The study of road accidents shows that the use of seat belts affects the type and severity of injuries. The vast variety of typical injuries related to wearing a seat belt is united under the name “seat belt trauma”. It includes soft tissue injuries, the locomotor system, and internal organs, arising from the process of “restraining” of the body by the belt (Chandler et al. 1997; Dehner 1971; Greingor and Lazarus 2006). Some of the very common disabilities are so called “whiplash” spinal cord injuries. They include different severity of damages in joint-ligament, bone structures, spinal cord, or cartilage intervertebral discs of the spine when the borders of normal physiological movements are crossed (Huelke et al. 1995; Huelke and Kaufer 1975). Due to the use of the most common 3-point seat belts of the “lap-shoulder” type, whiplash disabilities affect most often the cervical spine. In case of a sudden stop of the vehicle or a frontal impact, the head sharply continues its forward motion based on the physical law of conservation of energy. Depending on the value of the deceleration, the relative weight of the head can be increased many times. This causes hyperflexion (bending forward) in the cervical spine and leads to its disability (Saukko and Knight 2004; Ali and Giddins 2008).
The presented case is a very unusual variant of damage of spine and related to it anatomical structures under the influence of the transmission of forces applied to the body, as a result of a frontal collision at high speed when the driver of a car is restrained by a seat belt. The damage is in the thoracolumbar region of the spine. This location is most commonly obtained by the use of horizontal 2-point belts (lap-type), when a frontal impact causes a forceful hyperflexion. Rouhana et al. (2003) described that the 4-point belt in front impacts appeared to shift load to the clavicles and pelvis and to reduce traction of the shoulder belt across the chest, resulting in a reduction in chest deflection by a factor of two. This is associated with a 5- to 500-fold reduction in thoracic injury risk, including the thoracic part of the vertebral column. Based on their survey in four of six post mortem examinations, human subjects restrained by 4-point belts during 40 km/h sled tests, chest compression was zero or negative, and the fractures were nearly eliminated. In general the effect of 4-point seat belt is associated with the ability to prevent submarining under the lap.
The cause of death was acute massive blood loss due to traumatic rupture of the abdominal aorta associated with a fracture of the 10th thoracic vertebra. The mechanism of the injury to the aorta relates to the biomechanical forces incurred on the abdominal aorta, which is tethered between the spinal column and the peritoneum and abdominal viscera. These forces disrupt the intima and, depending on the magnitude of force, can lead to aortic transection (Shalhub et al. 2012). Incorrectly adjusted straps allow the body to move forward and cause a violent hyperextension of the thoracolumbar spine (submarining). Thus, it is possible that the damage to the aorta may be caused by the ragged ends of the fractured spine tearing the aorta which is stretched over it. Simultaneous abdominal injuries and vertebral fractures were initially described in 1962 as a “seat belt syndrome”. Dajee described the “seat belt aorta” as the injury to the aorta by a seat belt during a collision (Dajee et al. 1979).
The cause of the trauma may be identified by the comparison and analysis of all data obtained—the mechanism of the accident, age, sex, body mass index, anthropometric characteristics, and the type and location of injuries. The nature and severity of injuries and their consequences are varied and are determined in each specific situation of the technological parameters of the car, the speed of the terrain and road conditions, driving skills, anatomical characteristics of victims, and others (Reagan 1995). They built laboratory scale models or make computer dynamic simulators, which set a maximum number of manageable parameters—some constant, and other variables in order to simulate controlled, but most real situations that can be modeled, photographed, and studied in details (Yang et al. 2006). In our case, the trunk and especially abdominal region of the driver were extremely massive and heavy, with increased fat. The stomach was extended and filled with food. His age and the mass of the body determine the reduced resistance to dynamic loads and mostly in the spine according to the facts that there is a 10% loss of skeletal muscle mass by the age 50 years and the kinetic energy is dependent on the mass and velocity. In addition, the pressure of adjacent organs, which was transmitted to the abdominal wall, was also very high, proportionally to their weights.
The position of the seat belt sign was atypical, which showed the “submarining” of the body during the car accident. The lower part held the pelvis to the seat. The upper oblique part, raised high above the abdomen, held the upper part of the chest and shoulder girdle to the seat back. The bloated and heavy abdominal area was between them, free to move forward as submarining under the diagonal component of the 3-point strap. The concrete evidence of this motion was the presence of the fracture of the thoracic vertebra. Although the seat belt was placed, the driver was not actually restrained. Thus, the presence of atypical position of the seat belt sign and overweight were the predictors of severe blunt abdominal trauma. The presence of the “seat belt mark” sign should alert the physician to the high likelihood of specific internal injuries (Velmahos et al. 1999).
Some anthropometric characteristics of injured persons or incorrectly positioned straps can increase the danger of injury. Where the person is too small for the harness, such as a child or a small woman, the body may slide from under the strap (submarining)—or it may act as a garrote around the neck. Pregnant women also have problems with belts (Saukko and Knight 2004). They represent high-risk groups who are particularly vulnerable to injuries resulting from inappropriate seat belt application, and the opportunity for education on seat belt application should not be missed in all healthcare contacts (Masudi et al. 2017) because of their body disproportions, as in our case.