What is the most common cause of chronic osteomyelitis in adults?

• A. Open injury or recent surgery
• B. Hematogenous spread from a distant infection
• C. Chronic viral infection
• D. Vascular malformation

Answer: (B)

In adults, chronic osteomyelitis most often starts from contiguous spread of infection from a nearby focus, such as after an open injury, penetrating trauma, or recent surgery. This pathway allows bacteria to seed bone directly and persist, especially when local tissue is damaged or vascular supply is compromised. Hematogenous spread is more typical in children and is a well-known cause of vertebral osteomyelitis in adults, but it accounts for fewer chronic adult cases overall. The other options don’t fit the usual infectious mechanism.