Trauma

Three fundamental mechanisms of trauma (NIH/NIHS)

1. Blunt
2. Penetrating
3. Deceleration

Blunt trauma definition and common scenarios

Force applied over a broad surface while skin remains intact.

Common Scenarios:

• Motor vehicle collisions (MVCs)
• Falls
• Pedestrian strikes

Three force vectors in blunt trauma and their corresponding injuries

• Compression: Organ contusion
• Shear: Vessel tear
• Torsion: Pelvic fracture

Deceleration trauma mechanism and clinical deception

Occurs when the body stops moving while internal organs continue moving forward, causing tearing at anatomical attachment points. Clinically deceptive because patients can initially present as stable before suddenly deteriorating hours later.

Four classic deceleration injury sites and their anchor points

1. Aorta: Ligamentum arteriosum
2. Spleen: Splenic hilum
3. Liver: Hepatic veins
4. Brain: Grey-white matter junction

Low- vs. high-velocity penetrating trauma

• Low-velocity threshold: $< 350\,\text{m/s}$
• High-velocity threshold: $> 600\,\text{m/s}$
• Kinetic Energy Formula: $KE = \frac{1}{2}mv^2$
• Damage mechanism: Velocity is squared, meaning high-velocity projectiles create temporary cavitation that damages tissue far beyond the projectile tract.

Permanent vs. temporary cavitation

• Permanent Cavitation: The actual tract carved by the projectile.
• Temporary Cavitation: A pressure wave reaching $10$ to $30$ times projectile diameter, causing delayed tissue necrosis.
• Clinical Relevance: Temporary cavitation is the most critical factor when determining surgical debridement.

Mechanism of contralateral organ injury in lateral impacts

The body shifts rapidly sideways, crushing contralateral organs against the spine.

• Left-side impact: Spleen injury
• Right-side impact: Liver injury

Up-and-over vs. down-and-under frontal crash trajectory patterns

• Up-and-over: Motion over the steering wheel causing injuries to the head, chest, and abdomen.
• Down-and-under: Motion downward into dashboard causing knee impact transmitted to hips, leading to posterior hip dislocation.

Signature deceleration injury in the thorax and exact location

Thoracic aortic transection, occurring $5\,\text{cm}$ to $10\,\text{cm}$ distal to the left subclavian artery at the ligamentum arteriosum.

Q1: Name the 3 fundamental mechanisms of trauma per NIH/NIHS

A: Blunt, Penetrating, Deceleration

Q1: Name the 3 fundamental mechanisms of trauma per NIH/NIHS

A: Blunt, Penetrating, Deceleration

Q1: Name the 3 fundamental mechanisms of trauma per NIH/NIHS

A: Blunt, Penetrating, Deceleration

Q1: Name the 3 fundamental mechanisms of trauma per NIH/NIHS

A: Blunt, Penetrating, Deceleration