[Imaging in hip disorders in childhood and adolescence].

backgroundHip disorders in childhood and adolescence require precise imaging to prevent maldevelopment, deformities, and early osteoarthritis. ULTRASOUND: Ultrasound is the primary first-line modality: radiation-free, dynamic, and indispensable in infancy. It provides detailed assessment of cartilaginous and soft-tissue structures and is essential in developmental dysplasia of the hip (DDH) to evaluate maturation and femoral head centration. It also enables rapid detection of joint effusions in transient synovitis or septic arthritis, as well as inflammatory changes in juvenile idiopathic arthritis (JIA). In addition, ultrasound offers useful early clues in Legg-Calvé-Perthes disease and slipped capital femoral epiphysis (SCFE). RADIOGRAPHY: From about 6 months of age, radiography becomes central to evaluating the bony anatomy. Standard projections such as the anteroposterior pelvic view and the frog-leg lateral view allow reliable assessment of acetabular morphology, femoral head position, and head-neck geometry. MAGNETIC RESONANCE IMAGING: Magnetic resonance imaging (MRI) is the most comprehensive cross-sectional technique. It expands diagnostic capabilities in Perthes disease, SCFE, inflammatory conditions, and tumors, and provides detailed visualization of cartilage, the labrum, bone marrow edema, and torsional alignment. Modern fast sequences enable short, focused examinations in young children, often without the need for sedation. COMPUTED TOMOGRAPHY: Computed tomography (CT) is reserved for specific indications and is valuable for analyzing complex osseous structures.