Osteomyelitis -Causes, Signs and symptoms

Osteomyelitis

Also called: Chronic Osteomyelitis, Acute Osteomyelitis

Summary

Osteomyelitis is an inflammation of bone due to infection. The infection can be acute or chronic and is usually bacterial.

Risk factors for osteomyelitis include traumatic injury, diabetes, an impaired immune system, atherosclerosis, sickle cell anemia, bone surgery, hemodialysis and intravenous drug abuse. Signs and symptoms can include pain, swelling and fatigue.

Acute osteomyelitis is curable. In the early stages, treatment usually involves extended doses of intravenous and oral antibiotics. If the condition progresses to chronic osteomyelitis, however, it becomes extremely dangerous. Surgical removal of the infected bone or amputation of a limb may be necessary.

People help avoid osteomyelitis by practicing good hygiene and safety habits and by preventing or controlling the disorders that increase its risk.

About osteomyelitis

Osteomyelitis is inflammation of the bone caused by an infection, usually from bacteria but sometimes from fungi. Left untreated, it may progress to a severe infection and gangrene that may require surgical removal of bone or amputation of a limb.

The infection that leads to osteomyelitis usually can be traced to one of two sources:

  • The bloodstream. An infection from somewhere in the body travels through the bloodstream to bone in another area.
  • Direct injury. An injury such as a puncture wound, an animal bite or an open fracture from a car accident directly infects nearby bone.

When a bone is initially infected, the condition is known as acute osteomyelitis. An infected bone is likely to be filled with pus that collects in an abscess. This abscess prevents the blood from reaching the bone. If acute osteomyelitis is left untreated and continues over a long period of time, it can progress to chronic osteomyelitis, which may result in the death of the bone tissue (osteonecrosis). Once the tissue in the bone is dead, cells sent by the immune system cannot reach the infection to combat it.

Chronic osteomyelitis can impair the patient’s ability to use a limb or joint, and can spread to other parts of the body. Eventually, an infected bone may force amputation of a limb. Chronic osteomyelitis of the spine is particularly dangerous and has the potential to damage the nerves. In rare cases, osteomyelitis can even be fatal.

The bones most often infected in osteomyelitis differ depending on a person’s age. In children, long bones are most often affected. These bones, such as the femur (thigh bone), are longer than they are wide. Adults are most likely to experience osteomyelitis in the vertebrae (spinal bones) and the pelvis. They are also at increased risk of malignant external otitis, a severe ear infection that can spread to the skull and jawbone.

Types and differences of osteomyelitis

There are two main forms of osteomyelitis:

  • Acute osteomyelitis. An infection that involves the bone’s periosteum (dense fibrous membrane covering the surface of bones) or cortical bone and medullary cavity (marrow cavity in the shaft of a long bone). This disease is more common in children than adults, and more common in boys than girls. 

  • Chronic osteomyelitis. A case of acute osteomyelitis that becomes recurring or that is not resolved. Chronic osteomyelitis can spread to other parts of the body if left untreated.

    Types of chronic osteomyelitis include:

    • Medullary. The endosteum (thin layer of cells lining the medullary cavity) is infected.

    • Superficial. Surrounding soft tissue that does not heal. Cortex (outer layer of the bone) and periosteum are infected.

    • Combined localized. Both the medulla (inner core of the bone) and the cortex are infected. A fistula (abnormal passage resulting from an injury) may be present.

    • Combined diffuse. Similar to combined localized, with the addition that the bone and limb are both unstable.

Risk factors and potential causes of osteomyelitis

Osteomyelitis is usually caused by a bacterial infection. Often it is due to Staphylococcus aureus, but it can also involve other bacteria (e.g., Streptococcus, Pseudomonas Salmonella), or a fungus. S. aureus is an increasing concern because of growing spread in recent years of drug-resistant forms known as MRSA (methicillin-resistant Staphylococcus aureus).

The infection reaches the bone in one of two ways:

  • Contiguous spreading osteomyelitis. Usually starts with a bacterial infection of the skin, such as a diabetic foot ulcer, before progressing into nearby bone. This is the more common form of osteomyelitis. Other sources of injury that can directly infect the bone include puncture wounds, animal bites, traffic or factory accidents and damage inadvertently caused by surgery. Surgery to remove infected bone is often necessary, along with a long regimen of intravenous and oral antibiotics.
  • Hematogenous osteomyelitis. Begins with microorganisms that infect the skin, urinary tract or another area. This infection eventually enters the bloodstream and travels to bone, often located away from the original infection site. Children usually experience hematogenous osteomyelitis in a long bone of a leg or arm. Adults are more likely to suffer infection in the spine.

    Hematogenous osteomyelitis can often be treated and controlled with four to six weeks of intravenous antibiotics, followed by a course of oral antibiotics. In some cases, surgery to remove infected bone may be necessary.

Osteomyelitis is more common in men, children and elders. Other factors that increase the risk of developing it include:

  • Trauma to skin and bones, such as deep cuts, fractures or damage caused by cancer or radiation therapy

  • Diabetes or other conditions that impair blood circulation, such as atherosclerosis or high blood pressure

  • Hemodialysis (a method of removing impurities or wastes from the blood when the kidneys are unable to do so) or use of other medical devices such as a urinary catheter or central line

  • Intravenous drug abuse

  • Chronic infections of the skin, urinary tract or other areas

  • Orthopedic surgery, including implants of prosthetics such as hip or knee replacements

  • Conditions that impair the immune system, such as AIDS, removal of the spleen or use of immunosuppressive medications

  • Sickle cell anemia (genetic disorder that results in abnormal blood cells)

Signs and symptoms of osteomyelitis

Symptoms that may accompany osteomyelitis include:

  • Nagging pain in the bone that worsens with movement
  • Sudden, intense bone pain when touching the area
  • Swelling, redness and warmth at the site
  • Fatigue
  • Fever
  • Nausea
  • General feeling of malaise
  • Drainage of pus through the skin
  • Excessive perspiration
  • Chills
  • Low back pain
  • Swelling (edema) of the ankles, feet and legs
  • Unexplained weight loss

Diagnosis methods for osteomyelitis

In diagnosing osteomyelitis, a physician will review the patient’s medical history and perform a physical examination. The physician may look for signs of bone tenderness, swelling (edema), redness and warmth.

In addition, the physician will distinguish potential infection of the bone (osteomyelitis) from infection of the joint (septic arthritis). In the latter, no movement is possible at the joint, whereas in the former, minimal function of the adjacent joint remains. A patient can have both conditions.

Other techniques may be used to diagnose osteomyelitis or determine the type of organism responsible for the infection. These tests include:

  • X-ray. This may reveal the location and extent of infection in the bone.

  • Bone scan, MRI (magnetic resonance imaging), CAT scan (computed axial tomography) or ultrasound. These imaging techniques may provide more detail if x-rays are insufficient.

  • Bone biopsy. A local anesthetic is administered before tissue is removed from the bone. It is easiest to obtain samples from bones close to the skin. Cultures are performed on the sample to confirm an infection and pinpoint its cause.

  • Blood tests, such as: 

    • Complete blood count (CBC). An elevated number of white blood cells indicates infection.

    • Erythrocyte sedimentation rate (ESR). This test of the red blood cells can indicate infection or inflammation.

    • MRI and needle aspiration (drawing of blood). This may be performed in the area around the infected bone so a culture may be done.

    • Blood culture. This blood test can be used to identify the type of organism responsible for the infection.

Prevention methods for osteomyelitis

People can help prevent osteomyelitis by avoiding staph and other infections. Methods include:

  • Frequent hand washing
  • Not sharing personal items such as towels and razors
  • Making sure that healthcare workers wash their hands and use gloves
  • Using antibiotics only as directed

It also helps to reduce the risk of injuries with commonsense methods such as using seatbelts, wearing bicycle and motorcycle helmets and practicing good workplace safety. Prompt treatment of any wound or infection is important.

Patients can also reduce the risk of bone infection by taking steps that maintain good circulation or otherwise promote good health. These include:

  • Quitting smoking

  • Avoiding intravenous drug abuse

  • Preventing or controlling diabetes, high blood pressure, atherosclerosis and other risk factors for impaired circulation

  • Performing routine foot care and skin care and receiving foot exams from a physician, particularly for those with conditions such as diabetes

  • Taking precautions against or controlling immune disorders, such as HIV infection, allergies, asthma and lupus

Questions for your doctor on osteomyelitis

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about osteomyelitis:

  1. Could I have, or am I at risk of developing, osteomyelitis?

  2. What tests for osteomyelitis might I need to undergo, and what do they involve?

  3. What caused my osteomyelitis?

  4. Is my osteomyelitis acute or chronic?

  5. What are my treatment options, and which do you recommend?

  6. What is the expected course of my condition?

  7. Could my osteomyelitis require surgery or amputation? Is there anything I can do to prevent the need for this?

  8. How can I reduce my risk of developing or redeveloping osteomyelitis?

  9. Do I need to improve my diet and exercise habits? Do I need to improve control of my glucose, blood pressure, cholesterol or anything else?

  10. Should I have periodic foot exams from a doctor? What kind of skin care and foot care should I perform at home?
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