Osteomyelitis

Osteomyelitis is a pyogenic bone infection that may be chronic or acute. The disease commonly results from combined traumatic injury - usually minor but severe enough to cause a hematoma - and acute infection originating elsewhere in the body. Osteomyelitis usually remains a local infection, but it can spread through the bone to the marrow, cortex, and periosteum.

Acute osteomyelitis is typically a blood-borne disease that most often affects rapidly growing children, particularly boys. Multiple draining sinus tracts and metastatic lesions characterize the rarer chronic osteomyelitis. The incidence of both types of osteomyelitis is declining, except in drug abusers.

In children, the most common disease sites include the lower end of the femur and the upper end of the tibia, humerus, and radius. In adults, the disease commonly localizes in the pelvis and vertebrae and usually results from contamination related to surgery or trauma.

The prognosis for a patient with acute osteomyelitis is good if he receives prompt treatment. The prognosis for a patient with chronic osteomyelitis (more prevalent in adults) is poor.

Causes

Osteomyelitis is usually caused by bacteria, most commonly Staphylococcus aureus. But many other bacteria, including TB, may be to blame and occasionally fungal infections occur. Osteomyelitis is usually due to spread of micro-organisms through the blood but sometimes is the result of spread of infection from a nearby wound.

Signs and Symptoms

Osteomyelitis usually starts suddenly. Symptoms include the following:

•  fever, 
•  severe pain around the bone that is affected, 
•  swelling and redness at the joints next to the bone. The joints may also feel very tender, 
•  nausea,
• fatigue, and 
•  a general feeling of being unwell.

Diagnostic tests

White blood cell (WBC) count shows leukocytosis if the patient has osteomyelitis and the erythrocyte sedimentation rate increases.

Blood culture can be used to identify the pathogen.

X-rays may show bone involvement only after the disease has been active for some time, usually 2 to 3 weeks.

Bone scans can be used to detect early infection. Computed tomography scanning and magnetic resonance imaging may be necessary to determine the extent of infection.

Diagnosis must rule out poliomyelitis, rheumatic fever, myositis, and bone fractures.

Treatment

To decrease internal bone pressure and prevent infarction, treatment for acute osteomyelitis begins even before confirming the diagnosis. After drawing samples for blood culture, high doses of I.V. antibiotics are typically administered; usually, a penicillinase-resistant agent, such as nafcillin or oxacillin, is administered. The infected site may be drained surgically to relieve pressure and remove sequestrum. The infected bone is usually immobilized with a cast or traction, or by complete bed rest. The patient receives analgesics and LV. fluids as needed.

If an abscess forms, treatment includes incision and drainage, followed by a culture of the drainage. Anti-infective therapy may include systemic antibiotics; intracavitary instillation of antibiotics through closed-system continuous irrigation with low intermittent suction; limited irrigation with a blood drainage system equipped with suction such as a Hemovac; or local application of packed, wet, antibiotic-soaked dressings.

Some patients may receive hyperbaric oxygen therapy to increase the activity of naturally occurring WBCs. Additional measures include using free tissue transfers and local muscle flaps to fill in dead space and increase blood supply.

Chronic osteomyelitis may also require surgery: sequestrectomy to remove dead bone and saucerization to promote drainage and decrease pressure. The typical patient reports severe pain and requires prolonged hospitalization. Unrelieved chronic osteomyelitis in an arm or a leg may require amputation.

Prevention

Prompt and complete treatment of infections is helpful. High-risk people should see a health care provider promptly if they have signs of an infection anywhere in the body.