Caitlin M. Locey

Protection of children restrained in child safety seats in side impact crashes.

BACKGROUND The performance of child restraint systems (CRS) in side impact motor vehicle crashes has been under study due to the injury and fatality burden of these events. Although previous research has quantified injury risk or described injured body regions, safety advances require an understanding of injury causation. Therefore, the objective was to delineate injury causation scenarios for CRS-restrained children in side impacts and document probable contact points in the vehicle interior. METHODS Two in-depth crash investigation databases, the Crash Injury Research and Engineering Network and the Partners for Child Passenger Safety Study, were queried for rear-seated, CRS-restrained children in side impact crashes who sustained Abbreviated Injury Scale 2+ injury. These cases were reviewed by a multidisciplinary team of physicians and engineers to describe injury patterns, injury causation, and vehicle components that contributed to the injuries. RESULTS Forty-one occupants (average age, 2.6 years) met the inclusion criteria. Twenty-four were near side to the crash, 7 were far side, and 10 were center seated. The most common injuries were to the skull and brain with an increasing proportion of skull fracture as age increased. Head and spine injuries without evidence of head contact were rare but present. All thoracic injuries were lung contusions and no rib fractures occurred. Near-side head and face contacts points were along the rear vertical plane of the window and the horizontal plane of the window sill. Head and face contact points for center- and far-side occupants were along the edges of the front seat back and front seat head restraint. CONCLUSIONS Head injuries are the target for injury prevention for children in CRS in side impact crashes. Most of these injuries are due to the contact; for near-side occupants, contact with the CRS structure and the door interior, for far- or center-seated occupants, contact with the front seat back. These data are useful in developing both educational and technological interventions to reduce the burden of injury to these children.

Head impact contact points for restrained child occupants.

Objective: Head injuries are the most common injuries sustained by children in motor vehicle crashes regardless of age, restraint, and crash direction. For rear seat occupants, the interaction of the subject with the seat back and the vehicle side interior structures has been previously highlighted. In order to advance this knowledge to the development of countermeasures, a summary of vehicle components that contributed to these injuries is needed. Therefore, the objective of this study was to create a contact map of the vehicle interior for head and face injuries to rear-seated restrained children in front crashes. Methods: The Crash Injury Research and Engineering Network (CIREN) was queried for rear-seated, restrained child occupants (age 0–15 years) in forward-facing child restraints, booster seats, or lap and shoulder belts who sustained an AIS2+ head and/or face injury in a frontal motor vehicle crash. Cases were analyzed to describe injury patterns and injury causation scenarios. A contact point map was developed to summarize the vehicle components related to injury causation of the head/face injury. Results: Twenty-one cases met the combined inclusion and exclusion criteria. Seven of the child occupants were restrained in forward-facing child restraints, 2 in belt-positioning booster seats, and 12 in lap and shoulder belts. There were 28 head and 17 facial injuries. For left rear occupants, the most common contact point was the pillar in front of the occupants seat row; that is, B-pillar for second-row occupants, indicating a leftward kinematics. For right rear occupants, due to differences in crash dynamics, the most common contact point location was the passengers seat back, suggesting that these occupants moved predominantly forward. Conclusions: Contact points associated with head/face injury for restrained children 0 to 15 years in frontal crashes have been delineated. In a majority of the cases, the head/face injury was the most severe injury and severe injuries to other body regions were uncommon, suggesting that efforts to mitigate head injuries for these occupants would greatly improve their overall safety. The majority of the head/face contact points were to the first row seat back and B-pillar. In these frontal crashes, the importance of head/face contact with the vehicle side structure suggests that deploying a curtain air bag in frontal impacts may help manage the energy of impact. These data advance the current understanding of injury patterns and causation in frontal crashes involving restrained rear-row occupants and can be used to develop solutions to mitigate the injuries sustained.

Lower extremity injuries in children seated in forward facing child restraint systems.

Objective. The lower extremity is among the most frequently injured body regions for children restrained by forward facing child restraint systems (FFCRS), accounting for 28% of their clinically significant injuries, defined as AIS 2 and greater injuries excluding concussions. Despite the prevalence of these injuries, the current U.S. Motor Vehicle Safety Standard governing FFCRS (FMVSS 213) does not provide a direct assessment of the biomechanical risk of lower extremity fracture nor do the current pediatric test devices provide adequate instrumentation to detect the risk of such injuries. Before improvements can be made to the anthropometric test devices (ATDs) or test procedures to address these limitations, understanding of the sources and mechanisms of these injuries is necessary. Therefore, the objective of this study was to document location, source, and crash circumstances of lower extremity injuries in children seated in FFCRS. Methods. Utilizing two sources of data, PCPS and CIREN, 20 in-depth investigations of crashes involving children seated in FFCRS with lower extremity injuries were reviewed to determine the nature of the injuries and the circumstances under which they occurred. Results. Injuries below the knee were the most common, particularly to the tibia/fibula, and they most often occurred due to interaction with the vehicle seatback in front of the childs seating position. These injuries were sustained most commonly in frontal impacts although interaction with the seatback also occurred in other crash types. This interaction with the seatback was exacerbated by possible contributing factors such as intrusion of the front seatback into the childs occupant space or FFCRS misuse resulting in increased excursion of the child during impact. Conclusions. This review of cases of children in FFCRS with AIS 2 and greater lower extremity injury points to the role of the seatback in the occurrence of these injuries, suggesting the need to consider this interaction in the seatback design process and to adequately represent this interaction in regulatory procedures assessing the performance of child restraints.

Evaluation of pediatric ATD biofidelity as compared to child volunteers in low-speed far-side oblique and lateral impacts.

Objective: Motor vehicle crashes are a leading cause of injury and mortality for children. Mitigation of these injuries requires biofidelic anthropomorphic test devices (ATDs) to design and evaluate automotive safety systems. Effective countermeasures exist for frontal and near-side impacts but are limited for far-side impacts. Consequently, far-side impacts represent increased injury and mortality rates compared to frontal impacts. Thus, the objective of this study was to evaluate the biofidelity of the Hybrid III and Q-series pediatric ATDs in low-speed far-side impacts, with and without shoulder belt pretightening. Methods: Low-speed (2 g) far-side oblique (60°) and lateral (90°) sled tests were conducted using the Hybrid III and Q-series 6- and 10-year-old ATDs. ATDs were restrained by a lap and shoulder belt equipped with a precrash belt pretightener. Photoreflective targets were attached to the head, spine, shoulders, and sternum. ATDs were exposed to 8 low-speed sled tests: 2 oblique nontightened, 2 oblique pretightened, 2 lateral nontightened, 2 lateral pretightened. ATDs were compared with previously collected 9- to 11-year-old (n = 10) volunteer data and newly collected 6- to 8-year-old volunteer data (n = 7) tested with similar methods. Kinematic data were collected from a 3D target tracking system. Metrics of comparison included excursion, seat belt and seat pan reaction loads, belt-to-torso angle, and shoulder belt slip-out. Results: The ATDs exhibited increased lateral excursion of the head top, C4, and T1 as well as increased downward excursion of the head top compared to the volunteers. Volunteers exhibited greater forward excursion than the ATDs in oblique nontightened impacts. These kinematics correspond to increased shoulder belt slip-out for the ATDs in oblique tests (ATDs = 90%; volunteers = 36%). Contrarily, similar shoulder belt slip-out was observed between ATDs and volunteers in lateral impacts (ATDs = 80%; volunteers = 78%). In pretightened impacts, the ATDs exhibited reduced lateral excursion and torso roll-out angle compared to the volunteers. Conclusions: In general, the ATDs overestimated lateral excursion in both impact directions, while underestimating forward excursion of the head and neck in oblique impacts compared to the pediatric volunteers. This was primarily due to pendulum-like lateral bending of the entire ATD torso compared to translation of the thorax relative to the abdomen prior to the lateral bending of the upper torso in the volunteers, likely due to the multisegmented spinal column in the volunteers. Additionally, the effect of belt pretightening on occupant kinematics was greater for the ATDs than the volunteers.

Comparative Performance of Forward-Facing Child Restraint Systems on the C/FMVSS 213 Bench and Vehicle Seats

Objective: The objective of this study was to evaluate the fidelity of the C/FMVSS 213 test bench, by comparing the dynamic performance of forward-facing child restraint systems (FFCRS) mounted on the C/FMVSS 213 sled bench versus mounted on a selection of production vehicle seats. Methods: The C/FMVSS 213 bench or one of 3 second-row original equipment manufacturer vehicle seats was mounted to the deck of acceleration crash sled. An FFCRS with a restrained anthropomorphic test device (ATD) was secured by 3-point belt (3-PT) or LATCH lower anchor (LLA) on the C/FMVSS 213 bench or vehicle seat, with or without a tether. The sled was then exposed to a 48 km/h acceleration pulse. Three unique make and model vehicle seats and FFCRS were tested. Fifty-three sled tests were performed. Results: When FFCRS were secured with LLA and no tether, little difference between the vehicle seats and 213 bench was observed. Similarly, when FFCRS were affixed with 3-PT and no tether, few kinematic variable differences achieved statistical significance; chest resultant acceleration was, on average, 9.1 g (SD = 6.6, P =.006) higher on the vehicle seats compared to the bench, as was CRS seatback excursion (difference [Δ] of 39.8 mm, SD = 32.7, P =.011) and ATD knee excursion (Δ = 36.4 mm, SD = 12.0, P < .001). However, when the tether was added to either the 3-PT or LLA attachment methods, the difference between the bench and vehicle seats was more pronounced. ATD kinematic measures such as head resultant acceleration (Δ = 14.6 g, SD = 7.2, P <.001) and pelvis resultant acceleration (Δ = 8.6 g, SD = 6.0, P =.005) were higher on the vehicle seats compared to the bench, as were the injury metrics for head and chest injury: ΔHIC15 = 162.2 (SD = 87.4, P =.001) and ΔChest 3 ms clip = 5.5 g (SD = 6.2, P =.040). Of note, CRS (Δ = 62.8 mm, SD = 32.7, P =.000) and ATD head (Δ = 66.3 mm, SD = 30.9, P =.000) and knee (Δ = 46.9 mm, SD = 25.8, P =.001) forward excursion were all higher on the vehicle seats compared to the bench in 3-PT with tether condition. Conclusions: Without the tether attached, we observed few kinematic and kinetic differences between the vehicle seat and the C/FMVSS 213 bench, suggesting that the bench is an adequate surrogate for the vehicle seat in this condition. With the tether attached, we found significant differences between the C/FMVSS 213 bench and vehicle seats, suggesting that the fidelity of the bench could be improved in the tethered mode. When differences were statistically significant, excursion and injury metrics were generally greater on the vehicle seats than on the C/FMVSS 213 bench.

Pediatric occupant-vehicle contact maps in rollover motor vehicle crashes

Objective: Rollover crashes account for more than 33% of all motor vehicle–related fatalities and have the highest fatality risk of all crash types, at 1.37% in the United States. There is increased awareness of the high fatality rate associated with this crash type, but there is very limited pediatric-specific data related to rollover crashes in the United States. Recent focus on rollover mitigation has resulted in implementation of countermeasures, making it important to evaluate injury causation for child occupants in rollover crashes with a more current data set. Methods: We queried the Crash Injury Research and Engineering Network (CIREN) from case years 1998 through 2013. Rollover crashes for passenger vehicles of model year 1998 or newer with at least one restrained occupant (excluding drivers) between 0 and 19 years of age were included. Vehicle-involved physical component and occupant–vehicle contact maps were developed with the CIREN data set. Results and Conclusions: Of the 20 CIREN cases that met the inclusion criteria, 15 had one or more injuries attributed to contact with some part of the vehicle structure. The CIREN analyses revealed that the head was the most common seriously injured body region, primarily due to contact with the roof side rail and/or vehicle interior. This finding was true for both adolescents and younger pediatric passengers in outboard seating positions. Fifty percent of head injury causation scenarios involving the vehicle interior had component intrusion of 20+ cm at the point of contact. Further exploration of pediatric rollover injury mechanisms using computational modeling and real-world testing is recommended in order to improve upon current mitigation strategies.

Motor Vehicle Crash–Related Injury Causation Scenarios for Spinal Injuries in Restrained Children and Adolescents

Objective: Motor vehicle crash (MVC)-related spinal injuries result in significant morbidity and mortality in children. The objective was to identify MVC-related injury causation scenarios for spinal injuries in restrained children. Methods: This was a case series of occupants in MVCs from the Crash Injury Research and Engineering Network (CIREN) data set. Occupants aged 0–17 years old with at least one Abbreviated Injury Scale (AIS) 2+ severity spinal injury in vehicles model year 1990+ that did not experience a rollover were included. Unrestrained occupants, those not using the shoulder portion of the belt restraint, and those with child restraint gross misuse were excluded. Occupants with preexisting comorbidities contributing to spinal injury and occupants with limited injury information were also excluded. A multidisciplinary team retrospectively reviewed each case to determine injury causation scenarios (ICSs). Crash conditions, occupant and restraint characteristics, and injuries were qualitatively summarized. Results: Fifty-nine cases met the study inclusion criteria and 17 were excluded. The 42 occupants included sustained 97 distinct AIS 2+ spinal injuries (27 cervical, 22 thoracic, and 48 lumbar; 80 AIS-2, 15 AIS-3, 1 AIS-5, and 1 AIS-6), with fracture as the most common injury type (80%). Spinal-injured occupants were most frequently in passenger cars (64%), and crash direction was most often frontal (62%). Mean delta-V was 51.3 km/h ± 19.4 km/h. The average occupant age was 12.4 ± 5.3 years old, and 48% were 16- to 17-year-olds. Thirty-six percent were right front passengers and 26% were drivers. Most occupants were lap and shoulder belt restrained (88%). Non-spinal AIS 2+ injuries included those of the lower extremity and pelvis (n = 56), head (n = 43), abdomen (n = 39), and thorax (n = 36). Spinal injury causation was typically due to flexion or lateral bending over the lap and or shoulder belt or child restraint harness, compression by occupants own seat back, or axial loading through the seat pan. Nearly all injuries in children <12 years occurred by flexion over a restraint, whereas teenage passengers had flexion, direct contact, and other ICS mechanisms. All of the occupants with frontal flexion mechanism had injuries to the lumbar spine, and most (78%) had associated hollow or solid organ abdominal injuries. Conclusions: Restrained children in nonrollover MVCs with spinal injuries in the CIREN database are most frequently in high-speed frontal crashes, of teenage age, and have vertebral fractures. There are age-specific mechanism patterns that should be further explored. Because even moderate spinal trauma can result in measurable morbidity, future efforts should focus on mitigating these injuries.

Headform impact tests to assess energy management of seat back contact points associated with head injury for pediatric occupants

Head injuries are the most common injuries sustained by children in motor vehicle crashes regardless of age, restraint and crash direction. Previous research identified the front seat back as relevant contact point associated with head injuries sustained by restrained rear seated child occupants. The objective of this study was to conduct a test series of headform impacts to seat backs to evaluate the energy management characteristics of relevant contact points for pediatric head injury. A total of eight seats were tested: two each of 2007 Ford Focus, Toyota Corolla, 2006 Volvo S40, and 2008 Volkswagen Golf. Five to six contact points were chosen for each unique seat model guided by contact locations determined from real world crashes. Each vehicle seat was rigidly mounted in the center track position with the seatback angle adjusted to 70 degrees above the horizontal. A 3.5 kg child pedestrian headform was fired at a velocity of 24 km/h (6.67 m/s) in accordance to FMVSS 201 at 22 degrees above the horizontal starting from 10 cm from the center of the target. Resultant acceleration and HIC (15 ms and 36 ms) were calculated for each impact. Within the class of small family vehicles, there was substantial variation in underlying seat structure across the locations of head impact identified in the case series resulting in a wide range of maximum resultant head acceleration - 27-165 g. Several impact locations, particularly those around the edge of seat back resulted in head acceleration greater than 80g used in regulatory tests. These data highlight the need to re-examine the current FMVSS 201, Occupant Protection in Interior Impact, to account for the typical impact locations of child occupants in crashes. In addition, further study is needed to understand the tolerance of the pediatric skull and brain to these types of impacts. Language: en