Acute Pyogenic Osteomyelitis eMedicine Radiology

Description: Acute osteomyelitis is an inflammation of bone caused by an infecting organism. Staphylococcus aureus is the most common bacterium involved in the infection.
On the basis of the route of infection, acute osteomyelitis can be classified as hematogenous or exogenous. Hematogenous osteomyelitis is predominantly seen in children and involves the highly vascular long bones, especially those of the lower limb. In adults, hematogenous spread is more common to the lumbar vertebral bodies than elsewhere.
Before puberty, infection starts in the metaphyseal sinusoidal veins. Because bones are relatively rigid structures, focal edema accumulates under pressure and leads to local tissue necrosis, breakdown of the trabecular bone structure, and removal of bone matrix and calcium. Infection spreads along the haversian canals, through the marrow cavity, and beneath the periosteal layer of the bone. Subsequent vascular damage causes the ischemic death of osteocytes, leading to the formation of a sequestrum. Periosteal new-bone formation on top of the sequestrum is known as involucrum.
Osteomyelitis may be acute, subacute, or chronic. With acute osteomyelitis, the presenting complaint is usually local pain, swelling, and warmth. These often occur with associated fever and malaise.
Synonyms and related keywords: acute osteomyelitis, subacute osteomyelitis, chronic osteomyelitis, bone inflammation, hematogenous osteomyelitis, exogenous osteomyelitis