Periprosthetic Joint Infection

What Are the Variables that Predispose Patients to Periprosthetic Joint Infection?

A number of important studies have been conducted that have evaluated the risk factors that predispose patients to periprosthetic joint infection. Although it is difficult to be inclusive of all of these factors, some of the most important factors relate to the immune status of the patients. Patients who are immunocompromised (eg, patients with diabetes, those on steroids and disease-modifying agents, and cancer patients) are at risk for developing infection in general and periprosthetic joint infection in particular. Patients with poor blood supply to the extremity (eg, vascular disease, smokers, and those with venous insufficiency and lymphedema) and those with skin problems (eg, psoriasis, eczema, or ulcers) are also at risk for periprosthetic joint infection.

One of the most important problems predisposing patients to periprosthetic joint infection relates to wound problems postoperatively. Patients with persistent wound drainage and hematoma formation are at particularly high risk for periprosthetic joint infection. Thus, patients with bleeding disorders (eg, platelet dysfunction, liver failure, and renal dysfunction), those placed on anticoagulation (particularly aggressive type), and those with poor healing potential (eg, malnourished, obese, or with previous irradiation) are also at risk of periprosthetic joint infection.

What Are the Diagnostic Challenges of Periprosthetic Joint Infection?

The major challenge is that there is no gold standard for diagnosis. If one were to rely on isolation of an organism from the joint as the gold standard, then accuracy for diagnosis of periprosthetic joint infection would be approximately 80% to 85%. In approximately 5% to 8% of patients with periprosthetic joint infection, an organism cannot be isolated (for various reasons), and in approximately 5% to 10% of patients, an organism may be isolated that does not represent true infection (false positive). Combining all the available diagnostic modalities to reach diagnosis of periprosthetic joint infection provides accuracy that is well below absolute. The other challenge for diagnosis of periprosthetic joint infection relates to a lack of “standard” definition for periprosthetic joint infection. What might be considered as infected by 1 surgeon or 1 institution may not be seen as such by another surgeon or institution. The promise of using molecular diagnostics in the future to meet these challenges is exciting.

What Are the Risk Factors of Periprosthetic Joint Infection Following Joint Arthroplasty?

On average, 1% to 2% of patients undergoing joint arthroplasty may develop periprosthetic joint infection. The risk for periprosthetic joint infection is higher after total knee arthroplasty compared to total hip arthroplasty (THA) (2%–2.5% vs 1.5%–2%) and also much higher after revision arthroplasty (5%–6%).

What Treatment Options Exist for Periprosthetic Joint Infection?

The majority of patients with periprosthetic joint infection require surgical intervention. The type of surgery depends on the time of presentation, and also the infecting organism to some extent. It is commonly believed that patients presenting with acute periprosthetic joint infection (within 4 weeks of index arthroplasty) may be candidates for irrigation and debridement of the infected joint and retention of the prosthesis. Recent studies by the Periprosthetic Joint Infection Consortium have demonstrated a high failure of irrigation and debridement, even for acute periprosthetic joint infection cases, especially those infected with methicillin-resistant organisms. Thus, indication for irrigation and debridement is changing. There is little to indicate for 1-stage exchange arthroplasty. I feel an indication for this procedure would be for patients presenting with acute periprosthetic joint infection after uncemented THA. The gold standard for periprosthetic joint infection remains the 2-stage exchange arthroplasty. For patients who have failed reconstructive surgery and continue to be infected, salvage operations in the form of resection arthroplasty or amputation may be required.

Why Is 2-Exchange Arthroplasty Considered the Gold Standard for Treatment of Periprosthetic Joint Infection?

When a prosthetic joint is infected, organisms form a biofilm on the prosthesis and become inaccessible to systemic antibiotics or immune cells. Thus, removal of biofilm and infecting organisms involves removal of the prosthesis, at least for chronic infections. Reimplantation of the joint with new prosthesis, although performed by some European surgeons, is believed to lead to a higher failure rate, as persistent organisms in the surrounding tissues around the joint or even the bone (osteomyelitis) are believed to lead to a higher failure. Thus, most surgeons in North America perform 2-stage exchange arthroplasty to enhance the success rate of surgical intervention. The placement of a temporary antibiotic-impregnated spaced in the interim between 2 stages also allows for effective delivery of antibiotics to the local tissues and eradication of organisms.

Is There a Connection Between Eradication of Periprosthetic Joint Infection and the Formation of Biofilm?

As mentioned above, infecting organisms usually gather on the surface of a prosthesis in a collection called biofilm. Biofilm has been studied extensively and is now believed to be a collection of sophisticated organisms. The organisms are covered with an umbrella of glycocalyx and extracellular proteins that protects them against the immune cells. The organisms are known to communicate through sophisticated molecular mechanisms that allow them to become planktonic (break from the group and float away) at appropriate times to enhance their chance of survival. Management of periprosthetic joint infection is challenging, as all organisms causing joint infection are able to form a biofilm.

What Future Steps Are Necessary to Reduce the Incidence of Periprosthetic Joint Infection?

We have discussed some factors that predispose patients to periprosthetic joint infection. One of the major issues that we have not mentioned relates to the environment in which joint arthroplasty is performed. Performing the surgery in an expeditious manner, administering the appropriate antibiotic prophylaxis in a timely manner, providing a clean operating environment (eg, use of laminar flow operating suits, and minimizing traffic in the operating room), gentle soft tissue handling, obtaining bleeding control, and proper wound closure are all extremely important to minimizing the risk for periprosthetic joint infection. The orthopedic community needs to evaluate the indications for joint arthroplasty and perhaps implement more strict indications for this effective surgical procedure. Perhaps patients with uncontrolled diabetes, malnourished or excessively obese patients, and patients with vascular insufficiency should not be subjected to total joint arthroplasty until their underlying condition is optimized. Periprosthetic joint infection is a real challenge and is likely to be the challenge of future decades. We all need to be actively engaged and implement strategies that can minimize this devastating complication.