Which of the following is/are X ray feature/s of pehes disease?
**Core Concept**
Pehes disease, also known as Perthes disease, is a childhood hip disorder characterized by the loss of blood supply to the femoral head, leading to its necrosis and deformation. The disease is associated with alterations in the normal hip joint structure and function.
**Why the Correct Answer is Right**
The X-ray features of Perthes disease include a classic "crescent sign" and a "subchondral fracture line." The crescent sign is a radiolucent area in the lateral aspect of the femoral head, indicating the loss of bone density and bone marrow edema. The subchondral fracture line is a horizontal or oblique line of demarcation, representing a fracture through the subchondral bone. These changes are due to the avascular necrosis of the femoral head, which disrupts the normal bone architecture and leads to the characteristic X-ray findings.
**Why Each Wrong Option is Incorrect**
* **Option A:** Osteosclerosis is the hardening of bone, which is not a characteristic feature of Perthes disease. In fact, the disease is associated with bone softening and decreased density.
* **Option B:** Joint space narrowing is a feature of degenerative joint diseases, such as osteoarthritis, rather than Perthes disease.
* **Option C:** Coxa vara is a deformity of the hip joint, characterized by a shortening of the femoral neck, which is not a direct result of Perthes disease.
**Clinical Pearl / High-Yield Fact**
Perthes disease often presents with hip pain and limited mobility in children, and a thorough radiographic evaluation is essential for diagnosis. The disease can lead to long-term consequences, including joint deformities and osteoarthritis, if not properly treated.
**Correct Answer: C. Coxa vara is a deformity of the hip joint, characterized by a shortening of the femoral neck, which is not a direct result of Perthes disease.