Acute Osteomyelitis

Acute osteomyelitis is a serious bone infection that develops rapidly when bacteria or fungi spread to your bones, usually through your bloodstream. If not treated quickly, it can cause permanent bone damage and serious complications.

Table of contents

• What is acute osteomyelitis?
• What causes this infection?
• Who is at higher risk?
• What are the symptoms?
• How is it diagnosed?
• How is it treated?
• Possible complications

What is acute osteomyelitis?

Acute osteomyelitis is a new bone infection that develops after germs spread to your bones^[1]. It is the most common type of osteomyelitis (bone infection)^[1]. The term “acute” means the infection happens quickly, usually within two weeks after disease onset^[4].

This condition causes painful swelling in your bone marrow (the spongy center of some bones)^[1]. While it can affect any bone in your body, the location depends on age. Children most commonly develop acute osteomyelitis in their leg or arm bones, particularly in the metaphysis (growing regions) of long bones^[1][4]. Adults usually develop it in their vertebrae (the bones that make up your spine) or hips^[1].

Before antibiotics became available in the 1940s, mortality rates from osteomyelitis were very high^[3]. Today, with early treatment, the outlook is much better. However, if not treated in time, acute osteomyelitis can cause permanent bone loss and necrosis (tissue death)^[1].

What causes this infection?

Infections that spread to your bones cause acute osteomyelitis^[1]. Healthy intact bone normally resists infection, but bone becomes vulnerable when large amounts of bacteria are introduced through trauma, loss of blood supply, or the presence of foreign bodies^[3].

The infection usually happens when germs on the surface of your skin, such as at a wound or surgery site, get into your bloodstream and spread to your bone marrow^[1]. This is called hematogenous osteomyelitis, meaning the bacteria are carried through the blood^[4]. This type occurs predominantly in children and is often seeded through the bloodstream^[4].

Staphylococcus aureus is the most common bacteria causing acute osteomyelitis^[4][6]. This type of bacteria is commonly found on the skin^[6]. Other bacteria that can cause infection include Group A streptococcus, Streptococcus pneumoniae, and Kingella kingae in children^[13]. In newborns, Group B streptococcal infection is most common^[13].

Certain bacteria have special abilities to attach to bone and survive. For example, Staphylococcus aureus can attach to bone by expressing receptors for components of the bone matrix such as collagen and fibronectin^[3]. Some bacteria can also survive inside bone cells and create protective coatings called biofilms around themselves, which helps explain why bone infections can persist and why treatment must be prolonged^[3].

Who is at higher risk?

Anyone can develop an infection that causes acute osteomyelitis, but certain people have a higher risk^[1]. Children are most often affected by acute hematogenous osteomyelitis, with more than half of cases occurring in patients younger than five years^[13].

People at increased risk include those who^[1]:

• Are younger than 20 or older than 50
• Have open wounds after an injury or trauma
• Have recently had surgery, especially joint replacement or other procedures where pieces are implanted into the body, including pins and screws to repair broken bones
• Experience puncture injuries (something stabbing into the body)
• Have pressure injuries (bedsores)

People with certain health conditions or who need treatments that weaken their immune system are more likely to develop acute osteomyelitis^[1][6]:

• Sickle cell anemia
• Diabetes (especially if you have diabetes-related foot ulcers)
• People who take immunosuppressants
• People who need hemodialysis
• HIV infection
• Rheumatoid arthritis
• Kidney disease that needs dialysis

Children may also be more likely to get osteomyelitis after having a respiratory infection or chickenpox^[18].

What are the symptoms?

Children with acute osteomyelitis typically present within several days to one week after the onset of symptoms^[4]. The symptoms can vary depending on which bones are infected, but the most common signs include^[1][2][6]:

• Fever
• A general feeling of being sick or unwell
• Bone pain
• Chills
• Sweating
• Nausea and vomiting
• Skin discoloration
• Swelling (inflammation)
• A feeling of heat or warmth on your skin
• Pus or discharge (if the infection is near a wound or surgery site)

In children, additional signs include fever, irritability, and lethargy^[4]. Typical clinical findings include tenderness over the involved bone and decreased range of motion in adjacent joints^[4]. Young children may not always get a high temperature with osteomyelitis, and they may not want to use an arm or leg and seem irritable^[18].

You should see a healthcare provider if you have a fever and bone pain that gets worse^[2]. People at risk of infection because of a medical condition, recent surgery, or injury should see a healthcare provider right away if they have symptoms of an infection^[2].

How is it diagnosed?

Your healthcare provider may feel the area around the affected bone for tenderness, swelling, or warmth^[7]. Several tests are used to diagnose acute osteomyelitis and identify which germ is causing the infection.

Blood tests can show high levels of white blood cells and other markers in the blood that may mean your body is fighting an infection^[7]. Blood tests also may show which germs caused the infection^[7]. A type of blood test known as a blood culture may be used to identify the type of bacteria causing the infection^[6]. However, no blood test alone can tell whether you have osteomyelitis^[7].

Imaging tests are essential for evaluation. Plain film X-rays should be performed as initial imaging, but sensitivity is low in the early stages of disease^[9]. X-rays can show damage to a bone, but the damage may not show on X-rays until osteomyelitis has been there for weeks^[7]. You may need more-detailed imaging tests if your infection is more recent^[7].

Magnetic Resonance Imaging (MRI) with and without contrast media is the imaging modality of choice for suspected osteomyelitis^[9]. Using radio waves and a strong magnetic field, MRI scans can make detailed images of bones and the soft tissues around them^[7]. Other imaging tests may include CT scans or bone scans^[7].

A bone biopsy can show what type of germ has infected your bone^[7]. Sometimes your doctor will take a tissue or bone biopsy, where a small piece of bone is removed for testing^[6]. The preferred diagnostic criterion for osteomyelitis is a positive bacterial culture from bone biopsy^[9]. Knowing the type of germ helps your healthcare professional choose an antibiotic that works well for the type of infection^[7].

How is it treated?

Acute osteomyelitis is treated with antibiotics^[6]. Antibiotics are the primary treatment option and should be tailored based on culture results and individual patient factors^[9]. You may need treatment in hospital, or you might be able to take antibiotics at home^[18].

At first, you will need antibiotics intravenously (IV – through a vein), and later as oral tablets as your symptoms improve^[6]. You’ll usually take antibiotics for 4 to 6 weeks^[18]. For optimal results, antibiotic therapy must be started early, with antimicrobial agents administered parenterally for at least four to six weeks^[4]. Children with osteomyelitis can typically be treated with a four-week course of antibiotics^[13].

Research has shown that in adult patients hospitalized with chronic osteomyelitis, parenteral followed by oral antibiotic therapy appears to be as effective as long-term parenteral therapy^[9]. It’s important to finish a course of antibiotics even if you start to feel better^[18]. Taking the full dose of any medication your healthcare provider prescribes to kill the initial infection is the best way to prevent chronic osteomyelitis^[1].

You can take painkillers to ease the pain^[18]. If the infection is in a long bone (such as an arm or leg), you may be fitted with a splint so you do not move it as often^[18].

Surgery may be needed in certain cases. Acute osteomyelitis must be treated surgically to drain pus and prevent bone necrosis^[11]. You’ll usually need an operation if^[18]:

• A build-up of pus (abscess) develops in the bone and the pus needs to be drained
• The infection presses against something else, for example, the spinal cord
• The infection has lasted a long time and damaged the bone

If the infection is treated quickly (within 3 to 5 days of it starting), it often clears up completely^[18].

Possible complications

If not treated quickly, acute osteomyelitis can cause serious long-term problems^[18]. The infection can cause permanent bone loss and necrosis (tissue death)^[1]. If untreated, osteomyelitis can lead to blood poisoning (sepsis) and an abscess in the bone^[6].

Bone infections that aren’t completely cured after treatment can linger in your body and come back (recur) months or years later, developing into chronic osteomyelitis^[1]. The incidence of relapse following an apparently ‘successful’ treatment remains high^[20].

Early treatment with antibiotics and surgery can help reduce the chance of permanent bone damage^[6]. This is why prompt diagnosis and aggressive management of acute osteomyelitis are critical to the prognosis and final outcome^[20].