Kinematics of Trauma Flashcards

According to Newton's first law as it applies to trauma, what happens to an unrestrained occupant when a vehicle suddenly stops?

Answer: The occupant continues moving at the same speed until acted upon by another force

Newton's first law states that an object in motion stays in motion; an unrestrained occupant continues forward at the pre-impact speed until struck by the dashboard, steering wheel, or windshield.

The kinetic energy formula used in PHTLS to estimate energy transfer during trauma is:

Answer: KE = ½ × mass × velocity²

KE = ½mv² demonstrates that velocity has a squared effect on kinetic energy, meaning doubling speed quadruples the energy that must be absorbed by body tissues.

In a frontal-impact motor vehicle collision, which injury pattern is associated with an unbelted driver who travels 'up-and-over' the steering wheel?

Answer: Head, neck, thorax, and face injuries

The up-and-over pathway directs the body toward the steering wheel and windshield, commonly causing head, facial, cervical spine, and thoracic injuries.

Which injury pattern is most characteristic of the 'down-and-under' pathway in a frontal motor vehicle collision?

Answer: Knee, femur, hip, and posterior acetabulum fractures

In the down-and-under pathway the knees impact the dashboard, transmitting force up the femur to the hip and posterior acetabulum, producing a predictable lower-extremity and pelvic injury pattern.

A patient was a restrained driver in a rear-impact collision. Which injury is most predictable based on kinematics alone?

Answer: Hyperextension cervical spine injury

Rear impacts cause rapid forward acceleration of the torso while the unsupported head lags behind, producing hyperextension stress on the cervical spine.

What does 'index of suspicion' mean in the context of PHTLS kinematics?

Answer: Anticipating likely injuries based on the mechanism of injury even before they are confirmed

Index of suspicion means maintaining awareness of probable injuries predicted by the energy exchange and mechanism so treatment is not delayed waiting for symptoms to manifest.

Which type of tissue absorbs the most kinetic energy during blunt trauma, making it most susceptible to injury?

Answer: High-density tissue such as solid organs and muscle

High-density, inelastic tissues such as solid organs and muscle cannot deform as readily and therefore absorb more energy per unit volume, resulting in greater injury.

A lateral (T-bone) impact MVC places the near-side occupant at highest risk for which injury pattern?

Answer: Ipsilateral rib fractures, clavicle fracture, lateral head impact, and pelvic fractures

A lateral impact drives the door into the near-side occupant, causing ipsilateral rib, clavicle, and pelvic fractures as well as direct lateral head trauma from the window or door pillar.

Ejection from a vehicle during a crash is significant because:

Answer: The risk of death increases approximately 300% compared to non-ejected occupants

Ejection exposes the patient to a second, uncontrolled impact with the ground or other objects, increasing the mortality risk roughly threefold compared to remaining inside the vehicle.

A pedestrian struck by a vehicle typically experiences three phases of injury. What is the correct sequence?

Answer: Vehicle bumper impact → hood/windshield impact → ground impact

The bumper first strikes the legs or pelvis, the hood and windshield then impact the torso and head as the pedestrian is thrown up, and finally the ground impact occurs when the body falls.

When evaluating a fall victim, which factor most reliably predicts severe injury potential?

Answer: Height of the fall

Gravitational potential energy (mgh) increases directly with height, so fall height is the primary kinematic predictor of energy transfer and injury severity.

Primary blast injury is caused by which mechanism?

Answer: The overpressure wave passing through the body

The primary blast wave produces a rapidly changing overpressure that damages air-fluid interfaces — particularly in the lungs, ears, and bowel — without external physical contact.

Cavitation in penetrating trauma refers to:

Answer: The temporary or permanent tissue displacement around the projectile path

As a projectile passes through tissue it displaces tissue radially, creating a temporary cavity larger than the projectile itself; inelastic organs like the liver suffer greater permanent damage than elastic tissue like muscle.

A motorcycle rider ejected during a crash who slides along the pavement sustains injuries primarily because of which kinematic principle?

Answer: Deceleration and friction energy exchange

Sliding creates friction-based energy exchange between the rider and the road surface, producing abrasions and degloving (road rash) as kinetic energy is dissipated across the skin.

How does a high-velocity rifle round produce more tissue damage than a low-velocity handgun round of the same caliber?

Answer: The rifle bullet's higher velocity exponentially increases kinetic energy transfer and temporary cavitation

Because KE = ½mv², doubling velocity quadruples kinetic energy, allowing high-velocity rounds to transfer far more energy to tissue and produce much larger temporary cavities.

Yaw and tumbling of a bullet after it enters tissue is significant because it:

Answer: Increases the surface area presented to tissue, dramatically increasing energy transfer

When a bullet yaws or tumbles it presents a larger cross-sectional area to surrounding tissue, increasing drag and energy transfer and creating a larger wound channel.

Which PHTLS concept describes the brief window of time during which definitive hemorrhage control and surgical intervention can prevent death from trauma?

Answer: The golden period

The 'golden period' (historically 'golden hour') represents the time-sensitive interval after injury when aggressive intervention can prevent progression to irreversible shock and death.

In a rollover vehicle collision, the greatest risk to unbelted occupants is:

Answer: Ejection and subsequent ground impact

Rollovers dramatically increase the risk of partial or complete ejection; ejected occupants face a second, high-energy ground impact with a mortality risk three times higher than restrained occupants.

Secondary blast injury is caused by:

Answer: Fragmentation and shrapnel striking the body

Secondary blast injuries result from fragments and shrapnel propelled by the explosion striking the patient, producing penetrating trauma similar to gunshot or stab wounds.

A patient fell from a ladder and landed feet-first. Based on kinematics, which additional injuries should the provider suspect beyond calcaneus fractures?

Answer: Tibial plateau fractures, hip fractures, pelvic fractures, lumbar spine compression, and wrist fractures

Axial loading from a feet-first fall transmits force up the skeletal column, producing a predictable chain of calcaneus, ankle, tibial plateau, hip, pelvic, and lumbar spine injuries, with wrist fractures from outstretched hands.