Causes and Diagnoses

Causes and Diagnoses of Prosthetic Joint Infections

Most prosthetic joint infections are the result of bacteria—often Staphylococcus aureus—present in the body or introduced during the surgery itself or subsequent procedures. In many cases, the microorganism is elsewhere in the body and waiting for an opportunity, such as a weakened immune system, to attack a vulnerable spot, such as a surgical wound or prosthesis.

Preventing prosthetic joint infections

You can help prevent PJIs by following these simple steps:

• Quit smoking.
• Ensure that your blood sugar is well controlled.
• Maintain good oral hygiene.
• Take antibiotics before dental procedures to prevent bacteria from entering the bloodstream through the gums.
• Take antibiotics before upper endoscopy or similar procedures to prevent bacteria from entering the bloodstream through a small lesion.

Diagnosing prosthetic joint infections

A diagnosis of prosthetic joint infection usually begins with a physical exam and review of your symptoms. If a PJI is suspected, your physician may also order:

• Blood tests: Blood samples will be taken to look for increased white blood cell count (indicating infection) and other indicators of inflammation in the body.
• Blood culture: A blood sample is stored in an environment that encourages bacterial growth to help identify what the infectious agent is.
• Needle aspiration: A sample of synovial fluid (lubricating liquid found in a joint) is removed from the joint for analysis under a microscope.
• Bone scan: This imaging test uses a small amount of radioactive material that will enhance an infected area on the computer screen.
• Computed tomography (CT) scan: A CT scan combines X-ray and computer technology to produce detailed cross-sectional images of tissue, and bone and blood vessels.
• Magnetic resonance imaging (MRI): This uses pulsed radio frequency and magnets to create images used for screening and diagnosis.
• Tissue biopsy: A small piece of tissue can be removed to study for presence of a microorganism. This is usually taken during surgery to replace the failing prosthetic.