Infected Joint Replacement


Joint replacement surgery is an extremely effective way to manage end stage arthritis of joints such as the hip, knee or shoulder. Most patients are very satisfied with the result and are able to get back to the activities they love after they have rehabilitated from the surgery. Unfortunately about 1% of joint replacements become infected1 and for this group of people it is imperative they undergo further treatment to get rid of or at least control the infection.

Determining the exact cause of an infected joint replacement is very difficult. Things that contribute could be a patient’s overall health status at the time of the operation – individuals with diabetes, who smoke, who have autoimmune disorders or those who are obese are at a higher risk for infection.  Although hospitals and surgeons employ strict protocols to minimize the risk of infection during the surgery, there is risk that something could occur during the operation placing someone at a risk for infection.  

Finally, unidentified infections that a patient might have, such as dental issues, could lead to infection of the joint prosthesis. Infective organisms have an amazing ability to locate “foreign material” in a person’s body and migrate to this material. Therefore, if a person has an infection in another part of their body, the organisms may migrate to the total joint implants and grow around the implant and into the bone.

Symptoms of an Infected Joint Replacement

Signs and symptoms of a total joint infection may include:

  • Warmth and redness in the area of the joint
  • Increased pain or stiffness in a joint that was previously functioning quite well
  • Fever, chills, fatigue and/or nausea
  • Smelly, cloudy drainage from a surgical incision
     

Diagnosing an Infected Joint Replacement

It may take a combination of signs and symptoms and diagnostic tests to confirm that a joint is infected. The following diagnostic tests raise the suspicion for infection:

  X-rays may show evidence of loosening of the total joint implant caused by the bacteria destroying the bone around the implant.
  A bone scan may be positive when there is an active infection. There will be an area of increased radioactive dye uptake around the joint.
  Blood tests like erythrocyte sedimentation rate (Sed rate) or C-reactive protein (CRP) raise a suspicion for infection if they show an elevation in the markers that indicate an inflammatory process is occurring.
  An orthopedic surgeon may use a needle to withdraw fluid from the joint (aspiration), and have that fluid analyzed to see if the types of cells that fight infection (white blood cells called neutrophils) are elevated. An abnormally elevated white cell count can indicate there is an infection.

Treatment of Joint Infection

Superficial infections
If the infection is “superficial” meaning just the skin or soft tissue is infected, and the infection hasn’t moved deep into the joint, then a course of oral or intravenous (IV) antibiotics may be all that is needed to manage the infection.  When an infection is identified early, before it reaches the joint, the success of treatment is good. 

Deep infections
When an infection has reached the joint, surgery is necessary except in a situation where a person is too debilitated to tolerate a surgery.  
If an infection that has reached the joint is caught early, a surgical debridement (removal) of the affected soft tissue and washing out of the joint may be the extent of the surgical intervention. Any plastic components of the joint replacement will be replaced as well.  After the surgery a patient will complete a course of IV antibiotics, usually at least 6 weeks in duration. 

For an infection that occurs a longer time after the original joint replacement surgery, or is causing more severe symptoms, surgical intervention is a two-stage process. 

  The first stage involves removing the joint implants and any bone that is felt to be affected. It is important that the debridement (removal) of infected bone is very thorough and every attempt is made to remove any bone that is thought to be infected. Once this is complete, a temporary joint spacer is placed in the area. This spacer, which is usually made of an antibiotic infused material, holds the joint in anatomical alignment while helping to treat the infection.
  After this first surgery, a patient is started on a course of intravenous (IV) antibiotics that takes several weeks to complete. The antibiotics that are prescribed are specific for the type of organism that is causing the infection. Patients are followed closely by an infectious disease specialist while on IV antibiotics. Periodic blood tests are necessary to monitor any signs of infection or complications that might result from these very powerful medications.
  Once the antibiotic course has been completed, and the infectious disease specialist and orthopedic surgeon feel the infection has been managed, the second stage of the treatment is completed. This is a surgical procedure where the spacer is removed, the joint washed out, and a revision joint replacement prosthesis is placed in the joint.

When a patient is too ill or debilitated to undergo a surgical procedure and IV antibiotics, the managing physicians may recommend chronic antibiotic suppression therapy.  Chronic suppression requires the patient take oral antibiotics for the remainder of their lifetime. It is not a way to cure the infection however, but it may allow the patient to continue to avoid risky surgery while minimizing the symptoms of the infection for the remainder of their lifetime.

Joint infection is a potentially limb or life threatening complication that must be managed by the appropriate medical professionals. A team that includes an infectious disease specialist and orthopedic surgeon is imperative to effectively managing this difficult problem.


References
1. Kurtz SM, Lau E, Schmier J, Ong KL, Zhao K, Parvizi J. Infection burden for hip and knee arthroplasty in the United States. J Arthroplasty. 2008 Oct. 23(7):984-91