Inflammatory lesions.

Most cases of osteomyelitis are of bacterial origin and staphylococci are the most common agent. Anaerobic osteomyelitis is much less common. In most cases, infection originates in another site and spreads directly from post-traumatic or operative infections. A proportion of osteomyelitis patients suffer from peripheral vascular disease, especially diabetes. Approximately 20% of cases are haematogenous, with skin, urinary and respiratory infections thought to predispose to osteomyelitis. Although acute haematogenous osteomyelitis may occur at any age, patients are usually under 15 years old. The long bones are those most commonly affected.