Not a Radiological sign of Perthe’s disease
**Core Concept**
Perthe's disease, also known as Legg-Calve-Perthes disease, is a childhood hip disorder characterized by avascular necrosis of the femoral head. It typically affects children between the ages of 4 and 10. The condition is often diagnosed through radiological imaging, which reveals specific signs indicative of the disease.
**Why the Correct Answer is Right**
The correct answer is related to the radiological findings associated with Perthe's disease. The disease is characterized by a "crescent sign" or "crescent-shaped" area of subchondral bone resorption, which is visible on radiographs. This sign is a result of the collapse of the subchondral bone due to the loss of blood supply to the femoral head. Additionally, the "flake-like" fragmentation of the femoral head is also a common radiological finding.
**Why Each Wrong Option is Incorrect**
* **Option A:** Not a radiological sign of Perthe's disease. This option is incorrect because the "sclerosis sign" is actually a radiological sign associated with Perthe's disease, indicating the presence of reactive bone formation in response to the avascular necrosis of the femoral head.
* **Option B:** Not a radiological sign of Perthe's disease. This option is incorrect because the "cystic change" sign is also a radiological finding associated with Perthe's disease, indicating the presence of cystic lesions in the femoral head.
* **Option C:** Not a radiological sign of Perthe's disease. This option is incorrect because the "fragmentation sign" is actually a radiological sign associated with Perthe's disease, indicating the presence of flake-like fragmentation of the femoral head.
* **Option D:** Not a radiological sign of Perthe's disease. This option is incorrect because the "bone infarct sign" is actually a radiological sign associated with Perthe's disease, indicating the presence of a bone infarct in the femoral head.
**Clinical Pearl / High-Yield Fact**
A key radiological finding in Perthe's disease is the "crescent sign," which is indicative of subchondral bone resorption due to the collapse of the subchondral bone. This sign is often visible on radiographs and is essential for diagnosing the condition.
**Correct Answer: D. Bone infarct sign is a radiological sign of Perthe's disease.**