The 13 co-authors of this article sat on a committee together to come up with Clinical Practice Guidelines (CPGs) for the diagnosis of infections in joint replacements. The proposed guidelines were approved by the American Academy of Orthopaedic Surgeons (AAOS) in June of 2010 and published here for all to see.
Clinical Practice Guidelines (CPGs) are an important tool in helping physicians keep up-to-date with what the evidence says about treatment of various problems and conditions. The goal is to improve treatment based on high-quality evidence.
CPGs are especially helpful when care for musculoskeletal problems is provided by a wide variety of health care professionals. This could include emergency medical staff, primary care physicians, Physical Therapists, physician assistants, chiropractors, orthopedic surgeons, athletic trainers, and others.
The 15 recommendations contained in these Clinical Practice Guidelines for the diagnosis of infections of joint replacement implants are based on a systematic review of all available research results in this area.
Ten of the 15 are based on high-quality evidence. A full viewing of all 15 is available on-line at http://www.aaos.org/research/guidelines/PJIguideline.asp. Here's a quick review of the most reliable points.
Anyone suspected of a periprosthetic joint infection (PJI) should be screened using two tests: erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP).
Patients with higher lab values indicating inflammation (e.g., ESR and CRP tests) are more likely to have an infection. Further testing is required. This is based on a probability and statistics model.
One other lab test (i.e., gram stain) should not be used to say there is no joint infection. In other words, the gram stain test is not a good rule-out test.
Whenever ESR and CRP tests are abnormal, fluid should be aspirated (drawn) from the joint and sent for testing to confirm infection and type of pathogen (bacteria).
Aspiration is not necessary when there are normal ESR and CRP levels. Hip aspiration can be painful and difficult to do without actually injecting the joint with more bacteria. Therefore hip aspiration is not done routinely (unless there are abnormal screening tests) and especially not when surgery isn't going to be done.
Positive ESR and CRP tests in patients who are NOT having surgery should be retested in three months.
Repeat joint aspiration tests for the knee follow similar guidelines as for the hip but the need for repeated testing is much less for the knee. Joint infections of knee implants are easier to diagnose and confirm compared with hip infections.
Taking fluid from the joint to test it for the specific bacteria present should be done before any antibiotics are given. Sometimes this doesn't happen and the patient is put on antibiotics immediately regardless of what kind of pathogen is present.
If antibiotics have been prescribed, then joint culture by aspiration must wait until two weeks after the patient stops taking the drugs. Discontinuing the medication is important because taking antibiotics limits the number of bacteria present and prevents accurate testing.
The need for diagnostic imaging (PET scans, bone imaging, CT scans, MRIs) is unclear. Patients who are not going to have surgery probably don't need the added testing.
When surgery is done, fluid should be taken from the joint and retested. In fact, more than one sample should be drawn and tested. More than one positive test increases the certainty that there is a joint infection.
The bad effects of implant infection suggest the need for antibiotics before the first joint replacement surgery is done. Prophylactic (preventive) antibiotics preoperatively to prevent infection.are advised even for low risk patients.
For those who are interested in these clinical practice guidelines, the authors advise remembering two additional factors that can affect decisions. First, each patient is unique and must be evaluated based on his or her situation. These guidelines are exactly that: guidelines, not a standard of practice that should be applied in a cookie-cutter fashion.
Second, health care professionals should not assume the clinical practice guidelines outlined here are set in stone or indefinite. As new studies are published, these guidelines may become outdated.
The guidelines help level the playing field, so-to-speak (everyone uses the same guidelines to direct treatment decisions). Even so, it will be necessary to update the guidelines every five years and possibly even remove them if they are outdated.
Reference: Craig Della Valle, MD, et al. Diagnosis of Periprosthetic Joint Infections of the Hip and Knee. In Journal of the American Academy of Orthopaedic Surgeons. December 2010. Vol. 18. No. 12. Pp. 760-770.