Which radiographic finding is most indicative of chronic osteomyelitis?

Which radiographic finding is most indicative of chronic osteomyelitis?

• A. Periosteal reaction without lucency
• B. Subacute bone sclerosis
• C. Sequestrum with involucrum on imaging
• D. Normal radiographs

Answer: (C)

The main idea is that chronic osteomyelitis leaves a distinctive pattern on X-ray: dead bone that has become separated from living bone (a sequestrum) surrounded by new bone laid down by the periosteum (an involucrum). The sequestrum is the radiopaque fragment of necrotic bone, and the involucrum appears as a shell of reactive bone around it. This combination is strongly indicative of long-standing infection, reflecting both bone death and the body's attempt to isolate it.

In contrast, acute osteomyelitis often shows early periosteal reaction and soft-tissue changes, but not the established sequestrum and involucrum. Subacute bone sclerosis can occur in various chronic conditions and is less specific, and normal radiographs do not indicate chronic disease. So the presence of a sequestrum with involucrum on imaging is the clearest indicator of chronic osteomyelitis.