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?

## **Core Concept**
The question revolves around the complications arising from an open compound fracture, specifically focusing on the development of a draining sinus tract, which is highly suggestive of **osteomyelitis**. Osteomyelitis is an infection of the bone, which can occur as a complication of an open fracture due to direct inoculation of bacteria into the wound.

## **Why the Correct Answer is Right**
The development of a draining sinus tract in the context of a previous open compound fracture is highly indicative of chronic osteomyelitis. Chronic osteomyelitis often presents with **sequestra** (dead bone fragments) and **involucrum** (new bone formation around the sequestra). A radiograph in such cases is most likely to show **sequestra**, which are characteristic of chronic osteomyelitis. Sequestra appear as areas of dense, dead bone that have become separated from the living bone as a result of the infectious process.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option does not directly relate to the expected findings in chronic osteomyelitis. Without a description, we infer it's incorrect based on the context not matching chronic osteomyelitis radiographic findings.
- **Option B:** Similarly, this option does not describe findings typical of chronic osteomyelitis. The presence of a draining sinus and pain suggests a more chronic and complicated process than what might be implied here.
- **Option C:** While this could potentially represent some form of bone pathology, it does not specifically suggest chronic osteomyelitis or the presence of sequestra and involucrum.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that the presence of a draining sinus tract in a patient with a history of trauma (such as a fracture) is highly suggestive of osteomyelitis until proven otherwise. Radiographic findings of sequestra and involucrum are diagnostic of chronic osteomyelitis. Remember, **sequestra** are a hallmark of chronic osteomyelitis on radiographs.

## **Correct Answer:** . **Sequestra**.

✓ Correct Answer: B. Involucrum and sequestrum