Artificial Joint Infectious Arthritis

Often people with severe joint disease need to have the joint replaced (arthroplasty). Infections are more common in artificial joints (prosthetic joints) than are infections in natural joints. Frequently, artificial joint infections occur when bacteria enter

• The joint during surgery

• The wound shortly after surgery

• The bloodstream after surgery

Bacteria can enter the bloodstream via a skin infection, pneumonia, a dental procedure (rare), a procedure that requires insertion of an instrument into the body (called an invasive procedure), an infection of a catheter tube in the bloodstream, or a urinary tract infection.

About two-thirds of infections develop within 1 year of surgery. During the first few months after surgery, staphylococci are the bacteria most commonly responsible.

Artificial joint infectious arthritis can occur in people whose immune system is compromised either because of medications or disorders that weaken the immune system (such as rheumatoid arthritis, diabetes, cancer, or chronic kidney disease).

It can also occur in people who undergo surgical procedures. The type of surgery and whether complications develop from the joint surgery may also increase the risk of infections.

Symptoms of an infected artificial joint may include pain, swelling, and limited range of motion. Temperature may be normal.

Some people develop persistent joint pain while resting or bearing weight on the joint even after many months of successfully recovering from surgery.

• Analysis and culture of joint fluid

• X-rays and possibly a bone scan or white blood cell scan

Doctors base the diagnosis of an infected artificial joint on symptoms, an examination, and the results of a combination of tests.

Doctors examine the artificial joint to see whether a sinus tract has developed. A sinus tract is an abnormal channel from the joint to the skin that can develop when an infection exists.

Doctors remove a sample of joint fluid with a needle (joint aspiration) and have it examined in a laboratory for an increased number of white blood cells and tested for bacteria and other organisms. In the laboratory, the infecting bacteria is grown and identified (called a culture).

Doctors usually take x-rays to see whether the artificial joint has become loose or new bone has started to form. A bone scan (images of bone made after injecting radioactive technetium) or a white blood cell scan (images made after radioactive indium–labeled white blood cells are injected into a vein) may also be done.

If other tests have not excluded infection, doctors collect tissue around the artificial joint during a surgical procedure and send it to a laboratory for culture and analysis.

• Replacement of the artificial joint

• Long-term antibiotic therapy

Complete treatment of an infected artificial joint takes a long time.

Usually, all or part of an infected artificial joint is removed (revision arthroplasty) and the cement, collections of pus (abscesses), and infected tissues around it are also removed. A new artificial joint is then immediately implanted, or a spacer filled with antibiotics is inserted and a new artificial joint is implanted 2 to 4 months later with antibiotic cement. People who undergo either option need long-term antibiotic therapy. Whether replaced immediately or after the months-long delay, most of the new artificial joints do not become infected.

Sometimes the artificial joint or parts of it are removed because people have an uncontrolled infection or have lost too much bone. After this procedure, doctors may or may not fuse together the bones that form the joint.

Rarely, if infection cannot be controlled any other way, the part of the limb that contains the joint must be surgically removed (amputated).

• Sometimes taking antibiotics before certain procedures

People with artificial joints should discuss with their dentist or doctor whether they need preventive antibiotics before medical procedures (called prophylaxis). Most patients with artificial joints do not routinely need antibiotics before dental procedures. However, there are some procedures for which preventive antibiotics are sometimes given.

Sometimes doctors check for the presence of Staphylococcus aureus bacteria before surgery to replace a joint. A swab is used to take a sample from inside the nose, and the sample is examined for bacteria. If this bacterium is detected, an antibiotic ointment may be applied inside the nose to help prevent infections.