Dynamics of Frontal Collisions between Vehicles and Associated Trauma: A Literature Review

I. INTRODUCTION

Traffic accident-related traumas are the leading cause of mortality among adolescents and young adults aged 15 to 29 years. Moreover, they represent a significant financial burden on public finances, with estimated costs of approximately 3% of the annual GDP, impacting sectors such as healthcare, infrastructure, and productivity [1]. In developed countries, such as the United States, traffic accidents began to be recognized as a serious problem throughout the 20th century due to the rapid increase in the number of automobiles. In developing countries, such as Brazil, the social significance of this issue emerged in the 1970s, partly due to the growing reliance on motor vehicles for urban mobility and goods transportation, exacerbated by the lack of alternatives such as railway transportation [2].

A car accident encompasses multiple factors, such as human error, vehicle conditions, and the physical and social environment surrounding the incident $[3]$. The human factor is the most significant, responsible for up to 90% of traffic accidents. In this regard, one of the aspects studied is the driver's behavior while driving, particularly overconfidence and engaging in activities during driving that may distract them and significantly impair their ability to operate a vehicle $[4]$, such as reaching for objects, adjusting the radio, eating, drinking, and using electronic devices like cell phones, GPS, and tablets, among others. Engaging in these activities causes the driver to divert their attention, impairing their ability to react promptly and avoid a collision $[5]$.

Still within this context, accidents commonly result in polytrauma, and several criteria have been established to assess injury severity in frontal collisions. Among the parameters used to evaluate vehicle occupant responses to impact are acceleration, force, and torque, which are applied in biomechanical studies $[6]$. Different criteria have been proposed for various body regions to assess the severity of injuries in car accidents, such as the head injury criterion, which is based on the acceleration of the head during the collision $[7]$.

In this context, given the growing importance of the topic, this article aims to conduct a literature review to identify and analyze the main patterns of injuries in frontal vehicle collisions. Through the analysis of recent studies and data from various research efforts, the goal is to understand the characteristics and severity of the most common injuries in these situations, as well as to evaluate factors contributing to the intensity of impact and the human body's response.

II. METHODOLOGY

This is a literature review conducted between November and December 2024, utilizing the MEDLINE database. The search used the keyword "frontal car crashes" and was restricted to studies published within the last five years. The initial search yielded 102 articles. After screening, which used the following inclusion criteria: studies that reported only the outcomes of frontal collisions between vehicles, whether involving similar models or real-case scenarios, literature review studies were excluded. A total of 8 articles were selected.

The stages of this research were organized as follows: first, the appropriate descriptors were determined; then, in a sequential manner, the search strategy was developed, the databases were selected, the most relevant titles were chosen, and a complete reading of the texts was performed. Finally, these steps culminated in the preparation of the text.

Due to the use of secondary data from public domain sources, it was not necessary to submit the project to a Research Ethics Committee.

III. RESULTS

Table 1 presents the research results, organizing the studies according to the year of publication and their objectives. This structure was chosen for its ability to provide a comparative overview of the selected studies.

IV. DISCUSSION

Injuries resulting from the mechanism of frontal collisions in automobile accidents are associated with high rates of morbidity and mortality in the adult population. The main injuries from these collisions occur due to the interaction of the victim with the automobile. Facial, aortic, and extremity injuries are the most commonly reported in frontal vehicle collisions. Trauma related to the steering wheel is directly linked to thoracic structures, such as rib fractures, sternum fractures, myocardial contusion, aortic injuries, and pulmonary injuries. The lower extremities are directly impacted by forces opposing the victim's ejection, resulting from the interaction of the pelvis and lower limbs with the vehicle's dashboard [8].

The epidemiological analysis conducted by Ranmal et al [9] collected weighted German data from 1999 to 2021, evaluating risk curves to predict rib and sternum fractures in frontal automobile collisions. The review revealed that elderly individuals and women have a significantly higher risk of thoracic injuries in accidents with this collision mechanism. Rib and sternum fractures were more commonly associated with the population over 65 years old compared to individuals aged 18-64 years. The data showed that women have a higher risk of sustaining more severe rib injuries and isolated sternum injuries compared to men.

Khojastepour et al [10] assessed the prevalence of frontal sinus injuries in 91 trauma patients treated at Rajaee Hospital in Shiraz between 2014 and 2019. The analysis revealed a higher prevalence of these injuries among victims of automobile accidents caused by frontal collision mechanisms. Frontal sinus injuries occurred frequently (74.7%) in conjunction with other facial injuries. Furthermore, combined fractures of the anterior and posterior table were more commonly observed than isolated involvement of either table.

Both Ranmal and Khojastepour [9,10] demonstrated that there is a pattern of injuries associated with facial and thoracic injuries that correlate with the mechanism involved in automobile accidents. A frontal collision promotes the projection of the individual against the vehicle's structure, significantly impacting facial and thoracic regions. The injuries are varied and exhibit a wide spectrum of severity, ranging from fatal to those with a good prognosis without the need for immediate medical intervention [8].

Ellahi et al [11] evaluated patterns of injuries in frontal vehicle crash tests against fixed barriers, aiming to analyze trauma patterns in biofidelic human body models. The study quantified the pressure required for structural injury occurrence. The megapascal (MPa) is a unit of pressure measurement in the International System of Units (SI) that represents force applied per unit area, equivalent to 1 million pascals (Pa). A pascal is defined as 1 newton per square meter (N/m2). Rib fractures (5-7) were observed at stresses of 120 MPa in the left lateral vertebrosternal region. In the lower extremity, ligament ruptures were identified at 70.80 MPa, while fractures in the tibia and femur occurred at 236 MPa. Cranial stresses were limited to 11 MPa, suggesting the possibility of concussions rather than fractures. Therefore, traumatic injuries highlight a significant relationship between the individual and the vehicle, with the main complications arising from impacts causing considerable deceleration of the vehicle-victim system [12].

Tang et al. [13] demonstrated through simulations that the incidence of submersion in victims of frontal collisions is reduced in newer vehicles. However, they observed a higher risk of lumbar spine fractures associated with these collisions. The findings indicated that factors reducing the risk of submersion simultaneously increased the forces affecting the victim's lumbar spine. From a biomechanical perspective, the primary mechanism of lumbar spine fracture is high-energy axial compression, with or without flexion transferred to the region [14, 15, 16, 17, 18, 19]. The vehicle's angle of inclination was identified as the most influential parameter in determining the lumbar spine injury pattern, with increased angulation raising the risk of fractures. On average, an erect posture applies less force to the lumbar spine compared to a reclined posture, resulting in a reduced risk of lumbar fractures in frontal vehicle collisions [13]

Joodaki et al. [20], in a retrospective cohort study, analyzed 13,470 frontal collision cases from the US National Automotive Sampling System-Crashworthiness Data System. The aim was to evaluate the influence of body mass index (BMI) on injury risks across different body regions. Results revealed an increased incidence of injuries in obese individuals compared to non-obese individuals: 4.79% versus 2.92% in the upper extremities; 8.37% versus 3.23% in the lower extremities; and 1.53% versus 1.09% in the spinal column. Among lower extremity injuries, talus fractures were the most common. These differences in injury patterns are linked to the interaction between overweight individuals, seatbelt use, and the vehicle's interior, which affect the forces during collision impacts.

Kuwahara et al. [21] observed that non-pregnant women sustained more moderate to severe injuries, with higher scores on the AIS scale, particularly in head injuries, compared to pregnant women. No evidence was found indicating an increased risk of abdominal injuries in pregnant women, regardless of abdominal protrusion or gestational week. Other non-pregnancy-related factors appeared to be more closely associated with abdominal injuries, showing similar numbers between pregnant and non-pregnant women. Regarding fetal risk, fetal harm was more closely linked to the severity of the maternal abdominal injury, with more severe cases being more detrimental to the fetus.

Additionally, changing the pregnant woman's seat position did not demonstrate any significant impact on the risk to the maternal-fetal dyad during frontal automobile collisions.

Jermakian et al. [22], analyzing data from the National Automotive Sampling System Crashworthiness Data System (NASS-CDS, 2004-2015) and the Fatality Analysis Reporting System (FARS, 2014-2015), demonstrated greater severity of injuries among rear-seat occupants involved in automobile crashes compared to front-seat occupants. In frontal collisions, after adjusting for variables such as occupant age, impact direction, and other factors, no increased risk of death was identified for rear-seat occupants compared to those in the front seat. However, frontal impacts were responsible for a higher proportion (34%) of fatalities among rear-seat occupants who were restrained.

The affected body regions varied according to the lethality of the event and the victims' age (Figure 1). Among survivors, thoracic injuries were the most prevalent, followed by facial and head injuries, regardless of age. In fatal cases, differences in injury patterns were observed based on age groups. For victims over 55 years old, thoracic injuries were the most common. In contrast, among children aged 6 to 12 years, head and facial injuries were more frequent [22].

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Jermakian et al. also investigated collision and restraint factors related to injuries and deaths among rear seat occupants during frontal impacts in newer vehicle models. The primary factors responsible for injuries included seatbelt loading and impact with the vehicle's interior. In fatal cases, the most relevant factors were seatbelt loading and the severity of the collision, considered unsurvivable. Chest compression caused by the seat belt resulted in different injury patterns depending on the victim's biophysical profile and age. Children experienced a higher incidence of blunt pulmonary injuries, while adults showed a greater frequency of rib fractures, cardiac injuries, and vascular injuries (Table 2).

The prevalence of traumatic injuries in frontal collisions is heterogeneous and influenced by various factors, particularly the interaction between the individual and the automobile.

Among the variables related to the victims, body mass index (BMI), seating position in the vehicle, and the collision's intensity are the most significant factors described in the literature [Concerning the automobile, the restraining force of the seatbelt and the impact with the vehicle's interior represent the primary interactions during the collision event [22].

V. CONCLUSIONS

The analysis of the 8 selected articles provided relevant information regarding the patterns of trauma in victims of automobile accidents with frontal collision mechanisms, offering insight into the factors influencing the severity of injuries in these accidents.

The analyzed data demonstrate that the patterns of trauma in frontal collisions exhibit wide variability and are influenced by multiple factors related both to the individual characteristics of the victim and the characteristics of the vehicle. Variables such as BMI, position in the vehicle, and the collision's intensity have a direct relationship with the likelihood of injury occurrence and the severity of the trauma. Furthermore, vehicle-related factors, such as the restraining force of the seatbelt and impact with the interior of the vehicle, play a determining role in the dynamics and severity of injuries, as evidenced by the studies analyzed in the literature review and compared with current medical literature $[13,20,22]$. These findings underscore the importance of addressing the biomechanics of injuries from a multidimensional perspective to better understand the complexity of trauma in collisions.

The findings also indicate differentiated patterns of injuries in children and adults, highlighting the importance of the biophysical profile during impact. These differences reflect not only physical characteristics but also the specific mechanisms of impact dynamics and individual biomechanical responses. Therefore, analyzing these patterns should be considered in prevention strategies and the development of safety devices tailored to different age groups.

Furthermore, the data suggest that the prevention of injuries in frontal collisions should involve both vehicle adaptation and awareness of individual risk factors. Strategies such as improving restraint systems, adjusting seat belt mechanisms, and advancing automobile design can significantly reduce the impact of collision-associated factors. Thus, through multidisciplinary approaches involving engineering, medicine, and public traffic policies, it is possible to implement measures that enhance occupant safety and decrease the incidence and severity of injuries resulting from automobile accidents.

AKNOWLEDGEMENTS

With gratitude, the authors express their sincere appreciation to Dr. Maria Clara Batista de Oliveira Medeiros, physician and professor at the Federal University of Rio Grande do Norte, for her academic support to the Academic League of Urgency and Emergency Medicine of Rio Grande do Norte (LAMURGEM-RN), an initiative led by students aimed at advancing and promoting scientific knowledge in this vital area of medical practice.