Factors associated with chest injuries to front seat occupants in frontal impacts

Objective: Improving crash protection for older car occupants is a matter of urgency since the number of older car users is forecast to grow dramatically over the next two decades. The thorax is particularly vulnerable in older occupants, and this study aimed to provide real-world in-depth analysis of factors contributing to chest injuries in frontal impacts involving European cars. Methods: Real world crash injury data were interrogated, focusing on cars with current restraint components. The research examined belted front-seat occupants in frontal impacts where air bags, pretensioners and load limiters were present. Results: The chest was the most often injured body region at AIS 2+, 3+ and 4+ injury levels. The rate of AIS 2+ and AIS 3+ chest injuries was highest among elderly occupants and lowest among young occupants, and elderly occupants sustained proportionally more severe chest injuries in low/moderate speed impacts compared to young and middle-aged occupants. However, it should be noted that rates of AIS 2 chest injury were also significantly higher for middle-aged occupants compared to the young. The front passenger seat was shown to be more often associated with significant chest injury than the driver seat. The higher proportion of elderly female occupants was postulated as a reason for this. Skeletal injury was the most frequent type of AIS 2+ chest injury and the rate of injury for elderly occupants with such injuries was higher than for young and middle-aged occupants. With the increase in the number of rib fractures, the risk of pulmonary complications and organ injuries tended to increase. The major cause of chest injury was identified as restraining loads transmitted to the chest via the seat belt. The absence of intrusion in the majority of cases, suggests an opportunity for the restraint system to better manage the crash pulse. Not only for elderly occupants but for those who are middle-aged as well. Conclusions: This study shows the necessity for safety interventions, through new vehicle crashworthiness systems to improve chest protection especially for middle aged and elderly car occupants. Deployment of appropriate injury risk criteria, use of an appropriate dummy thorax, development of a low energy restraint test, and the development of more adaptive restraints have been discussed as possible solutions to the problem.