title: Mechanical factors associated with posterior rib fractures: laboratory and case studies.
abstract: OBJECTIVE
  The objective of this study was to explore the mechanical factors associated with posterior rib fractures.
  
  
  METHODS
  Radiographs were reviewed in ten cadavers where rib fractures were produced by opening a median sternotomy with a sternal retractor. A second study used CT to evaluate for rib fractures following digital sternal depression and anteroposterior bimanual thoracic compression in three rabbits. Lastly, two cases of accidental posterior rib fractures in children were reviewed.
  
  
  RESULTS
  In the cadaver studies, ten rib fractures were noted, all at or medial to the costotransverse process articulations. In the rabbit study, 13 posterior rib fractures were noted, all occurring with excessive posterior levering of the ribs during bimanual compression. The accidental posterior rib fractures occurred with severe anteroposterior thoracic compression as children were decelerated into a car dashboard or struck by a car.
  
  
  CONCLUSIONS
  Posterior rib fractures require excessive levering of the posterior ribs at the costotransverse process articulation. When these fractures occur in accidental situations, they require massive forces that entail similar mechanics to those occurring in abusive settings.
authors.affiliation: Department of Radiology, Imaging Center for Child Abuse and Neglect, University of Massachusetts Medical Center, 55 Lake Avenue North, Worcester, MA 01655, USA.
authors.forename: P K
authors.initials: PK
authors.lastname: Kleinman
authors.forename: A E
authors.initials: AE
authors.lastname: Schlesinger
mesh_terms: D000063:Accidents, Traffic; D000818:Animals; D001696:Biomechanical Phenomena; D002649:Child Abuse / Q000175:diagnosis*; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D008297:Male; D011817:Rabbits; D011859:Radiography; D012253:Rib Fractures / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology