. So, unlike other infections our bodies can clear with an antibiotic or on their own, infected joint replacements will remain infected without surgery.

If we identify infection early, we may be able to treat it by a surgery to simply wash the joint out. However, bacteria create films that coat the implants and surrounding tissues that can make getting rid of them difficult, if not impossible.

The longer the infection is present, the less likely we can remove the bacteria by a simple washout surgery. In these cases, the surgery becomes more complicated, and the implants have to be removed.

Other Ways Joints Become Infected

Following joint replacement surgery, the blood flow to the joint increases for a period of time, as the body is healing. Along with the metal and plastic parts, which have no immune system, this increased blood flow can carry bacteria from the blood stream to the replaced joint. If the bacteria reach the implants, they may stick and create an infected joint.

Bacteria can be carried by our blood stream because of severe illnesses, such as sepsis. However, more commonly, bacteria may transiently get carried through the blood, and the body clears it without any obvious illness, unless it gets carried to the replaced joint. This is why infections can occur in replaced joints even decades after the surgery.

If you get a bacterial infection in the body, it is a good idea to see your primary care doctor. Colds, flus, or other viral infections do not require antibiotics. However, if you get a cut that looks worrisome or a redness in the legs or urinary infections or other bacterial infections in the body, your primary care doctor may need to treat these with antibiotics.

Certain medical procedures can increase the risk of pushing bacteria into the blood stream, such as dental work, abdominal surgery, or colorectal procedures. It is important to take antibiotics prior to these procedures.

Treating Infections in Hip or Knee Replacements

In the United States, the standard treatment of infection in an artificial joint is a two-stage process: 

  1. We remove all the existing implants, cleaning out the joint and surrounding soft tissues.
  2. We place a temporary artificial joint.

We often place this temporary joint with a high-dose antibiotic to deliver antibiotics locally to the surrounding joint tissues.

Removing the existing joint does have some risks. Each time a joint replacement is revised and/or removed, you lose bone and your tissues are also affected. You can decrease risk by finding an expert surgeon.

After these types of surgeries, you can often be mobile, but you will have to be careful how much weight you place on the joint. You may only be able to put 50 percent of your weight on the leg/knee/hip for weeks or months afterwards.

Along with the surgery to treat the infection, we also often use systemic antibiotics. Frequently we use two to six weeks of intravenous (IV) antibiotics to target the infection. Patients have a large IV line called a PICC line placed to receive these antibiotics. We check the effects of the antibiotics regularly through labs to monitor the effects of the antibiotics on the body and the body’s response to the treatment.

We use a few tests, such as ESR and CRP, which are markers of inflammation, to see if the treatments are successful. Lower numbers are good and suggest a response to the treatment. Numbers that stay high or are increasing are a concern. If we see numbers that stay high or increase, we often perform more tests, such as an aspiration of the joint.

Recovery Time

In total, the treatment for an infection after joint replacement can take six months of recovery time. Antibiotics may be given for six to eight weeks via IV and possibly three to six months. Potentially, you may even take antibiotics by mouth for your lifetime.

Factors in Treating the Infection

Several factors are involved in successfully treating an infected joint replacement, such as the:

  • type of bacteria involved in the infection,
  • the duration of the infection, and
  • the health status of the patient.

Resistant organisms (MRSA for example) are harder to treat. Patients with weakened immune systems, diabetes, and morbid obesity are at risk to get infections and may have more trouble with the treatments.

Infections that have been present for a longer period of time are typically more difficult to treat. Soft tissue complications, such as chronic wound drainage or deficiencies in soft tissues that require additional procedures, are also higher risk for failure.

Success rates reported in studies range from less than 40 percent to 100 percent depending on the type of infection and treatments. On average, success rates are between 80 to 90 percent for the treatment of long-standing infections with the use of the two-staged procedure.

Who Is at Risk for Artificial Joint Infection?

As mentioned above, these infections are rare. Not everyone will get them. However, certain patients are at higher risk than others.

Highest Risk Factors

The greatest risk factors for infection are:

  • obesity,
  • poorly controlled diabetes, and
  • smoking.

Some of these are modifiable risk factors, though, meaning you can decrease your risk by improving these conditions.

To measure your body fat (and possible obesity) based on your height and weight, calculate your body mass index (BMI) using a BMI calculator.

Other Risk Factors

There are other risk factors for infection. Patients with prior surgeries at a surgical site have scar tissue and altered tissue planes that may delay healing and lead to infection. Patients that have a history of prior infections are also at increased risk. Poor nutrition, anemia, liver disease, kidney disease, or other health issues are also risk factors.

Finally, patients who have certain bacteria that live on them routinely, such as resistant staph (MRSA), may be able to decrease their infection risk by identification through screening and subsequent decolonization (see below).

*Note: The American Association of Orthopaedic (AAOS) updated their recommendations in 2016. Our surgeons' interpretation of these guidelines is that patients with a joint replacement at "high risk for infection" should take antiobiotics before dental work and invasive procedures through their life.

Examples of patients considered high risk are those with the following medical problems:

  • Uncontrolled diabetes (A1C>8, glucose>200)
  • Compromised immune system: HIV/AIDS, rheumatoid arthritis, or patient on oral steroids, active cancer, prior organ transplant or bone marrow translant
  • History of periprosthetic or deep prosthetic joint infection

Screening Tests

We screen all patients undergoing joint replacement surgery for their nutrition status, bacterial colonization, kidney and liver function, protein status, and for the possibility of anemia. All patients receive these tests because we can’t predict who may have some of these issues that they or their primary care doctors were unaware of.

Given the significance of infection after joint replacement, all patients are considered to be at risk. We try to minimize the risk of complications by identifying patients at risk and optimizing their health status before they undergo the surgery.

Minimize Your Risk of Joint Infection

The best ways to minimize the risk of infection after joint replacement is by being healthy. We have described above some of the risk factors. Optimize your health status by doing some of the following:

Obesity

Reducing your weight before surgery can help minimize the risks with obesity. You can modify your diet and exercise; though, while exercise if often recommended as the best means to reduce weight, it can be very difficult, especially in patients with pain due to arthritis.

We recommend water therapy, swimming, cycling, and elliptical machines as high aerobic activities with low impact.

University of Utah Health also offers bariatrics services that may be able to offer additional information on weight reduction methods, including surgical options.

Diabetes

You can manage diabetes can by adjusting:

  • diet,
  • exercise, and
  • medications.

HbA1c, which is a marker of average glycemic control over three months’ time, is a reasonable indicator of diabetic control. We often require that HbA1c numbers be less than seven percent before surgery.

The greatest risk factor you can modify before surgery is glycemic control. Poorly controlled glucoses inhibit the immune system and healing response and increase the risk of infection dramatically. So, even if we get the HbA1c controlled well, it is just as important to maintain good control (with glucoses less than 120) when at all possible.

Smoking

Smoking is bad for the body’s blood flow. One cigarette, for example, has enough nicotine to constrict the tiny blood vessels that are responsible for helping the surgical site to heal for up to six hours at a time. As such, you must stop smoking around the time of surgery.

At University of Utah Health, we recommend quitting at least four weeks before surgery, as quitting closer to the time of surgery leads to coughs and other respiratory issues that put the patient at risk for other complications around the time of surgery. Also, you should stop all nicotine products around the time of surgery.

Because the healing process after a joint replacement can last months and even years, we recommend stopping smoking all together. We realize that not all patients, however, can stop smoking, so we recommend waiting until at least six weeks after surgery to start again.

Malnutrition & Anemia

Patients may not know they are malnourished or anemic. Even high endurance athletes or morbidly obese patients may show evidence of malnutrition, low protein, and the like. Screening labs help identify these issues, and we may recommend supplements or medical treatments before joint replacement surgery.

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