PHTLS Kinematics of Trauma 2 — Questions and Answers
Question 1: 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 2: 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 3: 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 4: 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 5: 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 6: 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 7: 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.
PHTLS Kinematics of Trauma 2
A lateral (T-bone) impact MVC places the near-side occupant at highest risk for which injury pattern?