What Is Osteomyelitis? What Causes Osteomyelitis?

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Main Category: Bones / Orthopedics
Also Included In: Infectious Diseases / Bacteria / Viruses;  Blood / Hematology
Article Date: 10 Feb 2010 - 0:00 PDT

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Osteomyelitis means infection of the bone or bone marrow; inflammation of the bone due to infection. Osteomyelitis sometimes occurs as a complication of injury or surgery. In some cases, the infection may get into bone tissue from the bloodstream. Patients with osteomyelitis typically experience deep pain and muscle spasms in the inflammation area, as well as fever.

Osteomyelitis is usually caused by a bacterial infection. In some cases, a fungal infection may be the cause.

Bone infections commonly affect the leg and upper arm bones, as well as the spine and pelvis - the long bones.

There are three types of osteomyelitis:

• Acute osteomyelitis - the infection develops within two weeks of an injury, initial infection, or the start of an underlying disease.
• Sub-acute osteomyelitis - the infection develops within one or two months of an injury, initial infection, or the start of an underlying disease.
• Chronic osteomyelitis - the bone infection starts at least two months after an injury, initial infection, or the start of an underlying disease.

In children osteomyelitis generally occurs as an acute condition, usually developing as a complication of a pre-existing blood infection (hematogenous osteomyelitis). In adults, sub-acute or chronic osteomyelitis are more common, usually caused by an injury or trauma (contiguous osteomyelitis), such as a fractured bone.

Osteomyelitis can usually be effectively treated today. This was not the case many years ago. Aggressive treatment is required to save the infected bone, as well as stemming the spread of the infection.

According to the National Health Service (NHS), UK, acute osteomyelitis is uncommon in children; of whom approximately 1 in every 1,000 is affected during childhood. Only 1 in every 5,000 children over the age of 1 year develops osteomyelitis in the UK.

The NHS adds that accurate data on adults is more limited. It is known to be a common complication of some health conditions. Approximately 30% to 40% of patients with diabetes who experience a puncture injury to the foot subsequently develop osteomyelitis. Osteomyelitis affects 1 in every 200 patients in the UK with sickle cell anemia each year.

According to Medilexicon's medical dictionary:

Osteomyelitis is "Inflammation of the bone marrow and adjacent bone"

What are the signs and symptoms of osteomyelitis?

A symptom is something the patient feels and reports, while a sign is something other people, such as the doctor detect. For example, pain may be a symptom while a rash may be a sign.

The signs and symptoms of osteomyelitis may vary, depending on the type.

Signs and symptoms of acute osteomyelitis:

• Affected area of bone is painful
• Affected area of bone is tender
• Affected area of bone is warmer than other areas
• Affected area of bone may be red
• Elevated body temperature (fever), which may be abrupt. Sometimes not present. In children may be mild.
• Sometimes there is loss of movement in the affected area
• Young children may be irritable or lethargic

Signs and symptoms of sub-acute and chronic osteomyelitis:

• Affected area is tender
• Affected area may be red
• Affected area may look strange, possibly deformed
• Bone pain in the affected area
• Chronic fatigue
• Instability in the affected area
• Loss of movement in the affected area
• Near the area of infection there may be drainage from an open wound

Sometimes the symptoms of chronic osteomyelitis may be subtle (not obvious), or they could be symptoms of an injury, rather than an infection. When identifiable signs and symptoms are not present inside the hip, pelvis or spine, an accurate diagnosis is much more difficult.

What are the risk factors for osteomyelitis?

A risk factor is something which increases the likelihood of developing a condition or disease. For example, obesity significantly raises the risk of developing diabetes type 2. Therefore, obesity is a risk factor for diabetes type 2.

• Gender - bone infection occurs more commonly in males than females.
• Age - acute osteomyelitis is more common in children, while the spinal form is more common in patients aged over 50 years.
• Infection risk - people who are at a higher risk of infections also have a higher risk of developing osteomyelitis. Examples include individuals who illegally inject drugs, patients on dialysis, patients with urinary catheters, some patients with weakened immune systems.
• Patients with circulation problems - for example, people with diabetes, peripheral arterial disease and sickle cell disease have a higher risk of developing osteomyelitis.
• Injuries - anybody who had a deep puncture wound, or a broken bone that broke the skin has an increased risk of developing osteomyelitis.
• Bone surgery (orthopedic surgery) - any surgery that repairs bones or replaces joints carries a risk of osteomyelitis.

What are the causes of osteomyelitis?

A bacterial or fungal infection can develop within a bone or reach the bone from another part of the body.

When an infection develops inside the bone, our 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 neutrophoils will accumulate inside the bone, forming an abscess (pocket of pus). The abscess may block vital blood supplies to the affected bone. If the osteomyelitis is chronic (long-term) the bone may eventually die.

Our bones are generally resistant to infection. However, sometimes a bacterial or fungal infection may infect bone, in one of the following ways:

• A pre-existing blood infection may spread to a bone.
• A bone fracture, some injury, or a complication of orthopedic surgery may result in a bone infection.
• The bone infection may be caused by a pre-existing condition, such as diabetes. In such cases, the supply of blood to the bone is undermined; specifically white blood cells (which fight infection).

Bone infections are divided into several types, including:

• Hematogenous osteomyelitis - the infection travels through the bloodstream. Most children with osteomyelitis get this type; it is much less common in adults. A mild infection may develop somewhere in the body, such as the upper respiratory tract or urinary tract, and spread through the bloodstream and eventually infect a bone.
• Post-traumatic osteomyelitis - these are bone infections that occur after trauma, such as a compound fracture (broken bone that breaks the skin), or an open wound to surrounding skin and muscle. According to The Mayo Clinic, USA, this type of bone infection can also develop after surgery, especially if metal pins, screws or plates are used to secure broken bones.
• Vascular deficiency - people with poor blood circulation may develop an infection from a seemingly minor scrape or cut, usually on the feet. As their circulation is poor, infection-fighting white blood cells cannot get to the infection site in sufficient numbers. A deep ulcer may develop, exposing the bone and deep tissue to infection.
• Vertebral osteomyelitis - this is osteomyelitis that occurs in the spine. It usually starts with an infection in the bloodstream, but can also be the result of surgery or trauma. It generally affects older patients. The original infection may have been a urinary tract infection, respiratory tract infection, endocarditis (infection in the inner-lining of the heart), mouth infection, or an infection at an injection site.

Diagnosing osteomyelitis

The GP (general practitioner, primary care physician) will carry out a physical examination of the affected body part, checking for signs of osteomyelitis, which include tenderness and swelling. The patient will be asked about his/her recent medical history, whether there have been any recent accidents, operations, or infections.

The following tests may be ordered:

• Blood tests - if levels of white cells are higher than normal it usually means that there is some kind of infection. This test may also determine what type of germ is present. However, a blood test in itself cannot determine whether a patient has osteomyelitis.
• X-rays - these may determine what bone damage there is (if any). Often bone damage is not visible in an X-ray until several weeks after the onset of osteomyelitis. If the infection has developed recently, more detailed imaging tests may be required.
• MRI (magnetic resonance imaging) or CT (computerized tomography) scans - if the X-rays are not clear enough, the doctor may order an MRI or CT scan.
• Biopsy - a small piece of infected bone is removed by a surgeon and analyzed in a laboratory. This test can tell what type of pathogen (bacteria or fungi) is causing the bone infection. This helps determine what treatment to pursue. Alternatively, the doctor may insert a long needle into the bone and take a biopsy (fine needle aspiration).

What are the treatment options for osteomyelitis?

Acute osteomyelitis - in most cases a course of antibiotics or antifungal medicines effectively treats the osteomyelitis. Adults usually need a 4 to 6 weeks course of oral or intravenous antibiotics/antifungals (usually intravenous) - in some cases patients have to take antibiotics for much longer. Some patients may need to be hospitalized during treatment, while others may receive injections at outpatients, or at home if they are taught how to inject themselves. There is a risk of side effects from antibiotics, including diarrhea, vomiting and/or nausea. Sometimes there may be an allergic reaction.

If the infection is caused by MHRA, or some other drug-resistant bacteria, the patient may need a longer course of treatment, as well as a combination of different medications.

Children usually need to start on intravenous medications, and may subsequently be able to switch to oral ones if they respond well to treatment.

Sub-acute osteomyelitis - treatment depends on infection severity and whether there has been any bone damage.

If there is no bone damage treatment is similar to that used in acute osteomyelitis.

If there is bone damage, treatment will be similar to that used in chronic osteomyelitis.

Chronic osteomyelitis - patients usually require antibiotics as well as surgery to repair any bone damage.

• Draining the infected area - the area around the infected bone may have to be opened up so that the surgeon can drain any pus or fluid that has built up in response to the infection.
• Debridement - the surgeon removes whatever diseased bone he/she can, as well as taking a small margin of healthy bone to make sure that all the infected areas are removed. Any surrounding tissue that has signs of infection may also have to be removed.
• Restoring blood flow to the bone - any empty space left by the debridement procedure may have to be filled with a piece of bone tissue, or skin or muscle from another part of the body. In some cases, temporary fillers are used until the patient is healthy enough for a bone or tissue graft. The graft helps the body repair damaged blood vessels, as well as forming 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 need to be inserted into the bone to stabilize the affected bone and the new graft. Sometimes this is done at a later date. Occasionally external fixators are used to stabilize the affected bone.

If the patient cannot tolerate surgery because they are very ill and could not endure the procedure and recovery, the doctor may use antibiotics for longer - in some cases even years - to suppress the infection. If the infection continues regardless it may be necessary to amputate all or part of the infected limb.

What are the possible complications of osteomyelitis?

In most cases the infection that caused osteomyelitis can be effectively treated and controlled.

• Recurring chronic osteomyelitis - osteomyelitis that comes back or persists undetected for years is known as chronic osteomyelitis. Chronic osteomyelitis can sometimes result in bone tissue death and the collapse of the bone. The underlying factors that cause this type of osteomyelitis, such as severe diabetes, HIV, poor circulation or a weakened immune system may be difficult to treat.
  
  For patients who have had a previous episode of chronic osteomyelitis, there is a risk of recurrence.
• Amputation - patients whose health is very poor and are not able to undergo surgery may eventually need to have a foot, leg, or arm amputated if the infection spreads.

Preventing osteomyelitis

Patients with a weakened immune system

• A well-balanced healthy diet will help optimize the immune system.
• Don't smoke. Not only does it further weaken the immune system, but also contributes to poor circulation.
• Hygiene - regular and proper handwashing helps protect people from infection.
• Make sure you have taken all your shots.
• Regular exercise helps improve the immune system. Check what exercises you can do with your doctor or a qualified physical therapist (UK: physiotherapist).

Patients with poor circulation

• Don't smoke. Smoking worsens your circulation.
• Diet - a healthy, well-balanced diet will help clear your arteries and maintain a healthy bodyweight, both of which will help optimize your circulation.
• Exercise - regular exercise will improve your circulation, among other things. Check what exercises you can do with your doctor or a qualified physical therapist (UK: physiotherapist).
• Alcohol - excessive regular alcohol consumption raises the risk of hypertension (high blood pressure) as well as high cholesterol levels. If you drink, make sure it is in moderation.

Cuts and scrapes

• Take precautions to avoid cuts and scrapes, especially if you know you are vulnerable to infection.
• If you do have a cut or scrape, clean the area straight away and place a clean bandage over it.
• Check wounds often for any sign of infection.

Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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