Mechanical factors associated with posterior rib fractures: laboratory and case studies

Objective. The objective of this study was to explore the mechanical factors associated with posterior rib fractures. Materials and 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. Conclusion. 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.