Osteomyelitis

Osteomyelitis is a pyogenic bone infection that may be chronic or acute. The disease commonly results from a combination of traumatic injury 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 caused by hematogenous spread that most commonly affects rapidly growing children, particularly boys. Multiple draining sinus tracts and metastatic lesions characterize the rarer chronic osteomyelitis, which is more prevalent in adults.

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 or she receives prompt treatment. The prognosis for patients with chronic osteomyelitis is poor.

Causes

Infection causes osteomyelitis. Bacterial pyogens are the most common agents, but the disease may also result from fungi or viruses. The most common pyogenic organisms are Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa, Haemophilus influenzae, and Enterobacter species. Typically, these organisms find a site of local infection and spread through the blood directly to bone. As the organisms grow and produce pus within the bone, pressure builds within the rigid medullary cavity and forces the pus through the haversian canals. A subperiosteal abscess forms, depriving the bone of its blood supply and eventually causing necrosis. In turn, necrosis stimulates the periosteum to create new bone (involucrum). The old, dead bone (sequestrum) detaches and works its way out through either an abscess or the sinuses. By the time the body processes sequestrum, osteomyelitis is chronic.

Complications

Osteomyelitis may lead to chronic infection, skeletal deformities, joint deformities, disturbed bone growth (in children), differing leg lengths, and impaired mobility.

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