Patchy increased echogenicity: a sonographic sign of femoral head necrosis following reduction and casting for developmental dysplasia of the hip.

A developmental dysplasia of the hip (DDH) case treated by closed reduction and casting and subsequently confirmed to have avascular necrosis (AVN) was retrospectively noted to have an abnormal pattern of echogenicity in the femoral head on sonograms obtained within 1.5 months of surgery. Patchy increased echogenicity in parts of the unossified cartilage replaced the normal pattern of central coalescence of vessels described with development of the ossification center. An additional case with similar findings confirms this should be considered a sign of evolving AVN following closed reduction.