Medical device site joint infection, also known as periprosthetic joint infection, is a serious complication that can occur after joint replacement surgery. Though these infections affect only a small percentage of patients who receive artificial joints, they can have profound physical, emotional, and financial consequences, requiring extended treatment and sometimes additional surgeries.
Epidemiology
Approximately one million hip and knee joint replacement surgeries are performed annually in the United States, with this number expected to increase significantly as the population ages. In 2010 alone, 719,000 total knee replacements and 332,000 total hip replacements were performed in the country. By 2030, estimates suggest that 3.48 million primary total knee and 572,000 primary total hip replacements will be performed annually in the United States.[1][3]
Despite advances in surgical techniques and prevention strategies, medical device site joint infections remain a concern. The incidence of these infections ranges from approximately one to two percent of all hip and knee replacement procedures. Some sources report rates as low as 0.5 percent for certain joint replacements, while others cite up to three percent depending on the type of joint involved.[1][2][10]
While the overall infection rate may seem modest, the actual number of affected patients continues to grow as more joint replacement surgeries are performed worldwide. These infections have become the primary reason for revision surgery in many cases, accounting for approximately 14.8 percent of total hip replacement revisions and 25.2 percent of total knee replacement revisions.[4]
The prevalence of infections caused by resistant bacteria has also been rising over the past 15 years, largely due to overuse of antibiotics in community and healthcare settings, inappropriate antibiotic strategies, and increased hospital stays in intensive care units.[14]
Causes
Medical device site joint infections are caused by microorganisms, predominantly bacteria, though fungi can occasionally be responsible. The infection develops when these microorganisms contaminate the artificial joint and establish themselves on or around the implanted device.[1][2]
The artificial joint itself is a foreign body, and because it is made from materials like metal, plastic, or ceramic, the body’s immune system has difficulty fighting infections that reach these implants. Bacteria tend to adhere to metal surfaces, and since the implant does not receive blood flow, the immune system struggles to identify and attack bacteria that settle there.[2][8]
Only a minimal amount of bacteria is needed to initiate an infection around a prosthetic joint—much less than what would be required to infect a natural joint. Once bacteria attach to the implant surface, they can form structures called biofilms. These biofilms act like protective walls made of groups of bacterial cells that shield the bacteria underneath, making them highly resistant to antibiotics and difficult for the body’s immune defenses to eliminate.[1][16]
The bacteria that cause these infections typically come from the skin’s normal bacterial population. They may be introduced during the surgical procedure itself, when the joint is being implanted. Alternatively, bacteria can reach the artificial joint after surgery through the bloodstream, traveling from infections elsewhere in the body, or through direct contact from infected tissues near the joint.[1][2]
There are three main pathways through which bacteria enter the body and cause infection. The first is through breaks or cuts in the skin. The second is during major dental procedures such as tooth extractions or root canals, when bacteria from the mouth can enter the bloodstream. The third is through wounds from other surgical procedures performed after the joint replacement.[2][8]
Risk Factors
Certain individuals face a higher likelihood of developing a medical device site joint infection due to various factors related to their health, lifestyle, medical history, and the surgical process itself.[2][3]
Patient-related factors that increase infection risk include having had a previous joint replacement or infection at the same site. Tobacco use is another significant risk factor, as smoking impairs wound healing and weakens the immune system. Obesity increases risk as well, partly because excess weight can complicate surgery and slow healing. People with rheumatoid arthritis, a condition where the immune system attacks the joints, are more susceptible to infection.[2][3]
Medical conditions that weaken the immune system significantly raise infection risk. These include diseases like HIV, lymphoma, or other cancers. Patients with diabetes face higher risk because elevated blood sugar levels can impair healing and immune function. Poor circulation to the hands and feet, known as peripheral vascular disease, also increases vulnerability to infection. Individuals taking medications that suppress the immune system, such as corticosteroids or drugs used after organ transplants, are at greater risk.[2][3][6]
Having an active infection elsewhere in the body at the time of surgery dramatically increases the chance of the artificial joint becoming infected. Poor nutrition and conditions involving benign or cancerous tumors also raise risk. Advanced age can be a factor, as older individuals may have weaker immune systems.[6][10]
Factors related to the surgery itself can also contribute to infection. If two joints are replaced at the same time, or if the operation lasts more than two and a half hours, risk increases. After surgery, complications such as difficulties with wound healing, irregular heartbeat like atrial fibrillation, heart attack, or any other infection can raise the likelihood of developing a joint infection.[10]
A prolonged hospital stay following surgery or lengthy rehabilitation in a communal setting can also increase exposure to infectious organisms.[6]
Symptoms
The symptoms of a medical device site joint infection can vary, and the classic signs of infection such as fever, elevated white blood cell count, and signs of widespread infection in the blood are often absent. This makes recognizing the condition more challenging.[1]
The most commonly reported symptom is pain in the joint that has been replaced. This pain may appear suddenly or develop gradually over time. It is especially concerning if a joint that had been functioning well and was pain-free begins to hurt again.[6][10]
Other symptoms include increased stiffness in the joint, making movement more difficult than it had been previously. Swelling around the joint area is common, as is warmth and redness of the skin over the joint. Some patients notice drainage coming from the surgical wound, which can be a clear sign of infection.[6][10]
Patients may also experience general symptoms that affect the whole body. These include feeling unusually tired or fatigued, running a fever, experiencing chills, and having night sweats. These systemic symptoms indicate that the body is fighting an infection.[6][10][16]
Infections can develop during the hospital stay immediately after surgery, after the patient has returned home, or even years after the joint replacement procedure. This wide timeframe means that patients should remain alert to these symptoms long after their surgery has healed.[2]
Prevention
Preventing medical device site joint infections involves multiple strategies implemented before, during, and after surgery. While it is impossible to eliminate risk entirely, numerous measures can significantly reduce the likelihood of infection.[17]
Before surgery, patients should work with their healthcare team to optimize their overall health. Managing conditions like diabetes is particularly important, as uncontrolled blood sugar levels can impair healing and increase infection risk. Healthcare providers often recommend achieving better control of blood glucose before proceeding with elective joint replacement. Other conditions requiring optimization include high blood pressure, malnutrition, chronic liver or kidney disease, and reducing excess weight if possible.[17]
Patients are typically advised to stop smoking well before surgery, as tobacco use significantly increases infection risk by impairing wound healing and weakening the immune system. Any active infections in the body, whether urinary tract infections, skin infections, or dental problems, should be treated before joint replacement surgery.[3]
During the surgical procedure, healthcare teams use strict sterilization techniques and protocols for all instruments and maintain a sterile operating environment. Many facilities use special air filtration systems called laminar flow to reduce airborne bacteria in the operating room. Surgeons aim to complete procedures efficiently to minimize the time the surgical site is open and exposed.[17]
Antibiotics play a crucial role in prevention. Patients receive antibiotics before surgery begins and often for a short period afterward. These prophylactic antibiotics help prevent bacteria from establishing an infection during the vulnerable perioperative period.[2][17]
After surgery, protecting the artificial joint from potential sources of infection is important. Patients are advised to take antibiotics before undergoing major dental procedures such as tooth extractions or root canals. This helps prevent bacteria from the mouth from traveling through the bloodstream to the artificial joint. Any cuts or wounds on the skin should be cleaned and cared for promptly to prevent bacteria from entering the body.[2][8]
Patients should be vigilant about signs of infection anywhere in their body and seek prompt treatment, as infections elsewhere can spread to the artificial joint through the bloodstream. Maintaining good overall health, including proper nutrition and managing chronic conditions, helps support the immune system in protecting against infection.[2]
Pathophysiology
The development of a medical device site joint infection involves complex interactions between bacteria and the body’s immune system, with the artificial joint playing a central role in making infection more likely and harder to treat.[1]
Artificial joints create a unique environment in the body. Unlike natural tissues, these implants are made from materials such as metal alloys, strong plastics called polyethylene, or ceramic. These materials do not receive blood flow, which creates a major challenge for the immune system. Normally, when bacteria enter the body, white blood cells travel through the bloodstream to the site of infection and attack the invading organisms. However, because artificial joints have no blood supply, immune cells cannot easily reach bacteria that have attached to the implant surface.[2]
Bacteria have a natural tendency to stick to artificial surfaces, particularly metal. Once bacteria attach to the implant, they begin forming biofilms. These are complex structures where bacterial cells group together and create a protective coating around themselves. Think of a biofilm as a fortress that bacteria build to shield themselves from threats. This coating acts as a barrier that prevents antibiotics from penetrating and reaching the bacteria underneath. The biofilm also helps bacteria evade the immune system’s detection and attack mechanisms.[1][16]
The amount of bacteria needed to cause an infection around an artificial joint is remarkably small—far less than would be required to infect a natural joint or bone. This is because the presence of the foreign material significantly reduces the body’s ability to fight off even small numbers of bacteria.[1]
The bacteria involved in these infections typically originate from the skin’s normal bacterial population. Common culprits include Staphylococcus aureus, a relatively aggressive bacterium, and coagulase-negative staphylococci, which are less aggressive but still capable of causing infection. Gram-negative bacteria and anaerobic organisms, which thrive in environments without oxygen, can also cause these infections. The specific type of bacteria often relates to when the infection develops after surgery.[3]
Early infections, occurring within three months of surgery, are usually caused by more virulent or aggressive bacteria that were introduced during the operation. These bacteria multiply quickly and cause obvious symptoms relatively soon. Delayed infections, appearing between three months and one to two years after surgery, are typically caused by less aggressive organisms. These bacteria grow more slowly, which is why symptoms take longer to appear even though the bacteria were likely introduced during surgery. Late infections, developing more than one to two years after surgery, often result from bacteria that spread through the bloodstream from infections elsewhere in the body, though they can also be caused by extremely slow-growing bacteria from the time of surgery.[3]
Once infection is established, the body mounts an immune response, but this response is often insufficient to clear the infection due to the biofilm and the lack of blood supply to the implant. Inflammation develops around the joint, causing pain, swelling, warmth, and redness. The infection can damage surrounding tissues and may loosen the artificial joint, compromising its function and causing significant discomfort.[13]
