Here’s what you need to know about infections after knee or hip replacement surgery

Pre-operative measures to prevent infections

Before a knee or hip replacement surgery, we do several things to try and reduce a patient’s risk of developing an infection.

• We give patients antibacterial soap to wash with in the days before their surgery.
• Patients who have lost a significant amount of weight before surgery and are in a calory deficit have a higher likelihood of infection. We make sure that our patients have been eating a balanced diet so that they don’t have surgery while they are in a catabolic state.
• We take swabs and urine cultures before surgery to check that patients don’t have an existing infection.
• 30 minutes before surgery, patients are started on antibiotics.

Post-operative measures to prevent infections

It is important for a patient to follow their healthcare team’s instructions post-surgery: Take antibiotics and pain medicine as directed and stick to the rehabilitation programme.

Wound care is critically important after surgery. If there is a problem with a wound, patients must please contact their orthopaedic surgeon or the hospital where they were treated, rather than their doctor. If a patient does go to a GP and they give them antibiotics, it can affect our ability to identify what type of infection the patient has if they land up coming to us later on.

Being vitamin D deficient increases a patient’s risk of infection. After the operation, we ask our patients to take vitamin supplements, including vitamin D, to support their immune system during this stressful time and reduce your risk of infection.

How to diagnose an infection

There are several indications that a patient may have an infection. Symptoms of an infection are typically:

• Raised inflammatory markers (shown with blood tests)
• Increased pain, stiffness or swelling in a joint that was functioning well
• Warmth around the wound
• Redness around the wound
• Pus, blood or other fluids coming out of the wound
• Fever

It is important to remember that some warmth and swelling is normal and can last for several months after joint replacement surgery.

• Read this article for more information about what symptoms you can expect after knee or hip replacement surgery and how to tell what’s normal and what isn’t.

If a patient is concerned about their symptoms or any aspect of their recovery, they must please contact their care team.

What is an early infection?

Early-stage infections usually occur within the six weeks post-surgery. When it comes to preventing early-stage infections, wound healing is crucial. If a patient’s wound heals properly, their chance of developing an early-stage infection is slim (however, this does not exclude them from getting an infection later on).

If a patient’s wound hasn’t healed within 10 to 14 days, we will treat them for infection.

What is a late infection?

A late infection can occur months or even years after surgery. Late-stage infections occur when bacteria enters the body through cuts in the skin, wounds from other surgical procedures, or during major dental procedures (like root canal). The bacteria can travel through the body and infect the area around the joint. People who have compromised immune systems are at higher risk of developing infections after a joint replacement.

Patients who develop a late-stage infection will often find that their wound, after healing properly, suddenly has lots of pus or other fluids coming out of it.

How infections are treated

We send some of their blood and aspirate fluid (if there is any around the implant) to test for infection. We will also take the patient back to theatre for a DAIR procedure. DAIR stands for debridement, antibiotics, and implant retention.

During the procedure we wash out the area around the implant, do a thorough debridement (removing dead, damaged or infected tissue), take cultures for testing, and replace any movable parts that are easy to replace.

The patient will be given a broad-spectrum antibiotic after the procedure and kept in hospital. We will need to wait until the cultures we took in theatre grow an organism so that we know what type of infection they have. It could take anything from 48 hours to 14 days for the cultures to grow.

If the patient’s cultures do grow an organism, we can treat them with narrow spectrum antibiotics that target the specific bacteria that caused their infection. Fortunately, there is a high success rate of becoming infection free with this approach.

While the patient is in hospital, as we wait for their cultures to grow, they will continue to be monitored. Their inflammatory markers will be checked regularly to see if they are decreasing, and their wound will be monitored to see if it is healing. If their inflammatory markers do not reduce or their wound doesn’t heal, they will need to go into theatre again for another DAIR procedure.

If a patient’s cultures show that their infection is caused by a very aggressive or drug-resistant bacteria, we may need to remove their implants. If this happens, we will put temporary cement spacers in place of the implant and treat them with narrow spectrum antibiotics. Six weeks later, we will remove the spacers and insert a new implant. After that the patient will continue on antibiotics for around another six weeks.

Treatment is a team effort

If a patient develops an infection after knee or hip replacement surgery, it’s important that their orthopaedic surgeon works with a multidisciplinary team to treat and manage them. This team could include a nutritionist and pathologists. The surgeon may also consult with other orthopaedic surgeons to make sure they are taking the best possible approach in treating the infection.

Unfortunately, if a patient has developed an infection after their joint replacement surgery, their potential to develop another infection increase. A patient who has had one or more DAIR procedures may experience discomfort indefinitely because of the scar tissue and muscle loss caused during these operations.

Knee and hip replacements remain life-changing procedures to reduce pain and restore mobility in patients. Your orthopaedic surgeon and their team will explain all the benefits and risks with you before the operation and allow you to ask questions. They will also work with you to reduce your risk of developing an infection. As always, if you have any concerns before or after surgery, please discuss them with your care team.

• Read more on what to expect after total knee replacement surgery.
• Read more on what activities are allowed after knee and hip replacement surgery.