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.

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.

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.

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
  
  

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• 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)

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

There are a number of treatment options for osteomyelitis. The type of therapy depends on the nature and severity of the infection. Treatments include:

• Antibiotics. Osteomyelitis caused by a bacterial infection is treated with intravenous antibiotics to keep acute osteomyelitis from becoming chronic. In the case of hematogenous osteomyelitis, this treatment may last from two to six weeks. Once the condition has been better controlled, oral antibiotics may be prescribed. In some cases, scraping and irrigation of the bone (debridement) may be considered. The rise of drug-resistant bacteria such as MRSA (methicillin-resistant Staphylococcus aureus) has complicated treatment.
  
  
• Drainage. Pockets of fluid surrounding infected bone (abscesses) may be drained with a needle.
  
  
• Surgery. If the infection already has progressed to the chronic stage, it is often necessary to remove the dead bone through a surgical procedure. Surgery to remove necrotic tissue and improve circulation can prevent extensive amputation later. Once the bone has been removed, it is replaced by a graft or packing material designed to promote the growth of new bone tissue. The patient is likely to remain on antibiotics for at least three weeks after surgery.
  
  
• Hyperbaric (high-pressure) oxygen. Some medical centers offer hyperbaric chambers as an option. High-pressure pure oxygen may promote healing by increasing circulation.  

Orthopedic prosthetics can also lead to infection. Metal surfaces provide an area where the bacteria adhere and multiply as biofilm. The biofilm shields germs from the body’s defenses and antibiotic treatment. It may therefore be necessary to surgically remove the prosthesis and the infected tissue surrounding the area. In some cases, a new prosthesis may be implanted immediately. In cases where the infection is more severe, implantation of the prosthesis may be delayed.

When osteomyelitis is detected early, the prognosis is good. With timely and appropriate treatment, acute osteomyelitis is curable. However, the outlook is much less favorable in cases of chronic osteomyelitis. This is especially true for patients with poor blood circulation due to conditions such as diabetes or peripheral artery disease. In such cases, amputation is frequently necessary.

Complications that may continue with osteomyelitis even after treatment include:

• Progression of acute to chronic osteomyelitis
• Local spread of infection
• Reduced limb or joint function

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?