Question

In a child with suspected developmental dysplasia of the hip (DDH), what is the investigation of choice?

• A. X-ray
• B. MRI
• C. USG
• D. CT scan

Hint:

The infant hip is mostly cartilage and the bony nucleus has not ossified yet.

Answer 1

The Correct Option is C

Step 1: Developmental dysplasia of the hip (DDH) is a spectrum of abnormal hip development seen in infants. Early detection is critical, so the imaging chosen must reliably show the infant hip.

Step 2: In a young infant, the femoral head and acetabulum are largely cartilaginous and not yet ossified. Ultrasonography (USG) is the investigation of choice because it directly visualizes the cartilaginous femoral head and acetabulum and permits dynamic real-time assessment (Barlow and Ortolani-type maneuvers) of hip stability.

Step 3: Why the other options are wrong: X-ray is unhelpful in early infancy because the ossific nucleus of the femoral head usually appears only around 4 to 6 months, so the cartilage is invisible (X-ray becomes useful in older children once ossification occurs). MRI and CT are not first-line in an infant; MRI is costly and often needs sedation, and CT adds ionizing radiation without offering a dynamic study.

Step 4: Hence USG, being radiation-free, dynamic, and able to image cartilage, is the correct answer.