Which imaging method is recommended if hip asymmetry is noted in an infant under 6 months?

In infants under 6 months, the recommended imaging method for evaluating hip asymmetry is hip ultrasound. This is primarily due to the presence of cartilaginous structures in the developing hip joint, which are not well visualized with X-rays. Ultrasound is a superior choice because it is non-invasive, does not involve radiation, and can effectively assess the acetabulum and femoral head for any signs of developmental dysplasia or other abnormalities.

In this age group, X-rays may not provide adequate information since the bones are still developing and may not be fully ossified. Similarly, a CT scan is generally avoided in young children due to higher radiation exposure and the necessity for sedation in many cases. MRI is also not commonly used in this context due to its higher costs, the complexity of acquiring images in infants, and the limited specific diagnostic advantage it offers over ultrasound. Thus, hip ultrasound is the most appropriate and effective method for assessing hip asymmetry in infants under 6 months.