Artificial joints can become infected by bacteria.
Infections are more common among artificial joints. Frequently, these infections occur when bacteria enter the joint during surgery, the wound shortly after surgery, or the bloodstream after surgery. Bacteria can enter the bloodstream via a skin infection, pneumonia, a dental procedure, 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.
Symptoms may include pain, swelling, and limited range of motion, and temperature may be normal. Some people fall, in part because their joint was painful or unstable. About 20% of people have had surgery to correct something in their artificial joint before symptoms started. Some people develop persistent joint pain while resting or bearing weight on the joint even after many months of successfully recovering from surgery.
Doctors base the diagnosis 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 (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 ruled out infection, doctors collect tissue around the artificial joint during a surgical procedure and send it to a laboratory for culture and analysis.
People with artificial joints should discuss with their dentist or doctor whether they need preventive antibiotics before medical procedures. Procedures for which preventive antibiotics are sometimes given include those involving the teeth, the digestive organs, and the urinary tract.
Complete treatment of an infected artificial joint takes a long time. Usually, all or part of an infected artificial joint is removed and the cement, collections of pus (abscesses), and infected tissues around it are also removed. A new artificial joint is then immediately reattached 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, many (although fewer than half) of the new artificial joints also become infected.
If people cannot tolerate surgery, doctors may try only long-term antibiotic therapy. Sometimes the 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 amputated.
Last full review/revision May 2013 by Steven Schmitt, MD