One of the biggest reasons joint replacements fail is due to joint infection. Bacteria (sometimes referred to as “bugs”) and fungi can travel through the bloodstream. These pathogens can be carried by the blood to anywhere in the body including the joints. Once in the joint, they can form a biofilm on the surface of the implant.
Periprosthetic infection (in or around the joint) can develop anytime from early on (within the first six weeks of surgery) up to months or years later. Diagnosis can be a challenge. For example, this effect doesn’t show up on ordinary imaging studies such as X-rays. And it isn’t usually until the patient develops serious symptoms such as fever, nausea, and fatigue that there is even any awareness of the problem.
In some cases (like your mother), a channel from the joint out through the skin (called a sinus tract) is the first sign of a problem. The patient develops pain and oozing (infectious) drainage that sends him or her to the physician or clinic for help.
Early detection of joint infection requires constant diligence for patients who are at increased risk of joint infection. These can include older age, low socioeconomic status (poor nutrition and self-care), obesity, male gender, and knee implant. Poor general health due to comorbidities (other diseases) such as diabetes, cancer, or rheuatoid arthritis are additional risk factors.
Additionally, anyone who has had a previous joint replacement in the same joint is at increased risk of infection. Patients receiving a joint replacement who were in surgery for more than three hours or who received a blood transfusion from a donor (rather than using their own blood) face an increased risk of periprosthetic infection.
Even when there is suspicion of a periprosthetic infection, it isn’t always clear from the results of tests to diagnose periprosthetic joint infection that there is a problem. A suspected (but not confirmed) infection must be evaluated more carefully. Because of the biofilm that forms around the joint, the pathogens stick tight. They don’t always show up on blood tests. In the meantime, they become resistant to antibiotics.
So you can see the problem of recognizing and diagnosing joint infection for patients who received a joint replacement years ago is a sticky one. There are many factors and variables involved, not the least of which is the fact that these bacteria (“bugs”) hide in clever ways.
And as we pointed out, diagnostic testing and evaluation is not a simple process. However, there is hope that more sensitive and reliable diagnostic tests can be developed in the near future. Researchers are currently looking for telltale biomarkers in synovial fluid. Simple, inexpensive strips have been designed that can use one drop of synovial fluid to detect an enzyme present with bacterial infections. Other molecular techniques to detect fungi, viruses, bacteria, and other pathogens are also under investigation.
These tools won’t help your mother but hopefully, they will help prevent similar scenarios for other patients (including your mother should she ever have another joint replacement).