Osteomyelitis: what is it, causes, symptoms and treatment, complications and prognosis

What is osteomyelitis?

Osteomyelitis is an infection of the bone, most often caused by bacteria, less commonly by other types of pathogens that often reach the bone through the blood. Osteomyelitis can be acute or chronic and is defined as such primarily on the basis of the pathological pattern of the tissue, rather than the duration of the infection. The most common cause of osteomyelitis, acute or chronic, is Staphylococcus aureus in both children and adults.

When the bone is infected, it often develops swelling of the soft interior (bone marrow). The swollen inner part begins to press against the hard outer wall of the bone, leading to crushing blood vessels in the bone marrow, as a result of which blood flow to the bone is reduced or stops.

Without sufficient blood supply, bone tissue may die. Infections of these dead areas of bone tissue are difficult to treat, because these areas are not penetrated by the body's natural cells that specialize in protecting against infections, as well as antibiotics.

The infection can also spread beyond the bone and lead to pus-filled lumps (abscesses) in nearby soft tissues, such as muscle tissue. Abscesses sometimes break through the skin on their own.

Classification

There are two types of osteomyelitis, which are more differentiated in relation to the bone profile than in the duration of the infection itself:

• Acute osteomyelitisassociated with inflammatory changes in the bones caused by pathogenic bacteria, the symptoms of which usually appear two weeks after infection.
• Chronic osteomyelitis represents bone necrosis, that is, the death of a part of the bone tissue.

Further classifications of osteomyelitis are based on the putative mechanism of infection: for example, if it is transmitted through blood or as a result of direct penetration of bacteria into the bone due to infection of adjacent soft tissues or open wounds.

Osteomyelitis causes

Osteomyelitis is caused by various infectious agents. When the bone marrow (the soft tissue inside the bone) becomes infected, it swells and puts pressure on the blood vessels in the bone, causing them to collapse. The microorganisms found differ depending on the age of the patients:

• Bacteria Staphylococcus aureus (Staphylococcus aureus) are the most common cause of acute and chronic osteomyelitis in adults and children.
• Group A streptococcus (Pneumococcus and K. kingae) are the other two most common pathogens in children.
• Streptococcal infections group B found mainly in newborns.
• In adults, Staphylococcus aureus is the most common bone pathogen associated with prosthetic infections.
• Other possible microorganisms: Staphylococcus epidermidis, Pseudomonas aeroginosa, Serratia marcescens and Escherichia coli.
• Besides, fungal and mycobacterial infections have also been reported in patients with osteomyelitis, but they remain rare and usually occur in patients with impaired immune function (immunodeficiency).
• There are rare cases parasitic infection (echinococcosis).
• In the context trauma infection is very often associated with several microorganisms.

The mechanism of action that causes chronic osteomyelitis is as follows: bacteria adhere to the bone and form a biofilm in which they become less sensitive not only to the patient's immune system, but also to antibiotics.

At the macroscopic level, inflammation creates areas of bone necrosis (dead tissue) when it clogs up the channels of the blood vessels. These areas of dead bone without vascularization are called "sequesters".

People most susceptible to disease

Staphylococcus aureus often affects hospitalized people, which is why it is called nosocomial infections - a microbe that infects a patient as a result of his hospitalization or visiting a medical institutions. Thus, a Staphylococcus aureus infection can infect a person during the insertion of a catheter, prosthesis, or probe.

People most at risk for acute osteomyelitis are children, who are more likely to be affected by growth of areas of long bones that are highly vascularized and subject to even minor injuries. More than half of cases of acute hematogenous (blood borne) osteomyelitis in children occur in patients under the age of five. In contrast, chronic osteomyelitis in children is very rare.

Risk factors

Risk factors, namely predisposition to osteomyelitis, are mainly:

• type 2 diabetes;
• peripheral vascular disease.

As these conditions progress, the incidence of chronic osteomyelitis in the population increases.

Osteomyelitis symptoms

Symptoms of acute osteomyelitis:

• fever (high temperature);
• irritability;
• local erythema (redness);
• edema;
• the sensitivity of the infected bone.

Chronic osteomyelitis symptoms:

• often secondary to open fractures;
• chronic pain;
• poor wound healing;
• general malaise;
• sometimes fever.

Osteomyelitis symptoms can be nonspecific and difficult to recognize. Identification of the bacterial infection in question is not always easy, since blood cultures that detect them are positive only in half of the cases.

Complications

Major complications of osteomyelitis include:

• Bone death (osteonecrosis). Bone infection can obstruct blood circulation inside the bone, resulting in death. For antibiotics to work, the dead bone must be surgically removed.
• Septic arthritis. Sometimes, an infection in the bones can spread to nearby joints.
• Poor growth. If osteomyelitis occurs in soft tissues called growth plates at either end of the long bones of the arms or legs, it can affect the normal growth of the bones and joints in children.
• Skin cancer. If osteomyelitis has an open wound that secretes pus, there is a high chance that squamous cell carcinoma will develop on the surrounding skin.

Diagnostics

Osteomyelitis can be suspected based on symptoms and physical examination. For example, doctors may suspect osteomyelitis in a patient with persistent pain in a specific area of ​​the bone, accompanied or not accompanied by fever, presenting with complaints of almost constant fatigue.

If doctors suspect osteomyelitis, they do blood tests to check for inflammation, looking for one of the following:

• sedimentation rate of erythrocytes (ESR is an analysis that measures the rate at which erythrocytes settle to the bottom of a test tube with blood);
• level C-reactive protein (the protein circulating in the blood rises sharply in case of inflammation).

Elevated ESR and C-reactive protein levels usually indicate inflammation. In addition, an increase in the white blood cell count is often found in the blood test results. However, the results of such blood tests are not sufficient to diagnose osteomyelitis, although the results in within the normal range, indicating little or no inflammation, reduce the likelihood osteomyelitis.

X-rays can detect the characteristic signs of osteomyelitis, but in some cases this is possible only 2-4 weeks after the first symptoms appear.

Computed tomography (CT) or magnetic resonance imaging (MRI) is done if the x-ray results are questionable or if symptoms are severe. CT and MRI scans can identify infected areas or joints and detect infections in adjacent tissues, such as abscesses.

Alternatively, you can do a bone scan (imaging the bones after injection with an injection of a substance called radioactive technetium). Infected areas almost always appear altered on bone scans, with the exception of bones in children of the first year of life, since scans do not always reliably indicate deviations in the growing bones. However, a scan may not always distinguish an infection from other bone diseases. Leukocyte scan (images obtained after intravenous injection of leukocytes treated with radioactive indium) allows you to distinguish infection from other diseases in areas that look altered on scans bones.

Doctors may take samples of blood, pus, synovial fluid, or the bone tissue itself to diagnose a bone infection and identify pathogenic organisms. Typically, for osteomyelitis of the spine, bone samples are removed with a needle or during surgery.

Osteomyelitis treatment

Antibiotics are the most effective treatment for children and adults who have recently had a bone infection that has spread through the bloodstream. If it is not possible to determine the bacterium that causes the infection, antibiotics are used that are effective against Staphylococcus aureus and many other types of bacteria (broad spectrum antibiotics). Depending on the severity of the infection, antibiotics may be given by vein (intravenously) for 4–8 weeks. Then they switch to taking antibiotics by mouth for a longer period of time, depending on the patient's response to them. Some people with chronic osteomyelitis may be treated with antibiotics for several months.

If a fungal infection is found or suspected, treatment with antifungal drugs is necessary for several months. If the infection is detected early, surgery is usually not required.

In adults with bacterial vertebral osteomyelitis, antibiotic therapy usually lasts 4 to 8 weeks. Bed rest is sometimes necessary and the patient may need to wear a corset. For draining abscesses or strengthening the affected vertebrae (in order to prevent vertebrae from crushing and, as a result, nearby nerves, spinal column, or blood vessels) may require surgery intervention.

If osteomyelitis develops due to an infection of nearby soft tissues, the complexity of treatment increases. Surgery is usually performed to remove dead tissue and bone, and the resulting cavities are filled with healthy skin or other tissue. The infection is then treated with antibiotics. Broad-spectrum antibiotics must be taken more than 3 weeks after surgery.

If an abscess is present, surgery is usually required to remove it. Also, surgery is indicated for patients with persistent fever and weight loss.

Forecast

In treatment, the clinical outcome of acute osteomyelitis is generally good.

The prognosis is disappointing for people with long-term (chronic) illness. Symptoms can come and go over the years, even with surgery. Amputation may be required, especially in people with diabetes or poor circulation.

The prognosis for people with prosthetic infection depends in part on:

• human health;
• type of infection;
• whether the infected prosthesis can be removed without problems.

Can osteomyelitis be prevented?

The easiest way to prevent osteomyelitis is to keep your skin clean. All cuts and wounds, especially deep ones, must be thoroughly cleaned. Moisten wounds with soap and water and keep them under running water for at least five minutes in a row to rinse them thoroughly and remove any dirt.

To keep the wound clean after rinsing, cover it with sterile gauze or a clean cloth. You can apply a healing over-the-counter antibacterial cream to the wound, but most importantly, keep it well cleaned. Wounds should begin to heal within the first 24 hours and completely heal within a week.

A wound that takes longer to heal and / or that causes severe pain should be examined by a specialist.

And, as with many infections, parents and children should wash their hands thoroughly and frequently to prevent the spread of germs. Children should also receive the necessary vaccinations in a timely manner.