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We’ve all experienced one infectious disease or another over our lifetimes. Colds, urinary tract infections, cellulitis, influenza, sexually transmitted infections, pneumonia…the list goes on and on. What’s much more uncommon is an infection affecting the bone, also called osteomyelitis. Let’s take a deep dive into the infection that affected the careers of Yao Ming, Mickey Mantle, and Al Kaline.
What is osteomyelitis?
The word osteomyelitis comes from a set of Greek roots. Osteomyelitis can be divided into three parts—osteo from osteon, meaning bone, myelo, meaning marrow, and itis meaning inflammation. All together, osteomyelitis means inflammation of the bone and its marrow, which comes from an infection of the bone. It’s rare, affecting only around 2 in 10,000 people (Parvizi, 2010). Its rarity is due to the resistance of healthy bone to infection—bone is only able to be infected under harsh circumstances where damage to the bone occurs, or a large amount of bacteria is introduced via injury, surgery, or severe infection of the tissue next to it.
Osteomyelitis is by no means a new phenomenon. The term was first used in the medical literature 1844 by a French surgeon, Auguste Nélaton. But don’t think that was the earliest case of osteomyelitis. There’s fossil evidence of osteomyelitis affecting Dimetrodon, a massive, 15-foot-long ancient animal with a sail on its back that lived in the Permian era (Moodie, 1921).
- Osteo means bone, myelo means marrow, and itis means inflammation.
- Osteomyelitis is rare, affecting only around 2 in 10,000 people.
- Most cases of osteomyelitis are due to a bacterial infection. Because of this, osteomyelitis is typically treated with antibiotics.
- There’s fossil evidence of osteomyelitis affecting Dimetrodon, a massive, 15-foot-long ancient animal with a sail on its back that lived in the Permian era.
What are the signs and symptoms of osteomyelitis?
A healthcare provider usually suspects osteomyelitis because of the symptoms you’re exhibiting. In children, osteomyelitis can cause weeks of fever, irritability, along with redness, swelling, and tenderness over the affected bone. In adults, common symptoms include tenderness, warmth, redness, swelling, bone pain, and pain in the infected area along with fevers and chills.
In children, the most common bones affected are the long bones in the arms and legs (Kradin, 2010). In adults, the bones in the spine, also called the vertebrae, are often affected along with the bones in the feet, especially in diabetics.
Osteomyelitis can be classified into acute osteomyelitis and chronic osteomyelitis. People with acute osteomyelitis have only experienced symptoms for a few days to a couple of weeks, while people with chronic osteomyelitis have had a long-standing infection for months or years.
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What causes osteomyelitis?
Typically, bone infections happen as a result of surgery or trauma to the bone itself, an infection of the area around the bone, or if there’s a systemic infection present and the pathogen is present in the blood. Most often, osteomyelitis is a result of a bacterial infection. Osteomyelitis is most commonly caused by a bacterium called Staphylococcus aureus (Castellazzi, 2016). In rare circumstances, there are cases where osteomyelitis is caused by fungal infections or autoimmune reactions.
How is osteomyelitis diagnosed?
If your healthcare provider suspects that you might have osteomyelitis, there is a battery of useful tests that they can do to evaluate you. First, they’ll take the history of your symptoms and then do a physical examination.
One physical test your healthcare provider might do is called “probing to bone.” If you have a worrisome wound that is suspicious for bone infection, they’ll take a stainless steel probe and try to touch the bottom of the wound. If they can go all the way to the bone, there is a high chance that osteomyelitis is present. This test is important, especially in evaluating for osteomyelitis in the context of diabetic ulcers.
Radiological scans are important in figuring out if you have a bone infection and where it might reside. There are several different scans available to healthcare providers. The fastest is the X-ray, which can sometimes identify areas of inflammatory reaction on the bone surface as well as areas of bone destruction. X-rays are also useful in identifying other possible causes of similar symptoms, including cancer and fractures. However, X-rays can struggle to pick up on small areas of infection or early signs of infection. Another commonly used scan is called an MRI (magnetic resonance imaging). MRI images can tell if a bone is infected much earlier than other scans, around 3 to 5 days after the infection begins. It’s typically one of the best tests for bone infections, picking up over 90% of cases with a low false-positive rate (Hatzenbuehler, 2011). However, it’s more expensive than other types of tests and can’t be used in people with metal in their bodies (although most metal hardware that is now used in surgery is safe for MRI).
The last types of imaging tests are called nuclear medicine tests. In these tests, you’re injected with a very small amount of a radioactive substance (don’t worry, this isn’t dangerous, and the amount of radiation you’re exposed to is minimal), which is then detected by the imaging machine. One test in this category is called technetium-99 bone scintigraphy, also called a bone scan. In this test, areas of bone metabolic activity will light up. This means areas of infection will light up, as well as any inflammation, or fracture. Another test in this category is called leukocyte scintigraphy, where white blood cells are tagged and injected into your body. Also called a white blood cell scan, the white cells used in the test will go to areas of infection, which can be helpful if your healthcare providers aren’t sure where an infection is coming from. Both of these tests are non-specific, meaning that it’s challenging for radiologists to tell if the problem areas shown on these scans are an infection or another inflammatory process.
Blood tests can also be extremely helpful. A healthcare provider can test you for inflammatory markers, like erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), that are often elevated in osteomyelitis. They might also evaluate the white blood cell level in your blood, which is usually high as well. Another test often done is called a blood culture, where a sample of your blood is tested for microorganisms in the lab.
The definitive diagnosis of osteomyelitis is made through what’s called a bone biopsy, where a small sample of the bone tissue is taken out and examined under the microscope. This is typically done through a surgical procedure. Healthcare providers can also use the sample of bone to detect what organisms are growing in it. This can help tailor antibiotic treatment to your specific case.
How is osteomyelitis treated?
Most cases of osteomyelitis are due to a bacterial infection. Because of this, osteomyelitis is typically treated with antibiotics. Most antibiotics have a difficult time penetrating the bone, which makes bone infections difficult to treat. This is why healthcare providers may ask that you go on intravenous antibiotic therapy for an extended length of time—weeks to months—so that the bacteria can be fully eradicated.
Another important part of treatment is removing pieces of dead or dying bone. These areas of bone are also called necrotic and, unfortunately, have no chance of healing or regenerating. This surgical procedure is called debridement. Debridement helps eliminate areas where bacteria can hide out and cause more problems down the line.
If osteomyelitis affects areas where hardware has been previously implanted, such as a spinal fusion or an artificial hip, that hardware will need to be removed and replaced. Additionally, if the infection came from an intravenous catheter, like the ones used in hemodialysis for people with kidney failure, the catheter will need to be removed. In serious cases, amputation of the affected limb can be the only way to treat osteomyelitis fully.
What are the risk factors for osteomyelitis, and how can we prevent it?
There are a few major risk factors for osteomyelitis. These medical conditions can raise the risk of osteomyelitis from something rare to something to worry about. The first of these is diabetes. In diabetes, damage to the blood vessels and nerves from high blood sugar can cause diabetic foot ulcers. The risk of developing a foot ulcer in diabetes is around 15% (Alexiadou, 2012). Diabetic foot ulcers are common precursors to osteomyelitis. Infection at the ulcer site can spread to the nearby bone, which can have a tough time battling the infection because of the poor blood flow to the affected area. The best way to prevent osteomyelitis in diabetes is to prevent diabetic foot ulcers. This involves controlling blood sugar levels as much as possible by staying on top of your diet and taking diabetes medications regularly. In the same vein, peripheral arterial disease is another risk factor for osteomyelitis, because poor blood supply can cause ulcers that then lead to osteomyelitis.
Problems with the immune system, such as those caused by human immunodeficiency virus (HIV) or chemotherapy, can decrease the body’s ability to fight off infection and predispose you to develop osteomyelitis. In particular, people with sickle cell anemia are at risk for osteomyelitis and joint infections. This is because the spleen, which has an important immune function, is damaged by sickle cell disease.
Trauma or surgery, especially one that results in open wounds, open fractures, or implanted hardware, can be another reason for bone infections. And finally, injection drug use is a major risk factor. Dirty needles can directly introduce bacteria into the bloodstream that then seed bones, causing infections.
If you’re worried about an infection anywhere in your body, the best step for you to take is to talk to your healthcare provider. They’ll be able to get you the necessary tests and treatment to get you back into tip-top shape.