Osteomyelitis

Introduction

Osteomyelitis is a medical term that describes an infection of bone. The infection is usually bacterial. Symptoms of osteomyelitis may include:

• high temperature (fever) of 38°C (100.4°F) or above
• pain in the affected area, which can often be intense
• swelling in the affected area 
• a passageway that opens in the skin through which pus or fluid leaks (this is known as a discharging sinus)

Types of osteomyelitis

There are two main types of osteomyelitis:

• Acute osteomyelitis is where the bone infection develops within two weeks of an initial infection, injury or underlying disease and may respond to antibiotic treatment.
• Chronic osteomyelitis is where the bone infection has produced irreversible bony changes that cannot be treated by antibiotics alone.

Acute osteomyelitis

There are two ways that acute osteomyelitis can occur:

• Contiguous osteomyelitis is where an infection spreads directly into the bone as a result of an injury, such as a fractured bone or animal bite, during surgery, or as a result of another condition such as diabetes or vascular disease.
• Haematogenous osteomyelitis is where an infection spreads into a bone from the bloodstream.

Contiguous osteomyelitis is the most common type of acute osteomyelitis, accounting for four out of five cases. It mainly affects adults.

People who have a condition that affects the blood supply to certain parts of their body, such as type 2 diabetes, have an increased risk of developing contiguous osteomyelitis. Any surgical procedure on the skeleton may introduce infection into bone.

Haematogenous osteomyelitis mostly affects younger children, although adult cases may occur in anyone with a weakened immune system, such as those with rheumatoid arthritis or HIV.

People who regularly inject drugs, such as heroin, also have an increased risk of developing haematogenous osteomyelitis.

Chronic osteomyelitis

Chronic osteomyelitis can sometimes start as acute osteomyelitis. If acute osteomyelitis is not treated properly it can become established and produce permanent, destructive changes to bone, resulting in pain, discharge and loss of function.

As with acute osteomyelitis, the infection can be spread through the blood or directly into the bone as a result of injury or other trauma.

Chronic osteomyelitis can also develop as a complication of a pre-existing infection such as tuberculosis (a bacterial infection) or syphilis (a sexually transmitted infection).

How common is osteomyelitis?

At present, there are limited data on how widespread osteomyelitis is in adults.

Acute osteomyelitis is rare in children. It is estimated that one child in every 1,000 children under the age of one, and one in every 5,000 over the age of one will develop acute osteomyelitis.

The condition is known to be a common complication of certain health conditions. For example:

• 30-40% of people with diabetes who experience a puncture injury to their foot will develop osteomyelitis
• One in every 200 people with sickle cell anaemia (a hereditary blood condition) will develop osteomyelitis in any given year

Outlook

The outlook for acute osteomyelitis is generally good because the condition usually responds well to antibiotics. However, for people with underlying risk factors for osteomyelitis, such as diabetes, there is a chance that the infection could come back.

The outlook for chronic osteomyelitis is mixed because the infection can be more challenging to treat, particularly if significant bone damage has occurred. Most cases will require a combination of antibiotics and surgery.

Symptoms of osteomyelitis

Acute osteomyelitis

Most cases of acute osteomyelitis involve one of the long bones in the legs. However, sometimes the bones in the arm or the vertebrae (in the back) can be affected.

The symptoms of acute osteomyelitis include:

• A sudden high temperature (fever) of 38°C (100.4°F) or above, although this symptom is often absent in children under one year old
• Bone pain, which can often be severe
• Swelling, redness and warmth at the site of the infection
• A general sense of feeling unwell
• The affected body part is tender to touch
• The range of movement in the affected body part is restricted
• Lymph nodes (glands) near the affected body part may be swollen

Young children who cannot talk may be unable to report their painful symptoms to you. You should look out for the following signs and symptoms:

• Irritability
• Eating much less than usual
• Reluctance to use the affected body part

Chronic osteomyelitis

Once chronic osteomyelitis is established, the person affected may have periods of almost no symptoms. However, symptoms can flare up at any time. For example, you may experience:

• Bone pain
• Feeling persistently tired
• Pus draining from the sinus tract (a passageway that develops near the infected bone)
• Local swelling
• Skin changes
• Excessive sweating
• Chills

When to seek medical advice

You should always visit Dr. B C Shah if you or your child develops a high temperature (fever) and persistent bone pain.

Causes of osteomyelitis

Routes of infection

Your bones are usually resistant to infection. Bone can become infected when:

• A pre-existing infection in the blood spreads to a bone
• There is an injury, such as a bone fracture, or a complication from a surgical procedure
• There is a pre-existing health condition, such as diabetes, which means the bone does not get a steady blood supply, so infection-fighting white blood cells cannot reach the site of injury

Blood infections that spread to the bone are more common in children than adults. This may be because children’s bones are still developing, which makes them more vulnerable to this type of blood-borne infection than adult bones, which are fully grown.

In addition, a child's immune system (the body’s natural defence against infection and illness) is still developing, so it is less effective than an adult’s at fighting off infection.

When a bone becomes infected

When an infection develops inside a bone, the immune system will attempt to stop it by sending infection-fighting white blood cells known as neutrophils to the source of the infection.

The neutrophils will try to kill the bacterial or fungal cells that are causing the infection, but sometimes they are unable to do so. If the infection is not treated, a collection of dead neutrophils will build up inside the bone, forming a pocket of pus known as an abscess.

In cases of chronic osteomyelitis, abscesses can block the blood supply to the bone, which will eventually cause the bone to die. Dead bone with no blood supply must be removed if infection is to be cleared.

Risk factors

There are several risk factors that can make people more vulnerable to developing osteomyelitis. They include:

• Weakened immune system
• Poor circulation
• Diabetes and foot injury
• Injury and trauma
• Orthopaedic surgery
• Intravenous drug use

These risk factors are described below.

Weakened immune system

If your immune system is weakened, it is more likely that an infection that develops in one part of your body will spread to a bone. Your immune system may become weakened for any of the following reasons:

• You have a health condition, such as HIV or AIDS
• You are taking certain treatments, such as chemotherapy, radiotherapy or a long-term dose of steroid tablets
• You have malnutrition, which is when your diet does not contain all the nutrients needed for good health

Poor circulation

People with health conditions that affect the blood flow are at greater risk of developing osteomyelitis. This is because their bones may not be getting a steady supply of infection-fighting white blood cells.

Conditions that are known to cause poor circulation include:

• Type 1 diabetes and type 2 diabetes
• Sickle cell anaemia, which is an inherited blood disorder where the red blood cells do not function properly
• Atherosclerosis, which is narrowing of the arteries, often caused by eating a high-fat diet and/or smoking
• Peripheral arterial disease, which is where the main arteries in the legs get clogged up by a build-up of fat

Diabetes and foot injury

People with diabetes are particularly vulnerable to osteomyelitis because they are at risk of developing foot injuries.

Increased levels of glucose in the blood can cause nerve damage. This means that people with poorly controlled diabetes may begin to lose sensation in their feet so small cuts or injuries to the feet go unnoticed. Due to poor circulation, a serious infection can quickly develop in the feet before spreading to the bone.

Injury and trauma

If you break a bone or have a serious puncture injury that exposes deep tissue to germs, there is a chance you will develop osteomyelitis. This risk is increased if you also have a weakened immune system and/or poor circulation. Any broken bone with a loss of skin cover needs emergency surgery to clean the wound, get rid of dead tissue and stabilise the fracture. 

Orthopaedic surgery

If you have orthopaedic surgery (surgery that involves the bones or joints) or you have had metalwork implanted, there is a small chance you may develop osteomyelitis. The risk is less than 1%.

Intravenous drug misuse

People who regularly inject themselves with illegal drugs such as heroin or methamphetamine (crystal meth) have an increased risk of developing osteomyelitis. This is because many people who misuse drugs do not use properly sterilised needles, which significantly increases the risk of introducing bacteria into their bloodstream. 

Diagnosing osteomyelitis

Physical examination

To confirm a diagnosis of suspected osteomyelitis, Dr. B C Shah will first carry out a physical examination of your affected body part to check for signs of redness, swelling and tenderness.

They will want to know about your recent medical history, such as whether you have recently had an injury, surgery or a previous infection.

Blood test

Dr. B C Shah may refer you for a blood test. This cannot confirm osteomyelitis, but it can indicate whether you have a high number of white blood cells in your blood, which may suggest that you have an infection. Also, if the osteomyelitis was caused by bacteria spreading in your blood, a blood test may be useful for detecting the bacteria.

Imaging tests

If osteomyelitis is suspected, it is likely that you will be referred for further imaging testing. There are several imaging tests that may be able to detect bone damage caused by osteomyelitis. They include:

• X-rays, in which low levels of radiation are used to create an image of the affected bone
• Magnetic resonance imaging (MRI) scan, which is where a strong magnetic field and radio waves are used to build up a picture of the inside of the affected bone
• Computerised tomography (CT) scan, which is where a series of X-rays of your affected bone are taken and a computer is used to assemble them into a more detailed three-dimensional image
• Ultrasound scan, which is where high-frequency sound waves are used to create an image of the affected bone to highlight any abnormalities

Biopsy

If earlier testing suggests that you have osteomyelitis, it is usually necessary to remove a small sample of bone for further testing. This is known as a biopsy.

A biopsy is usually necessary to confirm a diagnosis of osteomyelitis and it can help to establish the exact type of bacteria or fungus that is causing your infection. This can be very useful when deciding on the most effective treatment.

A biopsy is usually combined with surgery in chronic cases.

Treating osteomyelitis

Treating acute osteomyelitis

Acute osteomyelitis can usually be successfully treated using antibiotics

These medicines are usually given as a six-week course. For part of the treatment course you will need to take the medicine intravenously (directly into a vein). 

Depending on your general state of health, you may need to stay in hospital during this time. Otherwise, you may be able to receive the injections as an outpatient (where you go home the same day). You will usually be able to switch to tablets for the rest of the treatment course once you are well.

In cases of osteomyelitis, there is usually a choice of antibiotics available to treat the infection and often two antibiotics are used in combination. This is known as dual therapy.

Occasionally, the bacteria causing the infection are resistant to standard antibiotics and less-frequently-used antibiotics are needed.

All antibiotics have side effects, which you should discuss with Dr. B C Shah in charge of your care.

A much less common cause of osteomyelitis is a fungal infection.

In cases of fungal osteomyelitis, an antifungal medication called voriconazole is usually the treatment of choice. 

Treating chronic osteomyelitis

People with chronic osteomyelitis will usually require a combination of antibiotics medication and surgery to remove any damaged bone. Dr. B C Shah may need to make an incision (cut) near the site of the infection to drain away any pus.

If there is extensive bone damage, it will be necessary to surgically remove any diseased bone and tissue. This procedure is known as debridement. Debridement can often leave an empty space in the bone, which is sometimes packed with antibiotic-loaded cement. If Dr. B C Shah does this, a second operation will be required to remove the cement within a few weeks of the first. Not all centres use cement and no difference is found in the clearance of infection.

In some cases, it may also be necessary to transfer muscle and skin from another part of the body to repair the tissue surrounding the affected bone.

Hyperbaric oxygen therapy

Some researchers have argued that a type of non-surgical treatment called hyperbaric oxygen therapy may be useful in treating cases of both acute and chronic osteomyelitis that do not respond to conventional treatment.

During hyperbaric oxygen therapy, you are placed in a specially designed chamber that is similar to a decompression chamber used by divers.

The chamber is filled with oxygen, which is administered at a much higher pressure (hyperbaric) than the normal level of oxygen in the atmosphere. The high levels of oxygen are thought to speed up the healing process and slow the spread of infection.

There is currently only limited evidence supporting the effectiveness of hyperbaric oxygen therapy for treating osteomyelitis. From the evidence available, it would appear that it is most effective in treating osteomyelitis associated with a diabetic foot ulcer. 

Complications of osteomyelitis

Recurring osteomyelitis

The underlying factors that often cause osteomyelitis, such as poor circulation or a weakened immune system, can be difficult to treat, particularly if you have severe diabetes or HIV. Therefore, if you have had a previous episode of osteomyelitis, there is a chance that it could return.

The risk factors for recurring osteomyelitis vary depending on your circumstances. It may be possible to reduce your risk by making lifestyle changes, such as lowering the amount of saturated fat in your diet and by taking precautions against infection.

Amputation

Amputation is sometimes necessary when someone has a condition, such as diabetes or peripheral vascular disease, that affects the normal blood supply to parts of their body. With a reduced blood supply, the affected body part will receive fewer infection-fighting blood cells. This means that the infection may spread beyond the bone and into the surrounding soft tissue. The tissue will then begin to die, which is known as gangrene.

Once gangrene develops, it is sometimes necessary to amputate the affected limb to prevent the spread of infection and prevent further damage to healthy tissue.

Preventing osteomyelitis

If you have a weakened immune system, take extra precautions to avoid infection and boost your immune system:

• Do not smoke, because it will weaken your immune system.
• Keep your vaccinations up to date. Dr. B C Shah will be able to advise you about this.
• Eat a healthy diet to help boost your immune system.
• Take regular exercise to help boost your immune system.
• Wash your hands regularly with soap and hot water, particularly after going to the toilet, before and after preparing food and after being in crowded places.

If you have poor circulation, avoid activities that could make it worse, such as smoking. Some lifestyle changes will also help to improve your circulation, such as taking regular exercise.

Stop smoking (if you smoke)

Smoking cigarettes can clog up your arteries and increase your blood pressure, both of which are bad for your circulation.

If you smoke, it is strongly recommended that you quit as soon as possible. Dr. B C Shah will be able to recommend and prescribe medication that can help you give up.

Eat a healthy diet

High fat foods can cause a build-up of fatty plaques (deposits) in your arteries, and being overweight can lead to high blood pressure.

To improve your circulation, a low-fat high-fibre diet is recommended, including plenty of fresh fruit and vegetables (at least five portions a day) and wholegrains.

It is also recommended that you eat a Mediterranean-style diet. This means you should eat more bread, fruit, vegetables and fish and less meat. Replace butter and cheese with products that are vegetable and plant-oil based, such as olive oil.

Oily fish is recommended as it contains a type of fatty acid called omega-3, which can help lower your cholesterol levels. This can help to improve your circulation. Two to four portions of oily fish a week are recommended. Good sources of omega-3 include:

• Herrings
• Sardines
• Mackerel
• Salmon
• Trout
• Tuna

If you are unable or unwilling to eat oily fish, Dr. B C Shah may recommend that you take an omega-3 food supplement. However, you should never take a food supplement without first consulting him. This is because some supplements, such as beta-carotene, can be harmful.

Weight management

If you are overweight or obese, try to lose weight and then maintain a healthy weight by using a combination of a calorie-controlled diet and regular exercise. Once you have achieved a healthy weight it will help keep your blood pressure at a normal level, which will help improve your circulation.

Alcohol

If you drink alcohol, don't exceed the recommended daily limits. These are:

• Three to four units a day for men
• Two to three units a day for women

A unit of alcohol is roughly half a pint of normal-strength beer, a small glass of wine or a single measure (25ml) of spirits. Regularly exceeding the recommended alcohol limits will raise both your blood pressure and cholesterol level, which will make your circulation worse.

Contact Dr. B C Shah if you are finding it difficult to moderate your drinking. Counselling services and medication can help you to reduce your alcohol intake.

Regular exercise 

Regular exercise will lower your blood pressure and make your heart and blood circulatory system more efficient.

For most people, 30 minutes of moderate to vigorous exercise a day, at least five times a week, is recommended. However, if your overall health is poor, it may be necessary for you to exercise using a programme that is tailored specifically to your current needs and fitness level. Dr. B C Shah will be able to advise you about the most suitable level of exercise for you.

Activities that you could incorporate into your exercise programme include:

• Brisk walking
• Hill climbing
• Running
• Cycling
• Swimming

If you find it difficult to achieve 30 minutes of exercise a day, start at a level that you feel comfortable with. For example, you could do 5 to 10 minutes of light exercise a day before gradually increasing the duration and intensity of your activity as your fitness starts to improve.