PHTLS Kinematics of Trauma 5 — Questions and Answers
Question 1: A rifle bullet causes a wound track larger than its diameter due to which kinematic phenomenon?
- Tumbling and yaw only
- Temporary cavitation from high-velocity energy transfer (Correct answer)
- Fragmentation of the bullet upon entry
- Hydrostatic shock limited to bone
Correct answer: Temporary cavitation from high-velocity energy transfer
High-velocity projectiles transfer energy rapidly to surrounding tissues, creating a temporary cavity that can be many times the bullet's diameter.
Question 2: Which of the following vehicle safety devices can cause injury if a patient is out of position at the time of deployment?
- Collapsible steering column
- Side curtain airbag deployed in a lateral crash
- Front airbag when the occupant is too close to the steering wheel (Correct answer)
- Pretensioner seatbelt
Correct answer: Front airbag when the occupant is too close to the steering wheel
An occupant positioned less than 10 inches from a deploying frontal airbag can sustain serious facial, thoracic, and upper extremity injuries.
Question 3: When assessing a patient involved in a rollover crash, why should the provider assume a higher injury severity even if the patient appears stable?
- Rollovers always cause spinal cord transection
- Multiple impacts occur in unpredictable directions, increasing the chance of unrecognized injuries (Correct answer)
- Insurance regulations require higher-level transport for rollovers
- Rollover patients always lose consciousness
Correct answer: Multiple impacts occur in unpredictable directions, increasing the chance of unrecognized injuries
During a rollover, occupants may sustain multiple impacts from different vectors with the vehicle interior, making injury prediction difficult and severity potentially high.
Question 4: In penetrating trauma, which wound characteristic is most consistent with a low-velocity injury?
- Large permanent cavity with significant surrounding tissue destruction
- Small entry wound with minimal surrounding tissue damage (Correct answer)
- Entry and exit wounds of equal size
- Significant temporary cavitation visible on imaging
Correct answer: Small entry wound with minimal surrounding tissue damage
Low-velocity weapons such as knives and handguns fired at close range cause damage primarily along the direct path of penetration with minimal cavitation.
Question 5: A child is struck by a car and found 30 feet from the point of impact. What does the distance of ejection primarily indicate?
- The child was thrown by another person after the accident
- The vehicle was traveling at high speed, predicting serious multisystem injury (Correct answer)
- The child's low body weight reduced impact force
- The striking vehicle had defective brakes
Correct answer: The vehicle was traveling at high speed, predicting serious multisystem injury
Greater ejection distance correlates with higher vehicle speed at impact, which directly predicts more energy transfer and more severe injuries.
Question 6: Which component of the PHTLS 'index of suspicion' is derived directly from kinematic analysis at the scene?
- Patient's chief complaint
- Predicted injury patterns based on mechanism and energy transfer (Correct answer)
- Vital signs obtained on patient contact
- Medical history reported by bystanders
Correct answer: Predicted injury patterns based on mechanism and energy transfer
The index of suspicion is the provider's anticipation of likely hidden injuries based on mechanism of injury and energy transfer principles before the physical exam.
Question 7: A patient in a rear-end collision reports neck pain. Which kinematic event explains the mechanism of cervical injury in rear impacts?
- The head is thrown forward into the steering wheel
- The torso accelerates forward while the unsupported head initially lags behind, causing hyperextension (Correct answer)
- The seatbelt locks and pulls the cervical spine posteriorly
- The headrest absorbs all energy, preventing injury
Correct answer: The torso accelerates forward while the unsupported head initially lags behind, causing hyperextension
In rear-end collisions, the torso is accelerated forward by the seat while the head momentarily remains stationary, producing rapid cervical hyperextension.
PHTLS Kinematics of Trauma 5
A rifle bullet causes a wound track larger than its diameter due to which kinematic phenomenon?