Medical Device Site Joint Infection

Medical device site joint infection, also known as periprosthetic joint infection, is a serious complication that can occur when bacteria contaminate an artificial joint implant. Although it affects only a small percentage of patients who undergo joint replacement surgery, this infection can lead to significant pain, multiple surgeries, and lasting impact on quality of life.

Table of contents

• What Is Medical Device Site Joint Infection
• Which Joints Can Be Affected
• How These Infections Develop
• Who Is at Higher Risk
• When Infections Occur
• Signs and Symptoms
• How Doctors Diagnose These Infections
• Treatment Options
• Preventing Infections

What Is Medical Device Site Joint Infection

Periprosthetic joint infection, prosthetic joint infection, PJI, artificial joint infection, infectious arthritis of prosthetic joint, septic arthritis of prosthetic joint

Medical device site joint infection, commonly called periprosthetic joint infection (PJI), happens when bacteria or other germs contaminate an artificial joint that has been surgically implanted in the body^[1]. This type of infection is markedly different from infections that affect natural bones or joints because it involves the complex interaction between microorganisms and artificial materials^[1].

Each year, hundreds of thousands of joint replacements are performed in the United States. Approximately 1 million hip and knee replacements alone take place annually, and this number is expected to increase significantly as the population ages^[1]. While most joint replacement surgeries are successful, about 1 to 2 percent of patients develop an infection after the operation^[1][2].

Which Joints Can Be Affected

• Hip
• Knee
• Shoulder
• Elbow
• Wrist
• Ankle

Prosthetic joint infections can involve any artificial joint in the body. The most commonly affected joints are the hip and knee, simply because these are the joints most frequently replaced^[6]. However, infections can also occur in shoulder, elbow, wrist, and ankle replacements^[6].

How These Infections Develop

Infections are caused by bacteria that contaminate the artificial joint. Although bacteria are naturally present in many parts of our body, such as our digestive tract and on our skin, they are usually kept under control by our immune system^[2]. However, artificial joints are made of metal, plastic, and ceramic materials, which makes it difficult for the immune system to fight bacteria that reach these implants^[2].

Bacteria can stick easily to metal surfaces. Since the metal implant does not receive blood flow, the immune system has a hard time identifying and attacking the bacteria^[2]. If bacteria gain access to the implants, they may multiply and cause a joint infection.

A key characteristic of these infections is the formation of biofilms. Only a minimal number of bacteria is needed to start an infection because the germs can attach to the surfaces of the artificial joint and form biofilms^[1]. A biofilm is like a protective wall made of a group of bacterial cells. This film shields the bacteria beneath it, making it very difficult for antibiotics to reach and kill them^[1]. Biofilms are notoriously resistant to a wide range of medications and are skilled at avoiding the body’s natural defenses^[1].

The bacteria that cause these infections typically come from the skin and may be introduced during the surgery itself^[1]. Alternatively, germs can reach the implant after surgery through the bloodstream from other infected areas of the body, or through direct contamination from nearby infected tissues^[1].

The most common ways bacteria enter the body include through breaks or cuts in the skin, during major dental procedures such as tooth extractions or root canals, and through wounds from other surgical procedures^[2].

Who Is at Higher Risk

Certain people have a higher chance of developing an infection after joint replacement surgery. Personal health factors that increase risk include^[2][3]:

• A prior infection in the same joint
• Earlier joint replacement or revision surgery in the same joint
• Tobacco use or smoking
• Rheumatoid arthritis
• Obesity
• Cancer or malignant tumors
• Diabetes mellitus
• Poor nutrition
• Psoriasis
• Advanced age
• A weakened immune system
• Immune deficiencies such as HIV or lymphoma
• Poor blood circulation to the hands and feet
• Treatment with medications that suppress the immune system

Surgical conditions during the operation can also increase risk. These include replacing two joints at the same time and operations that last longer than two and a half hours^[3].

After surgery, complications and other health issues raise the risk of infection. These include difficulties with wound healing, irregular heartbeat such as atrial fibrillation, heart attack, and any other infection in the body^[3].

A prolonged hospital stay or lengthy rehabilitation in a shared setting can also increase the risk of developing an infection^[6].

When Infections Occur

An artificial joint may become infected during the surgery itself, or anywhere from weeks to years after the operation^[2]. Doctors classify these infections based on when they occur^[3]:

Early onset infections happen less than three months after surgery. These infections are most commonly introduced during the operation itself and are usually caused by relatively aggressive germs^[3].

Delayed onset infections occur after three months but before 12 to 24 months following surgery. These infections are also typically acquired during surgery but are caused by less aggressive microorganisms, so the obvious signs of infection do not appear within the first three months^[3].

Late onset infections usually occur 12 to 24 months or more after surgery. These are likely due to bacteria that traveled through the bloodstream from another part of the body, though they may also be caused by extremely slow-growing germs that were introduced during surgery^[3].

Joint replacement infections can even occur years after surgery. Any infection elsewhere in the body can potentially spread to the artificial joint^[2].

Signs and Symptoms

It is important to know the warning signs of a prosthetic joint infection because many patients experience symptoms but assume they are simply part of normal recovery from surgery. The classical signs of infection, such as fever, elevated white blood cell count, and signs of widespread illness, are often absent^[1].

Common symptoms of medical device site joint infection include^[6]:

• Joint pain, which may start suddenly or develop gradually
• Increased pain or stiffness in a joint that was previously working well
• Swelling of the joint
• Warmth around the joint area
• Redness around the wound
• Drainage from the surgical site
• Fever
• Chills
• Night sweats
• Fatigue

Superficial infections that affect the surgical incision or wound usually take place anywhere from a few days to up to three months after surgery. These are usually not serious on their own, but some are linked to infection spreading to or from the artificial joint^[6].

Infection of the tissue surrounding the artificial joint may occur up to two years after surgery and can cause significant pain. The infection can also damage the new joint, potentially requiring a second surgery to remove and replace the device^[6].

How Doctors Diagnose These Infections

Diagnosing a prosthetic joint infection is not straightforward. There is no single test that confirms the diagnosis, and there is no universally accepted definition for this type of infection^[1]. The diagnosis requires supporting evidence from multiple sources, including clinical examination, laboratory tests, microbiological cultures, tissue examination under a microscope, and findings during surgery^[3].

The strongest indicator of infection is when fluid taken from the joint or tissue obtained during surgery grows microorganisms when cultured in a laboratory^[1].

Several organizations have developed guidelines to help doctors diagnose these infections, including the 2021 European Bone and Joint Infection Society criteria, the 2018 International Consensus Meeting criteria, and the 2013 Infectious Disease Society of America guidelines^[3]. These guidelines emphasize using a team approach that brings together specialists from different fields to make an accurate diagnosis^[3].

Treatment Options

Treatment for medical device site joint infection can be complex and often requires costly and prolonged hospital stays, weeks or months of antibiotic therapy, and frequently multiple surgical procedures^[1]. Despite antibiotics and preventive measures, patients with infected joint replacements often require surgery to cure the infection^[2].

Several treatment approaches are available, and the choice depends on many factors including the stability of the implant, timing of the infection, the patient’s overall health and age, immune system status, aggressiveness of the infecting germ, and the patient’s wishes^[14].

Treatment options include^[14]:

• Suppressive antibiotics: Long-term antibiotic treatment to control but not cure the infection
• Arthroscopic irrigation and debridement: Cleaning the joint using minimally invasive techniques
• Open debridement with insert exchange: Opening the joint surgically to clean it and replacing some components
• Single-stage reimplantation: Removing the infected implant and immediately placing a new one during the same surgery
• Two-stage reimplantation: The most common approach, which involves removing the infected implant first, treating the infection, and then placing a new implant in a second surgery

In the two-stage approach, which is frequently used, the infected joint is first removed and the area is thoroughly cleaned. A temporary implant is then placed. Following this initial procedure, patients typically receive intravenous antibiotics for at least six weeks^[20]. When it is safe to do so, the temporary implant is removed and permanent replacement implants are installed^[20].

The ultimate goal of treatment is to eliminate the infection and restore a pain-free, well-functioning joint. However, long-term results and recovery times can vary greatly from patient to patient.

Preventing Infections

Prevention is crucial in combating surgical site infections and prosthetic joint infections. Several strategies can help reduce the risk^[17]:

Before surgery, doctors work to optimize patients’ health conditions. Modifiable risk factors such as uncontrolled diabetes, high blood pressure, malnutrition, high body weight, and other medical conditions should be addressed and brought under control before elective joint replacement surgery^[17].

During surgery, several precautions are taken. These include giving patients antibiotics both before and after the procedure, keeping surgical time as short as possible to minimize exposure, using strict sterilization techniques for all operating instruments, and maintaining a sterile surgical environment^[16].

After surgery, patients should take antibiotics before any major dental work, such as tooth extractions or root canals, as these procedures can introduce bacteria into the bloodstream that may reach the artificial joint^[16].

While these prevention strategies can greatly reduce the risk of infection, they cannot completely eliminate it because there are factors beyond medical control^[16]. However, following recommended preventive measures gives patients the best chance of avoiding this serious complication.