rib cage vs thoracic cage

rib cage

noun
  • The enclosed area created by and within the ribs. 

  • A part of the skeleton within the thoracic area consisting of ribs, sternum and thoracic vertebrae. 

thoracic cage

noun
  • A rib cage. 

How often have the words rib cage and thoracic cage occurred in a corpus of books? (source: Google Ngram Viewer )