What Patients Need to Know About Total Joint Infections – Part One

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What Patients Need To Know About Total Joint Infections – Part One

I was recently asked questions about a potentially infected knee after undergoing a knee replacement by a family member. As I composed my thoughts, I realized this information would be helpful to others so here is some of that content.

It sounds like he does have an infection. Making that determination is not always straight forward. Anytime you put implants in a patient, infection is a risk. In large populations, the infection rate is about 2%. In smaller populations, it can be much higher. A partial list of increased risk for infection are: nutrition, diabetes, history of previous infection, obesity, cardiovascular fitness, smoking, anything altering the immune system like rheumatoid, cancer and cancer drugs, revision surgery or being multi time operated, length of operative procedure…
Sometimes infection is obvious and sometimes subtle. The most reliable method of determining the presence of infection is aspirating the joint and culturing the fluid. Still a lot of false results. Nuclear medicine studies like tagged white cell scans can help. There are some new blood tests, not commonly used but on the horizon.

The most common source of infection is the patient’s own bacteria. 80% of infected joints are infected by bacteria of the same type found in a patient’s nose. Eg they are carriers of bugs, as we all are, and there is a balance that keeps us healthy. Unbalance that and you get infected. Cutting the skin starts the process of risk by violating your protective barrier. That is why every surgery has some risk and implant surgeries are greater because the implant sort of alters the local immunity. Bacteria that otherwise would be treatable with antibiotics will not respond to antibiotics because they form a coating on the metal that makes antibiotics not work within a few days if infection. That is why you have to take the metal out and sterilize the area and start over.
Taking the implants out and replacing them in one step works better when you catch an infection early. Taking them out and putting in an antibiotic spacer and going on IV antibiotics and coming back later to put new implants in is more successful. No replant option is perfect and all carry a significant failure rate. In some patients, it is sometimes appropriate to just suppress the infection with antibiotics indefinitely.

Hopefully, this will give you some questions to ask. The most important one frequently not discussed, from my perspective, is what is the patient doing to help as well as the surgeon? The point is illustrated by this. I did a couple thousand consecutive surgeries when I was in the Army without an infection. I cannot go a week or two without a slow healing wound draining in Albany. What has changed? I am probably more skilled and operate faster which decreases infection risk. The answer is my patients have multiple risk factors not present in the relatively healthy military population. This is not meant to criticize the patients, but is factual and I try to explain infection risk especially to my arthroplasty patients so they at least understand what they could potentially do to mitigate risk. Generally working on aerobic fitness, smoking cessation, eating and resting and being clean etc. Honestly, I do not see people change much, but at least I have given them understanding and opportunity. I always control what is on my side of the relationship and that sometimes means, sadly, I do not offer to do an elective surgery on some people…to be continued.

Dr. T Scott McGee