Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiac silhouette size is normal . The aorta is mildly tortuous but unchanged . The pulmonary vascularity is normal . Lungs are clear . No pleural effusion or pneumothorax is identified . There are mild degenerative changes in the thoracic spine . Fracture of the left seventh posterior rib is minimally displaced .
    OUTPUT:
    
Mildly displaced left seventh posterior rib fracture . No pleural effusion or pneumothorax .