Total knee replacements (TKAs) that become infected can be very difficult to treat effectively. Despite a high cost for the treatment, the outcome may not always be ideal, leaving patients with pain and decreased mobility.
As with most complications, prevention is the best medicine. This involves identifying patients who may be at higher risk of developing infections following TKAs. That being said, the appropriate treatments must be identified once infection has set in.
the signs and symptoms of infection in a TKA are usually the obvious ones of pain, difficulty in movement, mild inflammation and recurrent effusions (fluid in the knee). Blood tests can also indicate the presence of infection. Joint aspiration, withdrawal of fluid from the joint, is another method of diagnosis but could require several samples before an infection is found. Other methods, such as scans may not detect infection within the first year after surgery, because of how the joint is healing.
Treatment of these infections can be done through conservative methods such as antibiotics, right through to more aggressive methods, such as replacing the joint or even amputation. The choice of treatment greatly depends on the patient, the patient’s lifestyle, and – of course – the infection itself.
Eliminating the infection completely is the ultimate goal. If debriding, or cutting away of infected and dead tissue, is performed, it must be done meticulously and completely if the goal is to keep the current joint. It would be necessary to remove the liner in the knee to be sure to access any surfaces hidden or inaccessible below the liner. The authors of this article write that such a procedure is more likely to be successful if the infection is caused by the Staphylococcus epidermis bacteria and not as successful if it is caused by the Staphylococcus aureus bacteria. As well, for this procedure to work, it is important that the infection has not been present for more than three weeks and the patient is not immunocompromised.
If debriding and antibiotic treatments are not an option, amputation or replacement may be necessary. The type of surgery will greatly depend on the remaining healthy bone and ability to tolerate another replacement. There is a two-step procedure that is an option for some patients. This includes removing the infected implant and replacing it with a temporary spacer, while administering antibiotics to the area. If the surgery is done without using a spacer, the patient can run into problems with the joint a few weeks later when a new implant is attempted. Spacers allow the knee to stay in the proper position and prevent contractions and the build up of scar tissue.
The two-step or two-tier option has become increasingly popular in situations where the infection is not treatable in the less invasive methods. The authors conclude, “For deep infection of more than three weeks’ duration, most expert surgeons recommend a staged approach to management.”