Osteomyelitis is an infection and inflammation of the bone or the bone marrow. It can happen if a bacterial or fungal infection enters the bone tissue from the bloodstream, due to injury or surgery.
Around 80 percent of cases develop because of an open wound.
Bone infections commonly affect the long bones in the leg and upper arm, the spine, and the pelvis.
In the past, it was difficult to treat osteomyelitis, but now, aggressive treatment can often save the infected bone and stem the spread of infection.
Osteomyelitis is estimated to affect 2 out of every 10,000 people in the United States at some time.
Contents of this article:
Signs and symptoms
Pain, redness, and swelling can be a sign of a bone infection.
The signs and symptoms of osteomyelitis depend on the type.
They commonly include:
- Pain, which can be severe, and swelling, redness, and tenderness in the affected area
- Irritability, lethargy, or fatigue
- Fever, chills, and sweating
- Drainage from an open wound near the infection site or through the skin
Other symptoms may include swelling of the ankles, feet, and legs, and changes in walking pattern, for example, a limp.
The symptoms of chronic osteomyelitis are not always not obvious, or they could resemble the symptoms of an injury.
This can make accurate diagnosis more difficult, especially in the hip, pelvis, or spine.
Osteomyelitis in children and adults
In children, osteomyelitis tends to be acute, and it usually appears within 2 weeks of a pre-existing blood infection. This is known as hematogenous osteomyelitis, and it is normally due to methicillin-resistant Staphylococcus aureus (S. aureus) (MRSA).
Diagnosis can be difficult, but it is important to get a diagnosis as soon as possible, because delaying diagnosis can lead to growth disturbances or deformity. It can be fatal.
In adults, sub-acute or chronic osteomyelitis are more common, especially after an injury or trauma, such as a fractured bone. This is known as contiguous osteomyelitis. It usually affects adults over the age of 50 years.
Types of osteomyelitis
There are three main types of osteomyelitis.
Acute osteomyelitis: Infection develops within 2 weeks of an injury, initial infection, or the start of an underlying disease. The pain can be intense, and the condition can be life-threatening.
Sub-acute osteomyelitis: Infection develops within 1 to 2 months of an injury, initial infection, or the start of an underlying disease.
Chronic osteomyelitis: infection starts at least 2 months after an injury, initial infection, or the start of an underlying disease.
Risk factors and causes
Some people are more likely to experience osteomyelitis.
People at higher risk may have:
- A weakened immune system, due, for example, to chemotherapy or radiation treatment, malnutrition, dialysis, having a urinary catheter, injecting illegal drugs, and so on
- Circulatory problems, as a result of diabetes, peripheral arterial disease, or sickle cell disease
- A deep puncture wound or a fracture that breaks the skin
- Surgery to replace or repair bones
Acute osteomyelitis is more common in children, while the spinal form is more common in patients aged over 50 years, and it is more common in males.
Osteomyelitis can occur when a bacterial or fungal infection develops within a bone or reaches the bone from another part of the body.
A tooth infection can spread to the jaw bone.
When an infection develops inside the bone, the immune system will try to kill it. Neutrophils, a type of white blood cell, will be sent to the source of the infection to kill the bacteria or fungus.
If the infection takes hold and is not treated, dead neutrophils will accumulate inside the bone, forming an abscess, or pocket of pus.
The abscess may block vital blood supplies to the affected bone. In chronic osteomyelitis, the bone may eventually die.
Bones are normally resistant to infection, but infection may enter a bone under certain conditions.
An infection in the bloodstream, complications of trauma or surgery, or pre-existing conditions, such as diabetes, reduce the person's ability to resist infection.
How bone infections start
Bone infections can occur in different ways.
In hematogenous osteomyelitis, the infection may start as a mild upper respiratory or urinary tract infection, for example, and travel through the bloodstream. This type is more common in children.
Post-traumatic osteomyelitis may occur after a compound fracture, a broken bone that breaks the skin, an open wound to surrounding skin and muscle, or after surgery, especially if metal pins, screws or plates are used to secure broken bones.
Vascular deficiency, or poor blood circulation, can cause infection to develop from a minor scrape or cut, usually on the feet. Poor circulation prevents white blood cells from reaching the site, leading to deep ulcers. These expose the bone and deep tissue to infection.
Vertebral osteomyelitis occurs in the spine. It usually starts with an infection in the bloodstream, a urinary or respiratory tract infection, endocarditis, which is an infection in the inner-lining of the heart, or an infection in the mouth or at an injection site.
Osteomyelitis of the jaw
Osteomyelitis of the jaw can be intensely painful, and it can result from caries or periodontal disease. The jawbone is unusual because the teeth provide a direct entry point for infection.
A sinus, gum, or tooth infection can spread to the skull.
Diagnosis, treatment, and complications
The physician will examine the affected body part for signs of osteomyelitis, including tenderness and swelling. They will ask about recent medical history, especially any recent accidents, operations, or infections.
Tests may include:
- Blood tests: High levels of white blood cells usually indicate infection.
- Biopsy: The physician takes a small piece of tissue to test which type of pathogen - bacteria or fungi - is causing bone infection. This helps find a suitable treatment.
- Imaging tests: An x-ray, MRI, or CT scan can reveal any bone damage.
The damage may not be visible for 2 weeks on an X-ray, so more detailed MRI or CT scans are recommended if the injury is recent.
Treatment depends on the type of osteomyelitis.
A course of antibiotics or antifungal medicine is normally effective. For adults, this is usually a 4- to 6-week course of intravenous, or sometimes oral, antibiotics or antifungals. Some patients need treatment in hospital, while others may receive injections as an outpatient, or at home if they can inject themselves.
Possible side effects from antibiotics include diarrhea, vomiting, and nausea. Sometimes there may be an allergic reaction.
If the infection is caused by MRSA or some other drug-resistant bacteria, the patient may need a longer course of treatment and a combination of different medications.
In some cases, hyperbaric oxygen therapy (HBOT) may be recommended.
Treatment depends on severity, and whether there is any bone damage.
If there is no bone damage, treatment is similar to that used in acute osteomyelitis, but If there is bone damage, treatment will be similar to that used in chronic osteomyelitis.
Patients usually need both antibiotics and surgery to repair any bone damage.
Surgery can involve:
- Draining: The area around the infected bone may need opening up for the surgeon to drain any pus or fluid that has built up in response to the infection.
- Debridement: The surgeon removes as much diseased bone as possible, and takes a small margin of healthy bone to ensure that all the infected areas are removed. Any surrounding tissue with signs of infection may also need removing.
- Restoring blood flow to the bone: Any empty space left by debridement may have to be filled with a piece of bone tissue, or skin or muscle from another part of the body. Temporary fillers can be used until the patient is healthy enough for a bone or tissue graft. The graft helps the body repair damaged blood vessels, and it will form new bone.
- Removal of foreign objects: If necessary, foreign objects placed during previous surgery may be removed, such as surgical plates or screws.
- Stabilizing the affected bone: Metal plates, rods, or screws may be inserted into the bone to stabilize the affected bone and the new graft. This may be done later. Occasionally external fixators are used to stabilize the affected bone.
If the patient cannot tolerate surgery, for example, because of illness, the doctor may use antibiotics for longer, possibly years, to suppress the infection. If the infection continues regardless, it may be necessary to amputate all or part of the infected limb.
Successful treatment of the infection is normally possible, but sometimes complications occur.
Chronic osteomyelitis can appear to have gone, but then it resurfaces, or it may persist undetected for years. This can lead to bone tissue death and the collapse of the bone.
People with conditions that are difficult to treat, such as severe diabetes, HIV, poor circulation, or a weakened immune system are more at risk.
Patients with a weakened immune system should:
Cleaning and dressing an open wound can prevent infection.
- Have a well-balanced healthy diet and suitable exercise, to boost the immune system
- Avoid smoking, as this weakens the immune system and contributes to poor circulation
- Practice good hygiene, including regular and proper handwashing
- Have all the recommended shots
Patients with poor circulation should:
- Avoid smoking, as it worsens the circulation
- Maintain a healthy body weight by following a healthy diet
- Exercise regularly to improve your circulation
- Avoid excessive regular alcohol consumption as this raises the risk of hypertension, or high blood pressure, and high cholesterol
People who are susceptible to infections should be especially careful to avoid cuts and scrapes. Any cuts or scrapes should be cleaned at once, and a clean dressing put over it.
Wounds need frequent checking for signs of infection.