Bilateral carotid artery injury response in side impact using a vessel model integrated with a human body model

In a far-side crash configuration, the occupant can experience severe excursion from the seat space. Given this challenge, there are research efforts focused on alternate restraints, such as four-point belts. A potential implication of this geometry would be interaction of the belt with the occupant's neck. This study examines the response of the carotid arteries using a Finite Element Model (FEM) in a far-side crash configuration with a reversed three-point restraint. A FEM of the carotid artery and neck fascia was developed and integrated with the Total Human Model for Safety (THUMS) version 1.44. This model was subjected to four test conditions simulating far-side crashes. Load conditions included a low velocity impact of approximately 4 m/s and a higher velocity impact of approximately 10 m/s. For each velocity, the model was restrained with a belt placed low on the neck and a belt placed higher on the neck. Strain data in each element of the carotid arteries was analyzed. The overall response of the vessel was examined to determine locations of high strain values. Low belt placement resulted in more head excursion, stretching the carotid on the non-struck side. High belt placement resulted in compression of the artery on the struck side due to direct loading of the vessel from the belt. Strain values in the carotid artery elements increased with increasing speed of impact. The lower and higher speed tests with a low belt configuration resulted in a maximum principal strains, at maximal belt engagement, of 0.223 and 0.459, respectively. Corresponding values for the high belt configuration were 0.222 and 0.563. In both belt configurations, the non-struck side vessel stretched more than the struck side vessel; however, the non-struck side vessel experienced higher compressive forces. Strain values measured during the simulations can be compared to a value of 0.31 to intimal failure in previous experimental tests. These results quantitatively illustrate the two primary mechanisms of injury to the carotid artery: tension and intima-to-intima contact of the vessel. Based on the study, low belt placement and limiting head excursion is recommended to reduce both stretching and compression of the carotids in side impact.