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What is Prosthetic Joint Infection (PJI)?

Prosthetic joint infection (PJI), also known as periprosthetic joint infection, is described as an infection involving the joint prosthesis and surrounding tissue following surgery. PJI is still a relatively rare but devastating complication following a joint arthroplasty (replacement) such as total hip arthroplasty (THA) and total knee arthroplasty (TKA). A very small percentage of patients (less than 1%) who undergo joint arthroplasty may develop an infection around the joint following surgery.

Anatomy of the Joint

A joint is an articulation (junction) between 2 or more bones in the body. Muscles, tendons, ligaments, cartilage, and other soft tissue structures hold the joint in position. Joint replacement is a surgical procedure in which the damaged or worn-out articulating parts of the joint are removed and replaced with new artificial joint parts (prostheses) made of metal, plastic, or ceramic. The two most common joint replacement surgeries are knee replacement and hip replacement.

How Do Prosthetic Joint Infections Occur?

Your immune system is usually able to protect your body from bacteria or other infectious organisms by attacking it through the lymph system or bloodstream. However, your joint prosthesis does not have any blood vessels or lymphatic drainage, making it difficult for the immune system to gain access to and destroy these organisms. The bacteria can then multiply and cause the failure of the prosthesis.

Causes of Prosthetic Joint Infections

Prosthetic joint infections may occur immediately after the surgery or even many years later. The most common way bacteria or any other infectious organism reaches the prosthetic joint is through:

  • Breaks in the skin
  • Dental procedures such as tooth extraction
  • Other surgeries

Risk factors for Prosthetic Joint Infections

Factors that increase your risk of developing a prosthetic joint infection include:

  • Immunodeficiency disorders (e.g. HIV or lymphoma) 
  • Diabetes 
  • Peripheral vascular disease
  • Obesity
  • Immunosuppressive treatments 

Symptoms of Prosthetic Joint Infections

You may have developed a prosthetic joint infection if you notice the following signs and symptoms around your joint:

  • Pain and stiffness
  • Redness and warmth 
  • Fever and chills 
  • Weakness

Diagnosis of Prosthetic Joint Infections

Your doctor will discuss your symptoms, ask about your medical history, and perform a physical examination. Imaging studies such as X-rays and laboratory tests to identify the infection may also be ordered. Your doctor may also draw out fluid from your joint for a microscopic examination.

Treatment of Prosthetic Joint Infections

The various treatment options for prosthetic joint infections include:

Nonsurgical Treatment of Prosthetic Joint Infections

If only the skin and the underlying soft tissue are infected, oral or intravenous antibiotics may be enough to treat the condition. 

Surgical Treatment of Prosthetic Joint Infections

Surgical treatment is necessary if the infection has penetrated the deeper tissues around the joint. The various surgical treatment options include:

  • Debridement for Prosthetic Joint Infection: When a deep infection is diagnosed early, a surgical washout and debridement (removal of infected debris and dead tissue) may be all that is required to treat the condition. The joint prosthesis is thoroughly cleaned during this procedure and any plastic liners or spacers may be replaced.
  • Staged-Surgery for Prosthetic Joint Infection: If the prosthetic infection is diagnosed at a later stage, a 2-staged surgery may be performed.  The first stage involves the removal of the joint prosthesis, washout of the knee or hip joint, placement of an antibiotic spacer, which maintains the integrity of the joint, and the administration of intravenous antibiotics. The second stage, which occurs a few weeks later, is the placement of the new joint prosthesis after removing the antibiotic spacer and performing a surgical washout of the joint.
  • Single-Stage Surgery for Prosthetic Joint Infection: During this procedure, the infected joint implant is removed, the knee or hip joint is washed out, and the new joint implant is placed within the knee or hip. This relatively new method of treating a prosthetic joint infection is slowly gaining popularity. 

Prognosis Prosthetic Joint Infection

The prognosis for conservative treatment of prosthetic joint infection is good if the infection is identified early and treated promptly. In case the infection has been present for some time, revision surgery and replacement of the hip or knee prosthesis are usually necessary.