Introduction: Who Should Undergo Diagnostics

If you have recently broken a bone, especially if the break was severe or required surgery, you should be alert to the possibility of infection developing. Not everyone who fractures a bone will develop an infection—in fact, most people heal without this complication. However, understanding when to seek diagnostic testing is important for catching infections early, when they are easier to treat.^[1]

You should seek medical attention and ask about diagnostic tests if you notice unusual changes around your fracture site. These changes might include increased pain that doesn’t improve with rest, warmth and redness that seem more intense than what you experienced initially, or swelling that appears to be worsening rather than getting better. If you see drainage coming from the wound, especially if it looks like pus, this is a clear signal to contact your doctor immediately.^[1]

People who have had open fractures—where the broken bone pierced through the skin or where a wound exposed the bone—are at higher risk and should be particularly watchful. The skin normally protects your body from bacteria in the environment, but when it is broken, harmful microorganisms can reach the bone directly. Similarly, if you had surgery to repair your fracture, there is a small window through which bacteria could have entered, even though surgeons take careful precautions.^[3]

Even if your fracture initially seemed straightforward, certain symptoms should prompt you to seek diagnostic evaluation. These include fever, chills, and night sweats that develop days or even weeks after your injury. You might also notice that a joint near the fracture, such as your knee or shoulder, becomes difficult to move. All of these signs suggest that something beyond normal healing is happening, and diagnostic tests can help determine whether an infection is present.^[1]

Classic Diagnostic Methods

When you visit your doctor with concerns about a possible infection after a fracture, they will start by examining the affected area carefully. During this clinical examination, the doctor looks for visible signs that might confirm or rule out infection. One of the most important confirmatory signs is a fistula or sinus tract—an abnormal opening that creates a direct pathway between the bone or surgical implant and the outside world. Another clear sign is visible pus or purulent drainage at the wound site. These findings alone can confirm that an infection is present.^[5]

Even if an infection seems obvious from the clinical examination, your orthopedic surgeon will likely order an X-ray. This imaging test helps the doctor see the bone structure and look for changes that might indicate infection, such as bone destruction or abnormal new bone formation. X-rays are a standard first step because they are widely available, relatively inexpensive, and provide useful information about what is happening beneath the skin.^[3]

Blood tests are another important diagnostic tool. When your body fights an infection, certain markers in your blood change. Doctors often check for elevated levels of inflammatory markers, which can suggest that your immune system is responding to bacteria. However, blood tests alone cannot tell your doctor exactly where the infection is located or what type of bacteria is causing it—they simply indicate that infection may be present somewhere in your body.^[3]

If the X-ray and blood tests do not provide a clear answer, your doctor may recommend additional imaging studies. A computed tomography scan, commonly called a CT scan, creates detailed cross-sectional images of your bones and soft tissues. This helps doctors see areas that might not show up clearly on regular X-rays. Another option is a magnetic resonance imaging scan, or MRI, which is particularly good at showing soft tissue infections and bone changes. A tagged white blood cell scan is a specialized nuclear medicine test where your white blood cells are labeled with a radioactive tracer and then reinjected into your body. Because white blood cells naturally migrate to sites of infection, this scan can help pinpoint exactly where an infection is located. These advanced tests are not always necessary, but they become valuable when the diagnosis remains uncertain.^[3]

The most definitive way to diagnose fracture infection involves obtaining tissue samples during surgery. When surgical exploration is performed, doctors can take deep tissue specimens or samples from the implant itself. If laboratory analysis identifies the same type of bacteria in at least two separate samples, this is considered strong confirmatory evidence of infection. Additionally, pathologists can examine tissue under a microscope to look for signs of infection. The presence of microorganisms in deep tissue or finding more than five polymorphonuclear leukocytes per high-power field in the tissue sample are both confirmatory signs of infection.^[5]

It’s important to understand that surface swabs—samples taken from the skin surface or superficial wound—are not reliable for diagnosing bone infection. The bacteria living on your skin may be completely different from those causing infection deep in the bone. Therefore, doctors need samples from deep within the affected area to accurately identify the cause of infection.^[5]

Diagnostics for Clinical Trial Qualification

When researchers design clinical trials to test new treatments for fracture-related infections, they need standardized ways to determine which patients actually have the condition being studied. This ensures that everyone enrolled in the trial truly has the disease and that results can be compared fairly across different studies and treatment centers.

Clinical trials typically use what are called confirmatory criteria to enroll patients. These are the same diagnostic signs that doctors use in regular practice: the presence of a fistula or sinus tract connecting to the bone or implant, visible pus, identification of matching bacteria from multiple deep tissue samples, presence of microorganisms in deep tissue confirmed by microscopic examination, or finding elevated numbers of inflammatory cells in tissue samples taken during surgery.^[5]

In addition to confirmatory criteria, clinical trials may also consider what are called suggestive criteria. These include general clinical signs such as redness, fever, increased pain, warmth, and swelling around the fracture site. While these symptoms alone cannot confirm infection, they indicate that further testing is needed. When combined with laboratory findings or imaging results, suggestive criteria help researchers identify patients who are likely to have infection and who might benefit from enrollment in a treatment study.^[14]

For clinical trials, precise classification of the infection is often required. Researchers may need to know exactly which bone is affected, how severe the infection is, whether the fracture has healed or remains unhealed, and whether any surgical hardware remains in place. This detailed characterization helps match patients to the most appropriate experimental treatment and allows researchers to understand which types of infections respond best to specific interventions.^[5]

The diagnostic process for trial qualification is typically more rigorous than for routine clinical care. Participants may undergo additional imaging studies, more frequent blood tests, or multiple tissue samplings to ensure accurate diagnosis and to monitor how well the experimental treatment is working. This comprehensive approach helps advance medical knowledge while also ensuring that trial participants receive thorough evaluation and care.^[5]