ANT3250 Week 5 notes- Trauma (blunt, sharp force and GSW) and burned bones
ANT3250 Week 5 notes- Trauma (blunt, sharp force and GSW) and burned bones ANT3520
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This 10 page Class Notes was uploaded by Janaki Padmakumar on Saturday July 30, 2016. The Class Notes belongs to ANT3520 at University of Florida taught by Amanda Friend in Summer 2016. Since its upload, it has received 8 views.
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Date Created: 07/30/16
Week 5 notes L 19 Trauma Trauma- an injury or wound to living tissue caused by an extrinsic agent; a force acting upon the body Fracture (when there is breakage in the bone) causes: Stress- repetitive loading and stressing on the bone Pathology- fracturing of bone already weakened by disease Trauma o Acute and quick event, solely caused by sudden injury o Bone previously free from disease o Everything acting on bone will also affect surrounding soft tissue Living bone tissue Two parts Collage and other proteins forming organic compound Hydroxyapatite Allows a certain amount of rigidity and flexibility Fracture mechanics Fractures caused by different mechanisms can look similar; same mechanism for fracture can appear different Factors: o Magnitude, duration, and direction of force o Elasticity, density and strength of bone Stress- force applied to a given area of bone (depends on scope of force) Strain- deformation (relative to original size and shape of the bone) o Deformation curve (3phases) Elastic- bone deforms but returns to its original shape Plastic- deformation occurs but does not return to original shape; does not break Failure- bone fracture occurs *as stress and strain increases, likelihood of failure increases Forces resulting in trauma (acute injury to bone) Tension- usually in joints, like when arm is pulled Compression Bending Shear (sliding; happens when one end of the bone is mobilized) Torsion (twisting, forms a spiral fracture) Bone always breaks first with tension Compression pushes inward on one surface, thus causing tension on the other surface; tension side will break first. Definitions Ante- before; antemortem, used for personal ID based on prior records Occurs during lifetime Signs of healing or infection present at time of death Often edges of bone appear blunted or smooth Can have bone callouses or improper alignment Peri- at/around Post- after (postmortem damage, not trauma) Healing phases Reactive o Fracture and inflammation (hematoma0 o Granulation tissue formation (bony bridge); osteoplasts consume dead bone, relay new bone Reparative o Callous formation (woven) o Lamellar bone (concentric osteon rings) deposition Remodeling o Original bone contour; osteoblast/osteoclast homeostasis Fracture repair timing Hematomas- few hours Callous forms in about 21 days Remodeling takes 4-6 weeks and continues along lifetime Complete remodeling- 3 to 5 years Healing length varies; dependent on: Fracture severity Site of fracture Extent of fracture immobilization Age and health If a bone is completely healed, you can't tell when it was broken Imperfect repair Angulation- limb can be distended or shorter May or may not affect limb function Pseudoarthrosis- extreme disjunction of a fracture; forms a "false joint" Common fractures Boxer's fracture- fracture to the head of the 5th metacarpal Forearm fractures (names not always used in forensic lit or medical community; displacement of bone and ligament involvement can't be observed by FA) o Colles'- foosh (falling on outstretched hand);Dorsal angulation of distal radial fragment, if opposite, then reverse colles' o Parry- break through ulnar diaphysis; typically result of defense, force absorbed by ulna o Monteggia- foosh; proximal ulnar shaft diaphysis fracture; radial head gets displaced o Galeazzi - foosh- break through radius and ulna is displaced Pars fracture- to vertebral arch of lowest (usually 5th) lumbar vertebra o Can also be a congenital defect o Pars interarticularsis- common in gymnasts and football players; repetitive hyperextension cause Spondylolysis Spondylolithesis (disc slippage, requires intervention) Weber fracture- distal tibia and fibula fracture o Eversion and inversion with rotation of the foot Perimortem trauma Occurring at or around time of death Bone is still "fresh" Shows no evidence of healing Not caused by taphonomic processes Three types Blunt force Sharp force Ballistic (includes projectiles, not just gunshots) Same implement can cause blunt and sharp force trauma (like hammer blunt v sharp end used) Perimortem characteristics Lack of osseous response Uniform coloration of broken and intact bone Presence of depressed fractures, concentric fractures, radiating fractures, and/or stellate fractures Adherent bone spurs or splintering Beveled/oblique fracture margins Postmortem damage Not trauma Damage to body occurring after death May occur anytime during the postmortem interval Charas of postmortem: o Smaller, more numerous fragments since organic component is gone o Right angled/squared fracture margins o Absence of identifiable fracture patterns (depressed/radiating) o Concentric and/or stellate fractures o Absence of adherent bone spurs or splintering o Coloration differences between fracture margins and adjacent intact bone L20 Blunt force trauma Caused by relatively low velocity force distributed over a relatively large surface area Blunt object striking body- acceleration trauma (bat hitting arm, rock hitting skull) Moving body striking blunt object or the ground- deceleration trauma (car accidents, falls, plane crashes) BFT to the cranium Linear fractures: caused by low velocity, high mass o Can Emanate from point of impact and radiate outward (radiating, stellate(starbust)) o Can circumscribe point of impact as the result of outbending (concentric) o Fractures tend toward path of least resistance (sometimes diastatic); happen at thinnest part of skull and ends at suture (thicker part) o 70-80% skull fractures caused by high mass low velocity impacts Le fort: o Midface fracture o Separation of maxilla and/or zygomatics from the cranium o Lower face blow to separate maxilla (La fort I) o Result of anterior blow to midface (II) o La fort III goes through eye orbits o Centrally focused blow Plastic deformation o Permanent deformation of bone o Fracture margins don’t line up o Can be seen in relatively elastic bones, particularly in kids Depressed fractures (higher velocity) o High velocity, small mass o Results in crushed outer table o Localized areas of detached bone that are pushed inward Pattern defects When BFT defect has impressions of objects that caused the impact Not commonly found in bone Can never conclusively correlate single weapon to skeletal defect with 100% certainty Can talk about approximations of implement used, like rounded end, curved edge, length etc Sequence of BFT Later fractures will terminate into earlier ones Earlier fracture margins can be knapped If there are multiple bows, can be impossible to determine exact sequence Long bone fractures BFT causes bending and compression fractures Transverse, oblique, spiral, segmental, comminuted and impact fractures Usually complete fractures All the way through bone Incomplete=greenstick fractures; common in kids since bones are more elastic bc cartilaginous Fracture types Compound/open o Sticks out through skin o Can be segmental or comminuted (or another type described) Transverse o Right angle to bone's long axis o Displaced/nondisplaced Oblique o Oblique fracture of the bone shaft producing a curved or sloped pattern Spiral fracture o Oblique fracture occurring around the shaft o Torque applied to long axis Segmental fractures o Results in three fragments o Dependent on joint type, age, health o Butterfly fracture Segmental fracture Center segment is a triangle Indicates directionality of force; triangle forms on compression side Comminuted o Several complex fractures with many bone fragments o Open or closed Impacted/buckle o Compression of two fragments on the same bone o Common in falls, car accidents Greenstick o Incomplete fracture o Bone bends but doesn’t break o Common in children L21 Sharp force trauma Essentially blunt force trauma distributed over a small surface area Main defect in one is produced by physical interruption of bone by foreign object- item goes through the bone Can also create tension/compression fractures of BFT Can produce: Incisions Puncture/stabbing wounds Chopping/hacking injuries Indicators of perimortem trauma, accidents, defensive wounds Incised wounds: Length is greater than depth V shaped in cross section One side is lifted relative to other Varies with blade type, applied force and weapon track as it moves through tissue o Same weapon can produce different cuts Stab/puncture wounds Depth> length Caused by sharp ended instrument being thrust into tissue Can provide info about depth, width and cross sectional shape of instrument Can also produce radiating fractures Chopping/hacking wounds Instruments like axes or machetes with load applied perpendicular to sharp edge Crushing component Can leave striations that record irregularities along blade length o Can compare to object thought to be the murder weapon o Damage done depends on force applied SFT effects: Radiating fractures- terminate in sutures and other fractures Hinge fractures- occurs in hydrated tissue, fragments bent inward instead of breaking away Wastage- chopping motions; fragments of bone can fly off like wood chips when chopping wood Blade size Deep, small wounds= puncture tools Assess how accessible wound area was- harder accessibility correlates to longer blade Number of SFT Should be able to count number of wounds, but: o Single event can cause multiple wounds o Can be flesh wounds that don’t appear on bone o Chopping/hacking can destroy prior marks Dismemberment saw marks Kerf: the walls and floors of cut marks Can be used to determine saw type and characteristics Usually involves knives and saws Crosscut saw, rip saw, teeth per inch, kerf width, etc. Breakaway spurs Projection of uncut bone Found at terminal ends of cut after the force of the saw breaks remaining intact bone Accompanied by a notch on the opposite piece False starts Kerf cut that doesn’t completely sever bone Provides information about the saw L22 Ballistics and GSW Ballistics- science of projectiles in flight Internal ballistics- travel within gun barrel External ballistics- travel from gun muzzle to target Terminal ballistics- path through target Ammunition Cartridge/round o Bullet o Caliber o Casing Lead bullets No jacket Primary use in revolvers Flattens or breaks apart within target Semi-jacketed bullets Nose of bullet has exposed lead Not completely covered by jacket Expands when target is struck Prevents fragmentation Easier to match intact bullets than fragmented Full metal jacket Jacket covers all but base of bullet Prevents deformation Meant to pierce armor- doesn’t fragment so that it can do damage Primarily military rounds Shells Shotgun ammo Cartridge: o Single large projectile called slug o Many spherical pellets (shot) made from lead or steel Shotgun measured by gauge (max weight of lead ball that fits in the barrel) What can a GSW tell you Estimate size of bullet (caliber) Trajectory- the path into or through the body Velocity Determining caliber May be able to group likelihood of projectile caliber from measuring entrance wound Depends on range, projectile type and design Expansion of bullet is an issue Trajectory- path projectile takes through body Indicates something about positional relationship between shooter and vic Velocity- discernible in broad terms Low velocity/low energy High velocity/high energy Generally higher velocity causes more damage Wound types Penetrating o Bullet enters body/organ/structure but does not exit o Entrance wound only Perforating o Bullet enters and exits the body/organ/structure o Entrance and exit wounds GSW- entrance and exit wounds Entrance o Internal beveling (inward curvature) o Hertzian cone produced; bullet keeps going through to produce larger exit wound Exit o External beveling o Always larger than entrance Associated fractures o Radiating fracture from GSW o Concentric fracture produced mm or in away from GSW Keyhole entrance o Caused by acute angle of trajectory in relation to the bone o See internal and external beveling along margins of a single defect Shotgun wounds Intermediate targets o Possibility that bullet could be passed through another target o Alter appearance of projectile defect and confound data interpretation o Considered when defect is irregular or projectile behaved oddly GSW and x-rays X-ray all suspected GSW to look for metal in the bone L23 Burned bone Pugilistic pose (body curls up when muscles and tendons contract after heat exposure) Reasons for burning bodies Make remains less identifiable Cover up crime Burn patterns-palms last to burn; dorsal side with small amount of tissue burns first, ventral has more tissue to burn through before bone is impacted *tissue shielding* prevents certain parts of the body from burning; greater amount of soft tissue means more time taken to burn 3 stages of change in burned bone First o 100-5 or600 degrees C o Removal of loosely attached water Second o 600-800 o Collagen lost and bone weight reduces Third o Greater than 800 o Rest of organic material combusts and hydroxyapatite crystals enlarge Color changes in burned bone (least to most burnt) Yellow- light brown Black (charred) Blue -grey White (calcined) Shape changes Shrinkage between 6-25% of actual size; one warping also occurs, cracking and curvature Fracturing: Longitudinal (rarely breaks like this normally) Transverse o Curved transverse (thumbnails); don’t go very deep into cortical bone Patina (turtleshell or dry riverbed pattern) Information in burned bone State of the remain o Fleshed bone, dry or defleshed bone based on burn patterns determinations Position of body- if one portion was closer to the fire, burned more severely o Use of accelerant- increase speed or heat of fire to burn bodies faster Biological profile Trauma Individualized characteristics Reconstruction of remains Cement to glue pieces together unless bone itself is very fragile Dental wax, modeling clay Cremains analysis- done on very small pieces of bone; could be because of ethical, errors made or family concerns Steps to a cremains analysis Document container, labels, remains Weighing remains Separations by size Radiographs Visual inspection Photograph everything Lines of evidence for identity of remains Bone and tooth fragments Cremation weight Related to Sex Age Stature Body weight o Do remains fall clearly within range of variation for males? Females? Or in area of overlap? Cremation artifacts (metal tags to ID body, pacemaker, surgical screws) o Vascular clips o Pacemaker components o Orthopedic hardware o Dental: o Implants o Bridges, crowns o Dentures o Restorations o Mortuary o Embalming; embalming needles o Jewelry fragments o Clothing o Items on body at time of cremation o Misc: o Slag o Refractory brick and concrete fragments o Non-specific metal fragments Chemical analysis (XRF to test for human bone composition) o Done to distinguish between cremated bone and other material o Life history of an individual (teeth can be tested for dietary indicators) o Traumatic event during life o Post depositional changes (residual changes) DNA analysis in cremated remains Not everyone in databank Not substantiated in scientific lit Bone exposed to temperatures below commercial cremation temp don’t yield DNA
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