Osteomyelitis

Infection, inflammation, and destruction of bone caused by microorganisms.

The incidence increases in persons > 50. Infection reaches bone via the blood stream (hematogenous osteomyelitis) or by spread from adjoining tissue (contiguous osteomyelitis).

Hematogenous osteomyelitis most often affects the vertebrae but may also affect the long bones (eg, femur, tibia, humerus). About 60% of vertebral osteomyelitis cases occur in persons > 50. Generally, only one organism is isolated, most commonly Staphylococcus aureus; however, gram-negative aerobic bacilli, most likely due to genitourinary tract infection or to instrumentation, are also frequently found.

Contiguous osteomyelitis is due to septic foci that usually result from postoperative infections, pressure sores, diabetic ulcers, radiation therapy, or foreign bodies. Mixed bacteria are often found, frequently S. aureus, S. epidermidis, gram-negative aerobic bacilli, and anaerobic species.

Vascular insufficiency (eg, due to diabetes, atherosclerosis, or vasculitis) and neuropathy are common contributing factors to osteomyelitis of the foot in elderly patients. The small bones of the feet and toes are most often involved. Mixed bacteria are commonly found, including S. aureus, S. epidermidis, streptococci, gram-negative aerobic bacilli, and anaerobic organisms.

Symptoms, Signs, and Diagnosis

Pain is the hallmark symptom of osteomyelitis. However, pain may be absent in debilitated patients with osteomyelitis due to an overlying pressure sore that does not heal and in diabetic patients with osteomyelitis of the foot. Fever may be absent. The ESR is almost always elevated, but leukocytosis is variable.

Early-stage osteomyelitis is diagnosed by a technetium bone scan or MRI. Advanced osteomyelitis can be diagnosed by x-ray. Biopsy of bone may be necessary to determine the causative organism and its sensitivity to antibiotics.

Treatment

Antibiotics may be required for weeks to months. Although such treatment is best started in the hospital, it can be provided (orally or intravenously) at home using home health services. The choice of antibiotic should be based on organisms grown from blood cultures or on deep bone biopsy findings; cultures of superficial bone or overlying wounds often produce inaccurate results. While cultures are being processed, before the results are known, broad-spectrum antibiotics covering staphylococci and gram-negative organisms should be given. Debridement is also frequently needed.