Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are underinflated but clear . Cardiomediastinal silhouette is normal . There is no pleural effusion or pneumothorax . No displaced rib fractures are identified . On the lateral view , there is suggestion of subtle cortical step - off at the posterior aspect of the sternum , which may represent a fracture .
    OUTPUT:
    
Subtle cortical step - off at the posterior aspect of the sternum , could represent a sternal fracture vs artifact . Correlate clinically with anterior chest pain and history .