Periprosthetic joint infection (PJI)

My name is Herrick Siegel. I joined the faculty 17 years ago and specialize in orthopaedic oncology and total joint reconstruction. My practice consists primarily of complex joint revisions, tumors and infection-related cases.

A periprosthetic joint infection involves a joint, such as a hip joint or knee joint, that’s been replaced, likely containing metal that’s become colonized with bacteria. The joint becomes symptomatic and generally results in swelling, pain and morbidity in patients, and in some cases, mortality.

It is caused from either bacterium, such as staphylococcus aureus and pseudomonas aeruginosa, or a fungus. Where the infection occurs can vary from during the surgery, to the perioperative period, to much later seeding from another infection. If a patient has a cut on his foot that gets infected, it can certainly potentially seed an implanted joint.

The signs and symptoms of periprosthetic joint infection are generally related to pain. This can be in the form of swelling, possibly drainage, erythema, or warmth around the joint. Pain is a primary indicator of early joint infection.

The acute infection generally occurs in the immediate postoperative period. Generally, that’s considered to be four weeks. The difference between an acute and a chronic infection has to do with a glycocalyx that’s formed from the bacteria on the implant, which makes it very difficult to undergo treatment with antibiotics. The four-week period is generally considered acute, while delayed infections or infections that occur years after surgery are considered chronic.

It’s very important to know the pathogen, bacteria or source that is causing the infection. Cultures and molecular studies, such as PCR, can be performed to identify the organism. It is important to identify the susceptibilities of the organism, so we know what antibiotics to treat the infection with. If a resistant organism is identified, we need to modify treatment and try to improve eradication of the infection.

The acute period can be addressed with irrigation, debridement, and changing of the modular components. In the knee, the polyethylene would be removed, and in the hip, a head and liner exchange would be done. In acute PJI cases we preserve the main implants, remove those components that are modular and easy to exchange and perform a thorough debridement.

The treatment of chronic PJI is a somewhat controversial and is based more on surgeon preference. Some surgeons prefer to try to preserve implants (hip, knee etc.) at this stage through a radical debridement of the soft tissue and a thorough irrigation process. This can include Betadine in some centers, and it can include application of antibiotic substances, either in the form of powder or beads. The beads can be either biologic, so they resorb, or cement beads which are permanent.

In other situations, the implants are removed and when they are replaced is another controversial topic. They can be immediately placed back in as a one-stage operation or separated into two stages. In a two-stage operation, patients are taken to the operating room for removal of components and placement of a temporary spacer. They are then brought back at a later date, when the infection is eradicated, for re-implantation of the components.

The one-stage operation is at the same surgical anesthetic situation. The patient is brought into the operating room, components are removed, debridement is performed, and the implants are repositioned.

One and a half stages would include removal of components and a separate set of instrumentation in a different operating room. A full different setup is performed for the implant to be placed back in.

The two-stage operation is separated by a longer period of time. The components are completely removed during the initial procedure and then new components are re-implanted on a separate operating day with anesthetic.

With a PJI, irrigation and debridement are always performed followed by component removal. The different types of eradication procedures for treatment include a partial component removal, where some components are retained and only the modular components are removed, or a complete removal, where all components are removed. Infected bone may also be resected if it has been significantly impacted by osteomyelitis. That often leaves the patient with limited mobility, but a later reconstruction can be performed that will help the patient to regain their activity level.

It’s highly variable from center to center. In Europe, I believe it’s a shorter period of time between the first and second stages. In the United States, it’s somewhere between three to six months for most infections, but the time between spacer placement and re-implantation can take as long as a year.

There’s a functional risk in terms of losing mobility of the joint. There’s also a complexity of reconstructions that need to be performed due to the infection and the morbidity associated with the infection itself. Often patients will lose their employment and possibly their health insurance. It’s a very morbid process that we try to simplify as much as possible to help patients quickly continue their regular activities of daily living.

Prevention has to do with a combination of things. One is patient selection. A discussion with an immunocompromised patient can help to identify and address potential modifications that could be done before surgery, such as weight loss and cessation of smoking. Patient education is also important, including practicing hygiene applications and reviewing instructions for postoperative care. Chronic illnesses must be addressed. Many patients that are on chronic anticoagulation can be at high risk of postoperative complications from bleeding, which places them at risk of infection. Trying to address chronic illnesses with the patient’s primary care doctor or through a program that will assist them to optimize their preoperative health, will certainly help to reduce the risk of infection.

Patients should take good care of themselves in general, from practicing good hygiene to eating correctly and not using smoking as a source of social behavior pattern. It is also important for patients to regain their activity level as soon as possible to exercise and live a healthy lifestyle.