Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are slightly low . Aside from minimal bibasilar atelectasis , the lungs are clear . The heart is moderately enlarged . The mediastinal contours are normal . There are no definite pleural effusions . No pneumothorax . The patient is status post midline sternotomy and CABG . Marked degenerative changes of the right acromioclavicular joint are seen . A cortical step - off in the anterolateral aspect of the right sixth rib is consistent with a minimally displaced fracture . No definite additional rib fractures are seen .
    OUTPUT:
    
1 . Minimally displaced right sixth rib fracture . No definite additional rib fractures are identified , although a dedicated rib series with appropriately placed skin markers could provide further evaluation if clinically indicated . 2 . No evidence of pneumothorax . 3 . Moderate cardiomegaly .