Trauma History, Past Medical History, Medications and Allergies

Mechanism of Injury and Index of Suspicion in Vehicular Trauma

In emergency medical care, the mechanism of injury describes the forces, energy transfer, and motion that caused damage to the patient. Whenever an emergency medical technician evaluates a trauma scene, observing these physical forces allows the provider to develop a high index of suspicion. A high index of suspicion is the anticipation of potential unseen injuries based on the mechanism of injury. For instance, when a vehicle strikes a concrete barrier, the physical destruction of the car provides clear evidence regarding the magnitude of kinetic energy directed into the passenger compartment.

In motor vehicle collisions, three successive impacts occur: the vehicle collision, the human collision, and the internal organ collision. First, the vehicle strikes an object and abruptly stops. Second, the unrestrained or restrained occupant continues moving until striking the vehicle interior or safety restraints. Third, the patient's internal organs continue traveling forward until colliding with the internal skeletal frame and muscular walls of the body cavities. These internal impacts can produce severe organ tears, bleeding, or bruising that are completely hidden from plain sight during an initial visual inspection.

The direction of the impact determines predictable injury pathways. Frontal impact motor vehicle collisions commonly produce either an up-and-over or down-and-under injury pathway. In an up-and-over pathway, the occupant moves upward over the steering wheel, frequently resulting in head, neck, chest, and abdominal injuries from striking the steering wheel or windshield. Conversely, a down-and-under pathway causes the occupant's lower body to slide forward, where the knees, femurs, hips, and pelvis suffer injuries from striking the dashboard.

Other collision types create distinct physical patterns. Lateral collisions can cause injuries to the head, neck, chest, abdomen, and pelvis, particularly on the side of impact. Rear-end collisions commonly cause cervical spine hyperextension and hyperflexion injuries as the torso is thrust forward while the head lags behind. Rollover collisions can produce unpredictable multisystem injuries because the occupant experiences multiple impacts at various angles, especially if an occupant is ejected. Patient ejection from a vehicle dramatically increases the risk of severe injury and death. Inside the cabin, physical damage tells an important story: a deformed steering wheel or starred windshield indicates significant force transmission to the patient's torso or head. Furthermore, deployment of an airbag does not eliminate the risk of cervical spine injury or occult blunt trauma, and seatbelts worn improperly above the iliac crests can cause severe compression injuries to abdominal organs and lumbar spine fractures.