WOUND BALLISTICS WOUND BALLISTICS Rattaplee Pak-art, MD, FACS - PDF document

WOUND BALLISTICS WOUND BALLISTICS Rattaplee Pak-art, MD, FACS Department of Surgery Chulalongkorn University King Chulalongkorn Memorial Hospital The Thai Red Cross Society 1

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Available Kinetic Energy Mechanisms of Wounding: Treat the wound not the weapon MV 2 E K = ------------- 2 • Crush - laceration • Stretch - cavitation • Energy Expended • Blast • • All are the effect of a transfer of energy. 2 – V 2 2 ) M (V 1 • E EXP = ----------------------- • 2 Factors affecting the severity of projectile The velocity of the missile is the most significant The velocity of the missile is the most significant trauma: the projectile determinant of its wounding potential determinant of its wounding potential Shape: • bullets are aerodynamic, fragments are irregular • Low energy : knife or hand-energized missiles • Low energy : knife or hand-energized missiles (air friction) Construction: • metal jacket, hollow-tip; stability of bullet after • Medium energy : handguns • Medium energy : handguns impact; stress fragments bullet which creates secondary projectiles • High energy (>600 m/s) : military or hunting rifles • High energy (>600 m/s) : military or hunting rifles Stability in air: • range, age of weapon, temperature of barrel, interference in flight (ricochet) Bullet Case Powder Primer Pistol Revolver Rifle 3

เขาเล็ก ออกใหญ ?? Non-deforming rifle bullet: full metal jacket (FMJ) military bullet FMJ in soft tissue Full metal jacket rifle bullet (FMJ) in soft tissue QuickTime™ and a YUV420 codec decompressor are needed to see this picture. 4

Fragmented FMJ Fragmentation occur at point of Maximum Kinetic Energy transfer Entry and exit wounds: FMJ-bullet, rifle small entry hole small entry hole small exit hole small exit hole FMJ-Bullet Penetration of the shoulder small entry hole Entry Impact large exit Fracture Exit 5

Entry Entry Exit Remaining tissue Exit loss after excision and healing Semi-jacketed rifle bullet (SJ) Deforming and fragmenting in soft tissue: "dum-dum" rifle bullets: dum-dum Behaviour of projectiles FMJ Vs. SJ bullets Comparison FMJ- versus SJ-bullet same energy and same Equal transfer of kinetic energy scale Same volume cavity 6

Ricochet bullets Ricochet Effect on a bullet after collision with an obstacle • FMJ rifle bullet Ricochet: FMJ bullet Wound from ricochet 7

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Comparison FMJ-Bullet Bone injuries versus SJ-Bullet FMJ SJ FMJ SJ 9

Fragments Fragment in soap lightweight fast Same energy heavy Non deforming handgun Fragment wound lower leg bullet Handgun Deforming handgun bullets 10

Boundary effect Grazing gunshot of a 9 mm Luger FMJ Lead bullet full metal jacketed bullet 350 m/s 350 m/s 220 m/s 63 63 64 64 11

Tissue factors Factors affecting the severity of projectile trauma: the tissues • Tissue elasticity ; severity of damage • Excellent Tolerance ; Lung ,Skin • elastic properties of the tissues to which the • Good tolerance ; Skeletal muscle, Empty bowel wall energy transfer is applied: • Non-elastic ; Brain, Liver, Spleen, Kidney � Rupture • limiting boundaries of tissues: brain in • Fluid-fill organs ; Heart, Full bladder, Full cranium stomach, • Intestine ; may be rupture • Bone fracture from direct impact or energy transfer Red textile fibres transferred in a GSW retrograde direction are macroscopically visible Clean or Dirty Cavity Textile fiber Clinical applications Microscopic demonstration of displaced jeans fibres from the entrance region (blue) and the exit region (red) in a bullet track of series 1 at a distance of 15 cm from the bullet entrance site (×100 magnification) 12

Conclusions • High index of suspicion • Don’t believe what you see • Use knowledge guiding imagination 78 13