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Preventing Infection After Knee Replacement

Infection is one reason why total knee replacements fail or have to be replaced themselves. Surgeons do everything they can to keep this from happening. Looking for risk factors for infection is the focus of this study. The goal is to reduce reoperation rates because of septic failure. Septic failure refers to the breakdown of the area around the infection, in this case the bone and joint.

There are three main groups of risk factors in any surgical procedure: 1) patient-related, 2) surgery-related, and 3) provider- or care-related. Looking at small studies with only a few patients helps bring the problem of infection to our attention. But it's the large studies that help explain what went wrong. The more patients in the study, the lower the risk of false-negative results. False negative refers to the statistical analysis saying a factor was not significant or important when it really was.

In this study, over 43,000 patients were included. They could gather that many patients into one study because it was conducted at the Finland Hospital for Joint Replacement. In Finland, computer records are kept on every patient who has a total knee replacement. It's called the Finnish Arthroplasty Register. At the same time, hospitals complete and save records on every person ever discharged. This record is referred to as the Finnish Hospital Discharge Register.

The authors used these two databases combined together to gather data on all reoperations. Reoperation refers to total knee replacements that had to be redone or revised because of infection. By looking at the patients' characteristics of those who had to have the second operation, they were able to find common risk factors.

It turns out that having a previous knee surgery places patients at an increased risk for infection. Men are more susceptible to this than women. This was true after both the primary and second (revision) surgeries. The reason for this gender difference remains unknown. A prior history of rheumatoid arthritis (as opposed to osteoarthritis) also increased the risk of joint infection. And a previous fracture anywhere around the knee was an additional risk factor.

For primary (first-time) knee replacements, it seems that the type of implant used might make a difference. Patients receiving a constrained or hinged implant were more likely to develop a deep joint infection. The authors suspect the type of implant isn't really the issue that puts patients at increased risk of infection.

It's more likely the fact that patients with more advanced joint destruction receive these kinds of implants. It's the joint damage that puts the patient at increased risk of infection. Once the primary infection has been treated (with a new implant), recurring infection didn't seem to be related to whether it was a partial or complete revision procedure

Other findings from this study included the fact that patients with poor wound healing were more likely to need a repeat revision (third surgery). The infection rate was calculated based on subgroups of patients. The various subgroups included patients with other illnesses, patients with a cementless prosthesis (implant), patients who had no antiobiotic prevention, and patients who only got the antibiotic cement as a preventive precaution.

What's the take home message from this kind of study? Surgeons are advised to take preventive measures in any patient who needs a knee joint replacement. The patient should be given intravenous (IV) antiobiotic treatment. The surgeon should also use cement that has an antiobiotic in it to glue the implant in place. These two measures together may help prevent septic failure of the first joint replacement. If infection does occur, the same two preventive steps must be taken when performing a revision surgery.

With more and more older adults (some who are very fragile) getting knee replacements, every effort should be made to prevent joint infection. If infection does occur, a second surgery is often recommended. The surgeon may only need to débride (clear out the pus) the joint and the implant and administer antibiotics. When revision surgery is required, then every effort should be made to prevent reoccurrence of the infection that could then threaten the second implant.


Esa Jämsen, BM, et al. Risk Factors for Infection After Knee Arthroplasty. In The Journal of Bone & Joint Surgery. January 2009. Vol. 91A. No. 1. Pp. 38-47.


01/28/2009

*Disclaimer:* The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic.
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