BALLISTICS IN PENETRATING TRAUMA CDR JOHN WEI, USN MC MD 4th Medical Battallion, 4th MLG BSRF-12

OBJECTIVES Types of penetrating trauma Commonly encountered injuries Basic ballistics Expected wounds, operative planning, and treatment

TYPES OF PENETRATING TRAUMA GSW Rifle Pistol Shot gun Stab Blast

MECHANISM OF INJURY Body and tissue trauma associated with cause of wounding ~500,000 gsw/year in USA Risk of death and functional deficit Surgical planning and treatment of wound

DEFINITIONS Ballistics Internal ballistics External ballistics The science of mechanics that deal with the flight, behavior, and effects of projectiles Internal ballistics The study of processes originally accelerating the projectile External ballistics The study of the projectile as it passes through space Terminal ballistics The study of the interaction of the projectile with its target

INTERNAL BALLISTICS

DEFINITIONS Muzzle velocity Velocity of the round as it leaves the barrel end Kinetic energy (J) = 1/2 mass(kg) x velocity(m/sec)2 - 1 ft-lb= 1.3558 J, 1 grain=0.0648 grams -High velocity (rifle) vs. Low velocity (pistol) Permanent vs temporary cavity Ballistic coefficient- friction/drag of air against projectile -based on shape and weight of projectile Caliber- bullet diameter in inches (ie .22, .45) Gauge- diameter of shotgun barrel (ie 12 ga.)

WOUND BALLISTICS Ballistic wound research in gelatin forms Yawing and cavitation do not cause as severe tissue trauma as fragmentation Temporary stretch cavitation in which tissue is pushed by the shock wave following the projectile

GUN SHOT WOUNDS Type of weapon / bullet used Distance from weapon Location and trajectory/path of injury Permanent vs temporary cavity

ENERGY OF DIFFERENT CALIBER PROJECTILES .22 170J (m = 36g, v = 350 m/sec) .223 1550J (m = 50g, v = 900 m/sec) .38 325J (m =120g, v = 300 m/sec) 7.62 3500J (m=165g, v=850 m/sec)

PERMANENT AND TEMPORARY CAVITATION Permanent: tissue crush and excavation Temporary: blast effect due to tissue stretch

MAXIMAL TEMPORARY CAVITY DIAMETERS .22 (170J) 4.0 -5.0 cm .38 (325J) 4.0 -8.3 cm .223 (1550J) 13.0 -14.0 cm 7.62mm (3500J) 17.0 -23.0 cm

BALLISTIC GEL CAVITATION

BULLET TYPES Full metal jacket Lead Softpoint, semi jacketed Hollow point, ballistic tips

BULLET FRAGMENTATION Increased tissue destruction compared to temporary cavity Hague convention of 1899 Restrictions on use of expanding/fragmenting bullets

COMMON BULLETS .22 caliber Hand pistol Cheap and readily available Low energy, lead bullet Tumble tissue kinetics

.22 BULLET WOUND

COMMON BULLETS .38 caliber Pistol Low velocity

.38 BULLET WOUND

COMMON BULLETS 7.62 x 39 AK-47, military use High velocity Increased injury and tissue damage

COMMON BULLETS 30-06 Rifle Common hunting round Old military use Fragmenting bullets Old military use

SHOTGUN “bird shot” Multiple low energy spreading pellets, short range effect “buck shot” Fewer larger pellets Slug Single projectile, longer effective range

SHOTGUN BALLISTICS

SHOTGUN WOUND

KNIFE TRAUMA Types Penetrating stabbing Soft tissue slash and cutting

KNIFE TRAUMA Type and length of knife Identify all external injuries Determine potential internal injuries Patient stabilization and life support Local wound exploration, x-ray imaging, operation if needed

IMPALEMENT INJURIES Physical exam of neurologic and vascular function Radiologic studies to determine anatomic injuries and bony fractures Removal of object in operating room and repair of damaged structures

EXPLOSIVE BLAST INJURIES Primary Blast wave effect Secondary shrapnel Tertiary fall or landing blunt injury Other Burn, inhalation, smoke

EXPLOSIVE BLAST INJURIES

EXPLOSIVE BLAST INJURIES Dominant cause of mortality and injury in current military actions Large amount of tissue damage from explosive blast Penetrating wounds from metal shell fragments, stones, human bones, automotive parts

EXPLOSIVE BLAST INJURIES Primary projectiles from original explosive device: mortar round, grenade, or improvised explosive device Secondary missiles from environment Penetrating wounds complicated by gross contamination and massive tissue injury Ballistics and trajectories unpredictable

EXPLOSIVE BLAST INJURIES

CONCLUSIONS Knowledge of mechanisms of wounding Ballistics and kinetics help to diagnose and plan treatment of injuries Associated injuries or wounding patterns from known mechanism should be looked for