Penetrating Trauma

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Penetrating Trauma

• Markus Forsythe, MD

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Introduction to Penetrating Trauma

• 38,000 Deaths in US annually due to shootings.
• Mechanisms of penetrating trauma
• Knives, Arrows, Nails, etc
• Understanding principles of energy exchange
  increase the Index of Suspicion associated with
  the MOI

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Physics of Penetrating Trauma

• Recall Kinetic Energy Equation
• Greater the mass the greater the energy
• Double mass double KE
• Greater the speed the greater the energy
• Double speed 4x increase KE

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Physics of Penetrating Trauma

• Small Fast bullet can cause greater damage than
  large and slow.
• Different bullets of different weights traveling
  at different speeds cause
• Low Energy/Low Velocity
• Knives and arrows
• Medium Energy/Medium Velocity Weapons
• Handguns, shotguns, low-powered rifles
• 250-400 mps
• High Energy/High Velocity
• Assault Rifles
• 600-1,000 mps

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Physics of Penetrating Trauma

• Bullet spins as it travels down barrel
• Rifling in barrel
• Allows bullet to travel straight with slight yaw
• Bullet departs barrel, spinning with a slight
  wobble or yaw
• Weapon forced backward and absorbs energy
• Recoil

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Physics of Penetrating Trauma

• Remainder of energy propels bullet forward at a
  high rate of speed.
• Trajectory is curved due to gravity
• As bullet strikes object, it slows and energy is
  transferred to object.
• Law of Conservation of Energy

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Ballistics

• Study of the characteristics of projectiles in
  motion and effects upon objects impacted
• Factors affecting energy exchange between a
  projectile and body tissue
• Velocity
• Profile
• Stability
• Expansion Fragmentation
• Secondary Impacts
• Shape

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Energy Dissipation

• Drag
• wind resistance
• Cavitation
• formation of a partial vacuum and cavity within a
  semi-fluid medium
• Profile
• Size and shape of a projectile as it contacts a
  target
• Larger the profilegreater energy exchange
• Expansion and fragmentation results in damage
• Stability
• Allows for straighter trajectory
• Decreases after striking object results in
  tumbling

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Aspects of Ballistics

• Velocity
• Causes Trajectory
• Faster straighter trajectory
• Slower more curved due to gravity

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Aspects of Ballistics

• Profile
• Portion of bullet you see as it travels towards
  you
• Larger profile greater energy exchange
• Caliber
• Diameter of a bullet (ID of gun)
• 0.22 caliber 0.22 inches
• Bullets become unstable as they pass from one
  medium to another.

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Aspects of Ballistics

• Stability
• Bullet length increases bullet tumbling
• Can reduce the accuracy of the shot
• Reduced by Rifling in barrel (spinning)
• Yaw
• Gyroscopic effect on the center axis of the
  bullet that reduces tumbling
• Tumbling of bullet once it strikes object
• Reduces kinetic energy
• Greater tissue damage

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Bullet Gyroscopic Effect
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Aspects of Ballistics

• Expansion Fragmentation
• Results in increased profile
• Mushrooming
• Initial impact forces may result in fragmenting
• Greater tissue damage

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Trauma.org
Example of secondary projectile damage. Pt. shot
w/ small calibre, bullet did not enter cranial
vault. CT shows evidence of bony fragment damage
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Aspects of Ballistics

• Secondary Impacts
• Bullet striking other objects can cause yaw and
  tumble
• Body Armor (Kevlar)
• Transmits energy throughout entire vest resulting
  in blunt trauma
• Myocardial Contusion
• Pulmonary Contusion
• Rib Fractures
• Shape
• Handgun Ammunition Blunt Tumble
• Rifle Ammunition Pointed Piercing

Bullet striking Kevlar type vest
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Specific Weapon Characteristics

• Handguns
• Small caliber, short barrel, medium-velocity
• Effective at close range
• Severity of injury based upon organs damaged
• Rifle
• High-velocity, longer barrel, large caliber
• Increased accuracy at far distances
• Assault Rifles
• Large magazine, semi- or full-automatic
• Similar injury to hunting rifles
• Multiple wounds

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Specific Weapon Characteristics

• Shotgun
• Slug or pellets at medium velocity
• 00 (1/3) to 9 (pin head sized)
• Larger the load, the smaller the number of
  projectiles
• Deadly at close range
• Knives Arrows
• Low-energy low-velocity
• Damage related to depth and angle of attack
• Movement of the victim can increase damage

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Damage Pathway

• Projectile Injury Process
• Tip impacts tissue
• Tissue pushed forward and to the side
• Tissue collides with adjacent tissue
• Shock wave of pressure forward and lateral
• Moves perpendicular to bullet path
• Rapid compression, crushes and tears tissue
• Cavity forms behind bullet pulling in debris with
  suction.

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Damage Pathway

• Direct Injury
• Damage done as the projectile strikes tissue
• Pressure Shock Wave
• Human tissue is semi-fluid
• Solid and dense organs are damaged greatly
• Temporary Cavity
• Due to cavitation
• Permanent Cavity
• Due to seriously damaged tissue
• Zone of Injury
• Area that extends beyond the area of permanent
  injury

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Ballistics Cavitation
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Much of the damage done by a bullet results from
the tumbling motion and the cavitation in the
tissue. This is the bullet track in clay of a .38
caliber round, demonstrating that the wound track
is much larger than .38 inches (closer to 3
inches).
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Low-Velocity Wounds

• Objects
• Knives, Ice-picks, Arrows
• Flying objects or debris
• Injury limited to tissue impacted
• Object pathway
• Object twisting or moved
• Oblique angle
• Attacker Characteristics
• Males outward and crosswise
• Females overhand and downward

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Specific Tissue Organ Injuries

• Density of tissue affects the efficiency of
  energy transmission
• Resiliency
• Strength and elasticity of an object
• Connective Tissue
• Absorbs energy and limits tissue damage
• Organs
• Solid Organs
• Dense and low resilience
• Hollow Organs
• Fluid filled transmit energy increased damage
• Air filled absorbs energy less damage

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Specific Tissue Organ Injuries

• Lungs
• Air in lung absorbs energy
• Parenchyma is compressed and rebounds
• Pneumothorax or hemothorax can result
• Bone
• Resists displacement until it shatters
• Alters projectile path

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General Body Regions

• Extremities
• Injury limited to resiliency of tissue
• 60-80 of injuries with lt10 mortality
• Abdomen (Includes Pelvis)
• Highly susceptible to injury and hemorrhage
• Bowel perforation 12-24 hrs peritoneal
  irritation
• Thorax
• Rib impact results in explosive energy
• Heart great vessels have extensive damage due
  to lack of fluid compression
• Any large chest wound compromises breathing

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General Body Regions

• Neck
• Damages Trachea and Blood Vessels
• Neurological problems
• Sucking neck wound
• Head
• Cavitational energy trapped inside skull
• Serious bleeding and lethal

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Wound Characteristics

• Entrance Wounds
• Size of bullet profile for non-deforming bullets
• Deforming projectiles may cause large wounds
• Close Range
• Powder Burns (Tattooing of powder)
• 1-2 mm circle of discoloration
• Localized subcutaneous emphysema
• Exit Wounds
• Appears to be Blown outward
• Pressure wave

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Special Concerns with Penetrating Trauma

• Scene Size-Up
• Law-Enforcement
• DO NOT ENTER UNTIL SCENE IS SAFE!
• Weapons Victim or Assailant
• Assailants
• IF A CRIME SCENE
• DOCUMENT
• DO NOT DISTURB EVIDENCE
• RETAIN CLOTHING, ETC
• LIMIT PERSONNEL INVOLVEMENT

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Special Concerns with Penetrating Trauma

• Penetrating Wound Care
• Facial Wounds
• Difficult intubations
• Depress chest
• Pass ET through bubbling tissue
• Consider Cricothyroidotomy
• Chest Wounds
• Pneumothorax
• 2/3 the diameter of the trachea or larger to
  entrain air
• 3-sided occlusive dressing
• Needle Decompress
• Pericardial Tamponade

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Special Concerns with Penetrating Trauma

• Impaled Objects
• Low-energy
• Dangerous to remove
• DO NOT REMOVE
• UNLESS
• In Cheek
• Interferes with CPR ASSESS!!!

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Trauma.org
Image of a drag racer who lost control and hit a
chainlink fence traveling backwards. The toprail
pipe on the fence entered the rear of the car and
impaled his posterior pelvic region. The patient
was alert and stable. The medics used the jaws to
cut the pipe to a manageable length and
transported the patient. The pelvis was stable,
distal pulses were normal, and the abdomen and
rectal were negative. Plain radiography was
normal except for the foreign body.