Which one of the following is the investigation of choice for evaluation of suspected Pehes’ disease?
**Core Concept**
Pehes' disease, also known as Perthes disease, is a childhood hip disorder characterized by the breakdown of the blood supply to the femoral head, leading to necrosis and collapse of the bone. The investigation of choice should ideally provide a clear visualization of the femoral head and surrounding structures.
**Why the Correct Answer is Right**
Magnetic Resonance Imaging (MRI) is the investigation of choice for evaluating suspected Perthes' disease. It provides high-resolution images of the hip joint, allowing for the assessment of the femoral head, articular cartilage, and surrounding soft tissues. MRI can detect early changes in the femoral head, including marrow edema, bone marrow infarction, and cartilage abnormalities, which are indicative of Perthes' disease. The detailed imaging of MRI enables accurate diagnosis, assessment of disease severity, and monitoring of treatment response.
**Why Each Wrong Option is Incorrect**
**Option A:** X-ray is not the primary investigation for Perthes' disease because it may not detect early changes in the femoral head and can be normal in the early stages of the disease. X-ray is more useful for detecting late-stage changes, such as subchondral cysts and sclerosis.
**Option B:** CT scan is not the preferred investigation for Perthes' disease because it provides less detail of the soft tissues compared to MRI. While CT scan can detect bony changes, it is not as sensitive as MRI for detecting early marrow edema and cartilage abnormalities.
**Option C:** Ultrasound is not suitable for evaluating Perthes' disease because it provides limited information about the hip joint and surrounding structures. Ultrasound is more useful for assessing soft tissue abnormalities and guiding injections.
**Clinical Pearl / High-Yield Fact**
MRI is the investigation of choice for Perthes' disease due to its high sensitivity and specificity for detecting early changes in the femoral head and surrounding soft tissues.
**Correct Answer:** C. MRI.