Definition/Introduction
According to the Centers for Disease Control and Prevention (CDC), motor vehicle collisions (MVC) in 2013 accounted for over 2 million injuries and more than 32,000 deaths annually in the US.[1] The National Spinal Cord Injury Statistical Center cited that the most common cause of spinal cord injuries (SCI) in the US between the years 2010 and 2013 was MVCs, accounting for 38% of these injuries.[2][3]
Mechanism of Injury
Mechanism of injury (MOI) specifically refers to the method by which trauma and its associated forces directly or indirectly impact the human body. MOI implies a specific transfer of energy from one source (ie, the environment) to another (ie, the human body). These injury patterns assist in determining the extent of an injury and in the fundamental decision-making process for trauma triage guidelines. Energy transfer from the environment can result from a variety of causes. The intensity of the energy transfer will cause damage to the surrounding tissues, organs, muscles, and other body structures when it exceeds the body’s ability to resist such rapid, forceful energy changes.
According to the Law of Conservation of Energy, “Energy can neither be destroyed nor created, but it can change form.” This law goes to the essence of trauma. The kinetic, or moving, energy must be transferred to the impacted object. If a vehicle is traveling at high speed when it impacts an object, the impact force can be quadrupled. Spinal injuries may result from axial loads.[4][5][6]
Issues of Concern
Terminology
Kinematics: the actual or potential injuries realized by the human body
Biomechanics: refers to the actual force or impact imparted on the soft tissues and the body
Mechanism of injury: the exact cause of the injury and the implied transference of energy from one body to another (ie, from the environment to the human body)
All of these concepts ultimately impact trauma patients and their ultimate care. These 3 principles must guide accurate injury assessments. Kinetic and potential energy states are fundamental physics concepts that play a vital role in understanding energy potential. Energy is in a potential state when at rest and an active state when in motion. Once an object or mass becomes mobile, kinetic energy is formed. These principles can apply to a motor vehicle. The vehicle is in a potentially resting state. This vehicle is now traveling along at a certain speed and strikes a tree or immovable object. The vehicle is in motion, and kinetic energy transfer will play a role through an impact sequence.[7][8]
Impact Sequence
The first impact occurs when an immovable object strikes another object (such as a car vs. a tree, pole, another parked vehicle, or guardrail), causing the passengers to be launched forward violently. The second impact happens next when the car comes to an abrupt stop. The body then impacts with the inside of the car: the steering wheel, the windshield, the seatbelt or airbag, or the roadway or environment if ejected. Lastly, the third insult or impact to the body occurs when internal structures, such as organs and tissues, collide with the body cavities. For example, the aorta may tear as it propels into the thoracic cavity, or ribs may puncture a lung or spleen. Third impact or insults go to the essence of trauma assessment and determination of injuries based on this violent energy transfer. The mechanism of injury is vital in determining energy potentials and subsequent damage patterns based on the extent of those impacts.[4][9]
Impacts or Injury Patterns
Frontal and near-side collisions can result in steering wheel or dashboard impacts for front-seat passengers.
Head, neck, chest, and abdominal injuries are expected.
Suspect pulmonary contusions and rib fractures with front-end damage or near-side impact. Rib fractures tend to increase with age.
Patient weight and body mass index are positively correlated with the likelihood of injury.
Improperly worn safety belts or unrestrained individuals can add to the risk of lower extremity, pelvic, and abdominal trauma.
T-bone impacts can cause the occupant seated closest to the point of impact a multitude of problems with any intrusion.
Intrusion crushes the occupant, causing another impact, and if that’s not enough, they get a double hit by contact with the interior of the car and any personal items in the car.
T-Bone or lateral impacts are associated with aortic or organ shear injuries, as well as fractures of the pelvis, neck, clavicle, and skull on the impact side.
Rear impacts increase the risk of flexion and extension injuries of the neck and chance fractures of the spine.
Scene Assessment of Damage
A study conducted between 2007 and 2009 concluded that emergency medical services personnel do an excellent job of assessing rollover damage, but intrusion, deformity, and safety belt use can be difficult to judge on scene unless an experienced investigator is present. On scene, accurate assessments of damages and their correlation with injury potential are vital to the decision-making process regarding transfer to an appropriate tertiary care facility or trauma center. An adverse outcome may occur if transfer to a designated trauma center falls outside the golden hour of trauma. Trauma center designation involves state and local involvement in the process and requires sole triage criteria.[10]
Trauma Center Designation
The American College of Surgeons plays a valuable role in the evaluation and trauma center verification process. Trauma centers range from Level I to Level 5 designations. Trauma center readiness is key to the allocation of resources involved in a successful treatment plan, resuscitative care, and interprofessional of a complex trauma patient. Trauma care often takes on a multifaceted dimension with cultural, social, and community ramifications.
Trauma Triage Guidelines and Allocation of Resources
In conclusion, the mechanism of injury is the key to the successful creation of trauma triage guidelines through predictability of injury patterns and life-saving interventions. Studying injury patterns and population shifts provides valuable data to help alleviate circumstances leading up to motor vehicle crashes through prevention techniques, treatment changes, and legislation focused on reducing the potential for negative outcomes, as well as car manufacturer safety guidelines related to airbags and safety belts. In the future, aging populations will pose a challenge to the allocation of financial and medical resources for hospitals, long-term care facilities, and communities. Prevention, education, and legislation will have lasting ramifications for the healthcare continuum of the polytraumatized patient, with their basis in research, evidence-based practice, and policy changes. Reimbursement and fund allocation considerations will be a part of this decision-making process.[11]
Clinical Significance
Multisystem trauma involvement is clinically significant in that it should carry a high index of suspicion with t-bone collisions. Rollover crashes may cause all of these impacts as mentioned above and violent insults to the body. As the roof intrudes into the passenger compartment, head injuries are probable. If ejected, impact with the windshield, window, roadway, or another object on the road further complicates an already complicated patient. High-speed motor vehicle collisions, like those seen on the interstates, have a high probability of multisystem trauma involvement.[12][13]
