The radiographic recognition of sternal retraction in infants.

Sternal retraction is a common clinical sign of respiratory distress in premature infants. Frontal chest radiographs show increased, ill-defined central radiolucency over the lower chest which correlates well with a curvilinear indentation seen on lateral views. Misinterpretation as technical artefact or confusion with pneumomediastinum, pneumothorax or pneumopericardium should be avoided. Cardiac displacement in severe cases may stimulate cardiomegaly. Sternal retraction happens because of the poor expansion of non-compliant lungs and a relatively soft anterior chest wall which caves in under increased negative intrathoracic pressure. Illustrative cases are shown and discussed.