Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart is normal in size . There is slight unfolding and calcification along the thoracic aorta . The mediastinal and hilar contours appear within normal limits . The lungs appear clear . There is no pleural effusion or pneumothorax . There are nondisplaced posterolateral fractures involving the left sixth and seventh ribs , of uncertain acuity .
    OUTPUT:
    
Rib fractures , without displacement , but of uncertain acuity . No evidence of acute cardiopulmonary disease .