Which one of the following is the investigation of choice for evaluation of suspected Perthes’ disease?
**Core Concept**
Perthes' disease, also known as Legg-Calve-Perthes disease, is a childhood hip disorder characterized by the temporary loss of blood supply to the femoral head, leading to its necrosis. The condition typically affects children between the ages of 4 and 10 years. The evaluation of suspected Perthes' disease involves assessing the extent of femoral head involvement and monitoring the progression of the disease.
**Why the Correct Answer is Right**
Magnetic Resonance Imaging (MRI) is the investigation of choice for evaluating suspected Perthes' disease because it provides detailed images of the cartilage and bone marrow, allowing for early detection of femoral head necrosis and assessment of the extent of involvement. MRI can also help in identifying the stage of the disease, which is essential for planning treatment and predicting the outcome. The MRI protocol should include T1-weighted images for assessing the morphology of the femoral head and T2-weighted images for detecting marrow edema.
**Why Each Wrong Option is Incorrect**
**Option A:** Plain radiographs, while useful for initial assessment, may not detect early changes of Perthes' disease and may require multiple follow-up visits to demonstrate progression.
**Option B:** Computed Tomography (CT) scans can provide detailed images of the bone but are not the preferred modality for assessing the marrow and cartilage changes associated with Perthes' disease.
**Option C:** Arthrography involves injecting a contrast agent into the joint space and may not provide adequate visualization of the femoral head and surrounding bone marrow.
**Clinical Pearl / High-Yield Fact**
In children with suspected Perthes' disease, a delay in diagnosis and treatment can lead to a worse outcome, emphasizing the importance of early and accurate diagnosis.
**Correct Answer:** C. MRI.