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Head Injury Causation Scenarios for Belted, Rear-Seated Children in Frontal Impacts

Objectives: Head injuries are the most common serious injuries sustained by children in motor vehicle crashes and are of critical importance with regard to long-term disability. There is a lack of understanding of how seat belt–restrained children sustain head injuries in frontal impacts. The aim of the study was to identify the AIS2+ head injury causation scenarios for rear-seated, belt-restrained children in frontal impacts, including the set of parameters contributing to the injury. Method: In-depth crash investigations from two National Highway Traffic Safety Administration (NHTSA) databases, the National Automotive Sampling System–Crashworthiness Data System (NASS-CDS; 1997–2008) and the Crash Injury Research and Engineering Network (CIREN; 1996–2009), were collected and analyzed in detail. Selection criteria were all frontal impacts with principal direction of force (PDOF) of 11, 12, and 1 o’clock involving rear-seated, three-point belt-restrained, with or without booster cushion, children from 3 to 13 years with an AIS2+ head injury. Cases were analyzed using the BioTab method of injury causation assessment in order to systematically analyze the injury causation scenario for each case. Results: There were 27 cases meeting the inclusion criteria, 19 cases with MAIS2 head injuries and 8 cases with MAIS3+ head injuries, including 2 fatalities. Three major injury causation scenarios were identified, including head contact with seatback (10 cases), head contact with side interior (7 cases,) and no evidence of head contact (9 cases). Conclusions: Head injuries with seatback or side interior contact typically included a PDOF greater than 10 degree (similar to the Insurance Institute for Highway Safety [IIHS] and EuroNCAP offset frontal testing) and vehicle maneuvers. For seatback contact, the vehicle's movements contributed to occupant kinematics inboard the vehicle, causing a less than optimal restraint of the torso and/or torso roll out of the shoulder belt. For side interior contact, the PDOF and/or maneuvers forced the occupant toward the side interior. The cases without evidence of head/face contact were characterized by high crash severity and accompanied by severe injuries to the thorax and spine. These data lead to increased understanding of the injury patterns and causation in this crash restraint scenario so that interventions to mitigate the burden of injury can be advanced.