PHTLS Kinematics of Trauma — Questions and Answers

Question 1: According to Newton's first law as it applies to trauma, what happens to an unrestrained occupant when a vehicle suddenly stops?

The occupant stops simultaneously with the vehicle
The occupant continues moving at the same speed until acted upon by another force (Correct answer)
The occupant slows gradually due to friction
The occupant is pushed backward by the seat

Correct 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.

Question 2: The kinetic energy formula used in PHTLS to estimate energy transfer during trauma is:

KE = mass × velocity
KE = ½ × mass × velocity² (Correct answer)
KE = mass × gravity × height
KE = force × distance

Correct 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.

Question 3: In a frontal-impact motor vehicle collision, which injury pattern is associated with an unbelted driver who travels 'up-and-over' the steering wheel?

Lumbar spine compression and hip fractures
Head, neck, thorax, and face injuries (Correct answer)
Posterior rib fractures and renal contusions
Bilateral femur fractures and knee dislocations

Correct 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.

Question 4: Which injury pattern is most characteristic of the 'down-and-under' pathway in a frontal motor vehicle collision?

Facial lacerations and basilar skull fracture
Knee, femur, hip, and posterior acetabulum fractures (Correct answer)
Aortic tears and pulmonary contusions
Cervical spine hyperextension injuries

Correct 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.

Question 5: A patient was a restrained driver in a rear-impact collision. Which injury is most predictable based on kinematics alone?

Sternal fracture
Hyperextension cervical spine injury (Correct answer)
Splenic laceration
Bilateral pneumothorax

Correct 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.

Question 6: What does 'index of suspicion' mean in the context of PHTLS kinematics?

The probability that the patient is lying about the mechanism
Anticipating likely injuries based on the mechanism of injury even before they are confirmed (Correct answer)
A scoring system for scene safety threats
The likelihood of a secondary explosion at the scene

Correct 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.

Question 7: Which type of tissue absorbs the most kinetic energy during blunt trauma, making it most susceptible to injury?

Low-density tissue such as lung
High-density tissue such as solid organs and muscle (Correct answer)
Fatty tissue such as subcutaneous fat
Hollow viscus with gas such as bowel

Correct 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.

Question 8: A lateral (T-bone) impact MVC places the near-side occupant at highest risk for which injury pattern?

Bilateral femur fractures
Contralateral rib fractures and aortic shear
Ipsilateral rib fractures, clavicle fracture, lateral head impact, and pelvic fractures (Correct answer)
Anterior knee and patella fractures

Correct 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.

Question 9: Ejection from a vehicle during a crash is significant because:

Ejected patients always sustain spinal cord injury
The risk of death increases approximately 300% compared to non-ejected occupants (Correct answer)
Ejection protects the patient from interior vehicle deformation
Seat belt injuries are more severe than ejection injuries

Correct 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.

Question 10: A pedestrian struck by a vehicle typically experiences three phases of injury. What is the correct sequence?

Ground impact → vehicle impact → secondary vehicle impact
Vehicle bumper impact → hood/windshield impact → ground impact (Correct answer)
Windshield impact → bumper impact → ground impact
Airbag impact → hood impact → road impact

Correct 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.

Question 11: When evaluating a fall victim, which factor most reliably predicts severe injury potential?

Age of the patient
Surface the patient landed on
Height of the fall (Correct answer)
Whether the patient lost consciousness

Correct 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.

Question 12: Primary blast injury is caused by which mechanism?

Fragmentation projectiles striking the body
The overpressure wave passing through the body (Correct answer)
The body being thrown against a hard surface
Burns from the fireball

Correct 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.

Question 13: Cavitation in penetrating trauma refers to:

Air entering the pleural space through a chest wound
The temporary or permanent tissue displacement around the projectile path (Correct answer)
Collapse of small airways from blunt chest impact
Gas embolism from vascular injury

Correct 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.

Question 14: A motorcycle rider ejected during a crash who slides along the pavement sustains injuries primarily because of which kinematic principle?

Compression
Deceleration and friction energy exchange (Correct answer)
Rotational acceleration
Gravitational potential energy

Correct 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.

Question 15: How does a high-velocity rifle round produce more tissue damage than a low-velocity handgun round of the same caliber?

The rifle bullet has greater mass
The rifle bullet's higher velocity exponentially increases kinetic energy transfer and temporary cavitation (Correct answer)
The rifle bullet tumbles more during flight
The rifle bullet expands immediately upon leaving the barrel

Correct 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.

Question 16: Yaw and tumbling of a bullet after it enters tissue is significant because it:

Reduces penetration depth
Increases the surface area presented to tissue, dramatically increasing energy transfer (Correct answer)
Allows the bullet to seek vital organs
Prevents exit wound formation

Correct 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.

Question 17: Which PHTLS concept describes the brief window of time during which definitive hemorrhage control and surgical intervention can prevent death from trauma?

The platinum ten minutes
The golden period (Correct answer)
The critical hour
The resuscitation window

Correct 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.

Question 18: In a rollover vehicle collision, the greatest risk to unbelted occupants is:

Compression fractures from the roof crush
Ejection and subsequent ground impact (Correct answer)
Dashboard knee impact from repeated forward motion
Lateral rib compression from door intrusion

Correct 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.

Question 19: Secondary blast injury is caused by:

The overpressure wave striking gas-containing organs
Fragmentation and shrapnel striking the body (Correct answer)
The body being thrown and impacting surfaces
Burns from the thermal blast wave

Correct 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.

Question 20: A patient fell from a ladder and landed feet-first. Based on kinematics, which additional injuries should the provider suspect beyond calcaneus fractures?

Bilateral shoulder dislocations and brachial plexus injury
Tibial plateau fractures, hip fractures, pelvic fractures, lumbar spine compression, and wrist fractures (Correct answer)
Bilateral pneumothorax and tension hemothorax
Facial fractures and basilar skull fracture

Correct 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.

Question 21: Tertiary blast injury results from:

Inhalation of toxic gases released by the explosion
The patient being physically displaced and impacting a surface (Correct answer)
Penetrating fragmentation wounds
The overpressure wave disrupting hollow organs

Correct answer: The patient being physically displaced and impacting a surface

Tertiary blast injuries occur when the blast wind propels the victim's entire body and the person impacts the ground, a wall, or other surface, producing blunt trauma similar to a high-speed ejection.

PHTLS Kinematics of Trauma

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

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