A 7-year-old boy sustained an open compound fracture of the right tibia and fibula in a fall from a barn loft to the floor below. On physical examination, the lower tibia and fibula can be seen protruding from the lower leg. The fracture is set by external manipulation, and the skin wound is sutured, but nothing more is done. One year later, he continues to have pain in the right leg, and a draining sinus tract has developed in the lateral lower right leg. A radiograph of the lower right leg is now most likely to show which of the following?

This patient has chronic osteomyelitis. The most likely sequence of events is the occurrence of a compound fracture that became infected by direct extension of bacteria into the bone. The subsequent care for this patient was inadequate, and he developed chronic osteomyelitis. Infection of the bone and the associated vascular compromise caused bone necrosis, giving rise to a dead portion of the bone, called a sequestrum. With chronicity, a shell of reactive new bone, called involucrum, is formed around the dead bone. A nidus with surrounding sclerosis suggests an osteoid osteoma. Osteolysis and osteosclerosis are features of bone remodeling with Paget disease of bone. Soft-tissue hemorrhage and swelling should be minimal and resolve soon after the fracture is stabilized. A mass suggests a malignancy, and the most common neoplasm to develop in a sinus tract draining from osteomyelitis is squamous cell carcinoma, but this is uncommon.