Published on February 28, 2008
Myth and Mechanisms of Firearm Injuries: Myth and Mechanisms of Firearm Injuries Dr. Joel Turner, CCFP, FRCP 3 McGill University January 12, 2000 Slide3: "A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed” 2d Amendment to the U.S. Constitution Slide7: Objectives: 1. Epidemiology of Firearm-related injuries/deaths 2. Basic anatomy and terminology 3. Ballistics of firearms 4. Role of the EP Slide8: 1. Epidemiology/Statistics Firearm death rate (per 100,000) for young males in 12 selected countries (Center for Disease Control. Births & Death, 1995) Slide9: In 1997, -68% of all homicides caused by gun 92% among young blacks 86% of all suicides caused by gun Number of non-fatal GSW ranges from 140,000 to 200,000 / year 17,000 / year are treated in ED’s for unintentional GSW Just the facts…. Voelker R. JAMA, 1995 Hayert, et al. Natl Vital Stat Reports, 1999 Sinauer, et al. JAMA, 1996 Slide10: Firearms Deaths (per 100,000) by Mode of Death for Children <15 Years of Age - Top 10 Countries C.D.C. Rates of Homicide, Suicide, and firearm- Related death among children. MMWR, 1997 -Firearms are the 2nd leading cause of death of children in the U.S. Number 1 cause of death in young blacks Slide11: Canadian numbers… United States Canada (Hurg K, Firearm Statistics. Dept of Justice, March, 1999) Slide12: Canadian numbers… (Canadian Firearm Centre- Statistics Canada) Slide13: Canadian numbers… (Canadian Firearm Centre – Angus Reid Group, May 1998) Slide14: Canadian numbers… (Canadian Firearm Centre- Statistics Canada. Homicide Survey, 1997) Slide15: 1989-1995: 9,995 people shot in Washington State -29% ED care only -29% Admitted to hospital & survived -42% died Hospital Visits and admissions 1988-1996: average 1,217 admissions/year Canada: Quebec: 1988-1996: average 287 admissions/year (23.6%) 43.6% - firearm accidents 28.2% - self-inflicted 22.0% - inflicted by others (Cummings, et al. Annals of Emergency Medicine, 1998) (Canadian Institute for Health Information) Slide16: 2. Terminology & Anatomy of Firearms A. The Gun: Slide17: Action Chamber Barrel Rifling Bore Caliber Muzzle Hammer Magazine (Clip) Anatomy of the Gun Slide18: The Guns Handguns Single shot weapons (target pistol) Derringer Revolver Semi-automatic pistol 2. Rifles 3. Shotguns 4. Fully automatic Slide19: The derringer Slide20: The Revolver Slide21: Semi-automatic pistol Slide22: Rifles Slide23: Shotguns Slide24: Anatomy of the Cartridge Shotgun Handgun Rifle Primer Flash Hole Powder bullet Powder Primer Wad Shot Slide25: Small arms powder made of: 1. Nitrocellulose base, or 2. Nitrocellulose / nitroglycerine mix -Smokeless powder is NOT an explosive (black powder IS) -Grains come in different shapes and sizes -The smaller the grain the faster it burns Some Powder basics: Slide27: 3. Ballistics of firearms. Science of travel of projectile in flight Divided into 3 parts: Internal (travel within the gun) External (gun to target) Terminal (wound ballistics) Slide28: BANG! (what happens when the trigger is pulled?) Primer fires Intense flame created by primer fills chamber Powder burns, creates large gas expansion Huge pressure generated pushes bullet -The more complete and instant the burning, the more efficient the expansion of gas The tighter the hold of the bullet in the cartridge, The tighter the fit in the bore, the more efficient use of the gas I. Internal Ballistics – what affects what? Slide29: A little bit of physics… I. Internal Ballistics – what affects what? Slide30: II. External Ballistics – gun to target Slide31: II. External Ballistics – gun to target Slide32: III. Terminal Ballistics – Wound Ballistics What happens when the bullet hits the target? Slide33: Bullets produce damage in 3 ways: 1. Laceration and crushing 2. Cavitation: a) permanent cavity: b) temporary cavity. (tissue splash) 3. (Shock waves) (U.S. Dept of Defense) III. Terminal Ballistics – Wound Ballistics Slide34: IV. Wounding mechanisms – Wound Profiles Many tissue simulants have been tried, few are accurate (eg: animals, clay, soap, water-soaked phone books...). Valid tissue simulant – 10% Ordnance Gelatin Calibrated against various living animal tissue Shots into this substance wound profiles Accuracy verified by comparing with human autopsies. Now: Scientifically valid measurement tool Different projectile effects can be compared. Principles of wound ballistics can be studied. Can predict wounding potential of various projectiles. Fackler, et al. J Trauma. 1985 Fackler, et al. Wound Ballistics Review. 1994 Slide35: .32 Cal. Silvertip Winchester -soft lead -Non-fragmenting, expanding -Velocity: 940 fps (similar to present day .22 cal) Neck A. Handguns and Rifles IV. Wounding mechanisms – Wound Profiles Fackler, et al. Annals of Emergency Medicine. 1996 Slide36: M-80 7.62 mm NATO cartridge: -Full Metal Jacket -Non-fragmenting, Non-expanding -Velocity = 2800 fps IV. Wounding mechanisms – Wound Profiles Slide37: Mannlicher Carcano 6.5 mm -Full metal Jacket -Non-deforming, Non-fragmenting -Velocity = 2085 fps IV. Wounding mechanisms – Wound Profiles Slide38: .45 Cal Automatic pistol - full metal jacket - velocity = 870 fps IV. Wounding mechanisms – Wound Profiles Slide39: M-16 .22 Cal Military Rifle -Full Metal Jacket -Fragmenting rifle bullet -Velocity = 3035 fps IV. Wounding mechanisms – Wound Profiles Slide40: Winchester .308 Caliber Hunting Rifle (civilian) -civilian equivalent of military M-16 -Soft Point bullet -Fragmenting bullet -Velocity = 2,900 fps IV. Wounding mechanisms – Wound Profiles Slide41: B. Shotguns 12 gauge shotgun - 1 oz slug - Velocity = 1510 fps IV. Wounding mechanisms – Wound Profiles Slide42: 12 gauge shotgun - 27 pellet #4 buck shot - Velocity = 1350 fps IV. Wounding mechanisms – Wound Profiles Slide43: 12 gauge Shotgun -169 pellets, #4 shot - Velocity = 1200 fps IV. Wounding mechanisms – Wound Profiles (Letterman Army Institute of Research) Slide44: IV. Wounding mechanisms – Wound Profiles Slide45: V. Myths of Firearm Injuries and Wound Ballistics: a) Myth of High Velocity: False dogma: 1. Tissue damage is directly related to bullet velocity. 2. High vel. missile injuries require aggressive resection. 3. Low vel. missile injuires require little or no treatment. 1960’s – Vietnam war, introduction of M-16 rifle (bullet speed = 3100 fps): - GSW severity increased significantly - The M-16: “massively destructive” “devastating wounding power” - High velocity became synonymous with “devastating killing power” Rich, et al. JAMA. 1967 Dimond, et al. J Trauma. 1967 Slide46: 1974 – Rybeck, et al. - High vel. Injuries cause temporary cavity 30x diameter of missile. - this tissue “would not survive” - core of tissue would have to be excised!! - equates to an amputation of almost any wound to arm/leg a) Myth of High Velocity…. V. Myths of Firearm Injuries and Wound Ballistics: 1975 -The Nato Handbook: Emergency War surgery (U.S. Govt. Printing Office) Rybeck, et al. Acta Chir Scand. 1974 Slide47: V. Myths of Firearm Injuries and Wound Ballistics: BUT: History of small arms development shows us differently: -Late 1880’s largest increase in vel. of small arms projectiles. - From 1,100 to 2,400 fps - Invention of smokeless gun powder and jacketed bullets - striking decrease in wounds severity reported from all battlefields !! Slide48: .38 Special Velocity = 880 fps Remington .357 Magnum Velocity = 1400 fps V. Myths of Firearm Injuries and Wound Ballistics: Despite the 60% increase in velocity, the shape and size of both temporary and permanent cavities are very similar, Fackler, Emergency Medicine Clinics of North America. 1998 Slide49: M80 7.62 mm NATA cartridge Velocity = 2800 fps M-16 .22 Cal Military Rifle Velocity = 3035 fps V. Myths of Firearm Injuries and Wound Ballistics: Despite similar velocities, M-16 produces significantly more injury. Bullet fragmentation is predominant reason for M-16’s increased tissue disruption Fackler, Emergency Medicine Clinics of North America. 1998 Slide50: b) Shock waves and Injury V. Myths of Firearm Injuries and Wound Ballistics: 1940’s: Harvey, et al. Surgery. 1947 1980’s: Suneson, et al. J Trauma. 1987, 1988, 1989 1990’s: Ordog, et al. J Trauma. 1994 Present day lithotriptor: Slide51: V. Myths of Firearm Injuries and Wound Ballistics: c) “sterility” of bullets High temperatures inside gun barrel DO NOT sterilize bullets ALL gunshot wounds are contaminated. Use of antibiotics has virtually wiped out beta-hemolytic strep from battlefields (major cause of mortality prior to use of penicillin) Slide52: V. Myths of Firearm Injuries and Wound Ballistics: d) Size of temporary cavity determines tissue disruption: .308 Winchester: 2800 fps 7.65 mm Browning: 900 fps -Most temporary cavities are relatively shallow compared to permanent cavity. -Temporary cavity is of very short duration. -Type of tissue significantly affects the wounding potential of temporary cavity: Lung Muscle Liver/Spleen/Brain Bone Fluid filled organs -In general, a faster bullet will produce a larger temporary cavity. Slide53: e) Sensationalization by the Entertainment Industry: Bullets do not possess enough momentum to significantly move a human body. There is often no immediate reaction after being struck in the torso. V. Myths of Firearm Injuries and Wound Ballistics: MacPherson D. Wound Ballistics Review, 1994 Slide54: 4. Clinical Evaluation of G.S.W. – Role of E.P. The Emergency physician: - in ideal position to evaluate and document wounds before they are distorted by surgical intervention. - must resist temptation to make assumptions about findings interpretations are correct in only 47% of cases 1. - do not describe wound as “entrance” or “exit” without indicating physical features of each. - must provide complete documentation of all wounds in 59 patients, only 75% of all actual wounds was documented 2. in 258 GSW’s, accurate anatomical locations were described in only 37% of wounds 1. Busuttil A, et al. Police Surgeon. 1990. 2. Marlowe AL, et al. Proc Am Acad For Sci 1996. Slide55: Clinical Evaluation of G.S.W. – Role of E.P. Exit Entrance Slide56: Clinical Evaluation of G.S.W. – Role of E.P. Entrance Wounds: Divided into 4 general categories according to range of fire: I) Contact ii) Close Range iii) Medium Range iv) Indeterminate When examining entrance wounds, remember: The size of entrance wounds bears no relationship to the caliber of bullet that inflicted it. Slide57: 1. Entrance Wounds – Contact wounds Clinical Evaluation of G.S.W. – Role of E.P. All material (bullet, gases, soot, metal fragments) is driven into the wound Muzzle contusion Slide58: 2. Entrance Wounds – Close Range Clinical Evaluation of G.S.W. – Role of E.P. Distance of less than 6 inches Dispersion of soot (which can be wiped away) Slide59: 3. Entrance Wounds – Intermediate range Clinical Evaluation of G.S.W. – Role of E.P. -Tattooing is pathognomonic Tattooing cannot be wiped away. (soot can) Density of tattooing is dependent on the distance & caliber -Generally found at distances of 60 cm or less. Slide60: 4. Entrance Wounds – distant range Clinical Evaluation of G.S.W. – Role of E.P. No tattooing or deposition of soot Indentation of skin creates Abrasion collar friction b/w bullet and skin (not caused by heat of bullet. palms and soles won’t have abrasion collars. Angle of impact depends on shape Cannot determine distance Slide61: Clinical Evaluation of G.S.W. – Role of E.P. Exit Wounds Skin edges are generally everted Abrasion collars and soot are not usually associated with exit wounds Tattooing is never seen at an exit wound Are NOT always larger than its corresponding entrance wound May not appear directly opposite the entrance wound. Slide62: C. Other Evidence: Clinical Evaluation of G.S.W. – Role of E.P. Opportunity to recognize, preserve, or collect short-lived evidence. Clothing can provide important information. Therefore, place each item in its own separate paper bag. -Every bullet and jacket has its own “fingerprint” Try not to obliterate these marking by removing a bullet with hemostats or pickups Slide63: ”A meticulous evaluation and written description of gunshot wounds by the E.P. can save a very long and tiring process of legal testimony brought on by criminal events” Slide64: The End.