Sensitivity of Porcine Thoracic Responses and Injuries to Various Frontal and A Lateral Impact Site 780890

Classical blunt thoracic impacts have involved midsternal anteroposterior loadings to an upright-positioned subject. Data on the sensitivity of human cadaver and/or animal model biomechanical and injury responses to blunt loadings at different sternal locations is needed to evaluate the efficacy of current injury-potential guidelines for nonsite-specific frontal impacts. In addition, the biomechanics and injury mechanisms associated with lateral impacts constitute a subject of increasing consideration for occupant protection.

Twelve anesthetized pigs were subjected to various blunt frontal or a right-side impact to assess biomechanical and injury response differences in a living animal model. For frontal impacts, thoracic compliance (i.e., sternal acceleration, normalized deflection, blood over-pressure, as well as force-deflection characteristics) and injury (i.e., skeletal and visceral trauma, and conduction dysfunction) were significantly affected by the location of the sternal load. Impacts above midsternum (to a relatively stiff thorax) produced infrequent skeletal damage but serious mediastinal hemorrhaging and lung laceration; whereas, impacts below midsternum (to a more compliant thorax) resulted in extensive skeletal damage and liver laceration. For lateral impacts, large penetration into the rib cage produced serious liver injuries with extensive near-side skeletal damage in one case and no fractures in the other.

The evaluation of functional response to impact was enhanced by analysis of potential heart dysfunctions and of variations in blood catecholamines. Disturbances of the myocardial conducting system were observed from multi-lead ECG recordings. Left anterior hemiblock was frequently observed after impacts at or below midsternum. The block either resolved or progressed to ventricular fibrillation in several minutes. In an analysis of the induced stress, a transient increase was observed in plasma catecholamine concentrations which was rapidly alleviated within minutes after the impact.