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Taphonomy, Trauma and Skeletal Biomechanics > SAQ assessment > Flashcards

SAQ assessment Flashcards

1
Q

Anisotropic meaning

A

It’s properties depend on direction; Bone is stronger when forces are applied to its longitudinal axis than horizontal; elastically anisotropic.

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2
Q

first level bone structures

A

1.woven bone
2.plexiform bone
3.primary osteonal cortical bone
4.secondary osteonal cortical bone

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3
Q

second level bone structures

A

structures which make up osteons
1. osteoblasts (formers)
2. osteocytes (mature cells)
3. osteoclasts (destroyers)

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4
Q

Two types of bone pattern

A
  1. woven; weak, haphazard organisation
  2. lamellar; strong, regular, parallel
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5
Q

Bone remodelling

A
  • in response to mechanical stress
  • dynamic rather than static loading promotes remodelling
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6
Q

Forces acting on bone

A
  1. tension
  2. compression
  3. torsion
  4. bending
  5. shearing
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7
Q

Affect of forces on femur

A
  • Strongest: compressive longitudinal
  • Weakest: tensile transverse strength
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8
Q

stress definition

A

the measure of the forces acting on a body (load)

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9
Q

load definition

A

the average force per unit area under which forces act

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10
Q

Strain definition

A

Deformation of a deformable body under the application of stress

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11
Q

Young’s modulus

A
  • a measure of the intrinsic stiffness of a material
  • The slope of the stress-strain curve within the elastic region/before the yield point
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12
Q

area under the stress-strain curve

A

a measure of the amount of energy needed to cause material failure; energy absorption/ modulus of toughness

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13
Q

Types of trauma

A
  1. blunt
  2. sharp
  3. ballistic
  4. burning
  5. explosive
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14
Q

displacement fracture

A

when two broken ends of bone no longer meet

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15
Q

Hinge fracture

A

when a break only passes through part of the bone, causing a portion to hinge off but remain attached.

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16
Q

Greenstick fracture

A

no displacement between broken ends - incomplete transverse fracture

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17
Q

comminuted fractures

A

result in multiple pieces

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18
Q

Tension

A
  • Force that pulls on a bone
  • usually directed along the long axis of bone
    -few fracture lines/rare in bone
    -Common in accidents/little forensic relevance
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19
Q

Compression

A

-Forces push down on the bone
-cause fracture lines radiating from point of impact
-most common in skull
-shape may be similar to fracturing instrument
-vertical fracture along long axis of bone
-depressed fracture (skull)
-Torus/buckling fracture; unilateral buckling of cortex at the end of long bones

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20
Q

Torsion

A

-A twisting force when one end of the bone is stationary whilst the other end is twisted
-pedestrian vs car
-Fractures spiral down the long axis of bone (spiral fractures)
-caused by accidents

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21
Q

Bending

A

-force impacts side of bone at right angles to its long axis, compression and tension occur as a result
-Butterfly fracture (apex faces tension, base compression)
-Greenstick fracture; incomplete transverse
-comminuted fracture

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22
Q

Shearing

A

-load is applied at right angles to long axis of bone whilst one end of the bone is fixed in place
-Colles’ fracture (distal radius) from fall onto outstretched arm
-common with accidents or dismemberment

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23
Q

Speed of force/loading rate

A

-Dynamic; sudden stress delivered at a high speed
-Static; stress applied slowly, builds to a point where bone breaks. Usually results in displacement without fracture

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24
Q

Forces causing BFT

A

Compression, bending, shearing

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25
Q

Forces causing SFT

A

Compression or shearing

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26
Q

Forces causing ballistic trauma

A

compressive and bending

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27
Q

delivery of blunt force trauma

A

low-energy impacts resulting from a broad instrument delivered over a relatively large surface area (vehicular accidents most common type)

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28
Q

smaller focus of force

A

less force needed to fracture

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29
Q

stress

A

the force applied to the bone

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30
Q

strain

A

the forces passing through the bone

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31
Q

yield point

A

bent but not broken, will not bounce back (plastic deformation), permanent deformation

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32
Q

Bone failure

A

the fracture of the bone

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33
Q

Young’s modulus of elasticity

A

during the initial stage of loading, elastic deformation, bone is subject to a degree of force with which the bone is able to cope competently

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34
Q

when does plastic deformation take place?

A

after the yield point is reached

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35
Q

sign that both elastic and plastic deformation have occurred

A

bone will fit back together perfectly

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36
Q

slow load application

A

more time for bone to bend, significant deformation is typical of BFT

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37
Q

rapid load application

A

minimal deformation of skeletal tissue, fragments fit together more easily; bone does not progress through the elastic/plastic stages but fails immediately = ballistic or explosive trauma from shearing force

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38
Q

slow loading fracture characteristics

A

tortuous with rougher fracture surfaces
large amounts of peripheral damage
fracture deflects along cement lines, not taking a direct path
fracture is wider and clearly marked

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39
Q

rapid loading fracture characteristics

A

straighter fractures with less peripheral damage
smoother fracture surface
fracture progresses along a single path with minimal deflection, narrower gap

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40
Q

difference in loading type fracture characteristics cause

A

rate dependent change in properties of collagen from brittle to ductile as strain rate increases

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41
Q

Bow fractures

A

plastic deformation = compression bend to bone (juvenile) - result of micro fractures/not reached point of failure

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42
Q

Bone bruise

A

Compression micro fractures = visible radiographically

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43
Q

Torus/buckling fracture

A

unilateral buckling of cortex

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44
Q

greenstick fracture

A

incomplete transverse fracture (juvenile)

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45
Q

Toddlers fracture

A

incomplete spiral or oblique fracture

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46
Q

vertical fracture

A

fracture along long axis = compressive

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47
Q

depressed fracture

A

inward pointing defect = compressive

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48
Q

transverse fracture

A

crosses diaphysis at right angles to long axis

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49
Q

oblique fracture

A

crosses diaphysis on a horizontal

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50
Q

spiral fracture

A

spirals up long axis due to excessive torsion

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51
Q

comminuted fracture

A

break resulting in production of more than 2 pieces

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52
Q

Butterfly fracture

A

wedge of bone separates from fractured ends

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53
Q

segmental fracture

A

three segments

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54
Q

epiphyseal fracture

A

occurs at ends of long bones, can separate epiphysis from diaphyseal metaphysis - can inhibit further growth

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55
Q

bone fails under what force?

A

under tension, stronger under compression

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56
Q

linear skull fracture

A

straight

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57
Q

diastic skull fracture

A

fracture along a suture line

58
Q

Depressed skull fracture

A

hinge/crushing in of skull

59
Q

Stellate skull fracture

A

impact site with radiating fracture lines like the sun and rays

60
Q

First phase skull response to BFT

A

In bending at impact site with concomitant out-bending surrounding the impact site

61
Q

second phase skull response to BFT

A

fracture lines begin at various points on the out-bent surface and progress inward to impact site and outward where they form radiating fracture lines; if force continues, causes the formation of wedge shaped pieces of bones

62
Q

Third phase skull response to BFT

A

If force is sufficient to penetrate vault, concentric fractures occur around the area of impact as tips of the wedge are forced inwards; fractures occur from the outer table to the inner table angling away from the point of impact (hoop fractures)

63
Q

Facial fracturing

A

Blunt forces guided by facial buttresses; breaks occur at set points to dissipate force

64
Q

LeFort 1

A

separation of alveolar part of the maxilla from the rest of the viscerocranium; Results from blow to face from front or side

65
Q

LeFort 2

A

separation of the mid-face from the rest of the viscerocranium; Results from a blow to the anterior mid-face

66
Q

LeFort 3

A

separation of the entire viscerocranium from the neurocranium; Result of a blow to the upper face

67
Q

ring fracture

A

> caused by skull being forced down onto vertebral column; fall onto head from height or onto locked legs or buttocks
begins at posterior occipital and progresses anteriorly

68
Q

order of mandibular fracture

A

body>angle>condyles>symphysis>ascending ramus>coronoid process>temporal bone fracture

69
Q

long bone BFT

A

> usually delivers compressive and bending forces to long bones
results in complete, simple fractures without fracture lines; can be comminuted with significant force

70
Q

Rib fracture

A
  • Can break anywhere along body but prone to break at anterior end
  • Anterior or lateral blows
  • Break at right angles to long axis when viewed externally
    When viewed superiorly or inferiorly they are observed to break from outside to inside
71
Q

Vertebrae fracture

A

Simple fractures of transverse or spinous processes

72
Q

Pelvis fracture

A
  • Ischiopubic ramii
    Iliac crest
73
Q

Scapula fracture

A
  • Separation of glenoid
    Fracture of coracoid
74
Q

sequencing blunt force trauma

A

> intersection of fractures
energy dissipates between fractures, not enough energy present to jump fractures/sutures

75
Q

SFT wound type

A

puncture; cone shaped focus perpendicular to bone surface
incision; force applied over long, narrow surface area
cleft; dynamic force from a long, sharp edged implement applied perpendicular to bone surface

76
Q

SFT bone damage

A

> fracture lines (rare)
hinge fractures = green bone effct
wastage/separation

77
Q

primary characteristics of SFT

A

> cross-sectional shape
width
depth
length
striations

78
Q

secondary characteristics of SFT

A

> fracture lines
hinge fractures
wastage
direction of kerf (cut) can sometimes be discerned

79
Q

Knife kerf formation

A

> straight even edges, breadth remains consistent over length of kerf.
little debris found in walls and floor
extremities of kerf are thinner and pointed
if angle differs from 90 degrees, one side of kerf will be raised and fractured (bone flakes) with the other remaining smooth.
Little/no lateral compression

80
Q

Hatchet kerf formation

A

> width of kerf same for entire length
kerf irregular compared to knife due to blunt mechanism
smooth walls and floor = sharp edge
edges uneven with significant bone flaking and fracturing found adjacent
significant lateral compression and destruction

81
Q

3 categories of SFT tool

A

> stabbing
cutting
chopping

82
Q

3 types of marks caused by saws to bone

A
  1. superficial false start kerfs: initial low pressure draw across bone
  2. False start kerfs: shallow incomplete saw kerf; allows for estimation of max. width of blade
    3.Sectioned bone cuts: deep kerfs
83
Q

SFT entry and exit wounds

A

entry wound larger than exit

84
Q

bullet trajectory/impact perpendicular to target

A

circular outline

85
Q

bullet trajectory/impact not perpendicular to target

A

oblique outline

86
Q

bevelling (ballistic trauma)

A

> when projectiles strikes bone, it deforms to a variable degree
causes exit defect to be larger than entry
defect adopts funnel shape = bevelling

87
Q

Inward bevelling

A

> observed at entry site
external defect smaller than internal defect
inward bevelling seen on internal surface of entry point

88
Q

outward bevelling

A

> observed at site of exit
internal defect smaller than external defect

89
Q

Reverse bevelling

A

> characterised by bevelling on the external surface of an entry defect in addition to bevelling on the internal surface

90
Q

Ballistic defect shapes

A
  1. round
  2. oval
  3. keyhole
  4. irregular
91
Q

round ballistic defect

A

> angle of trajectory and bullet axis are perpendicular to bone surface
More likely in entry rather than exit wounds
jacketing may result in round entry and exit wound

92
Q

oval ballistic defect

A

> occurs when; angle of trajectory is not perpendicular to bone surface or bullet is tumbling when it strikes = <90 degree angle between bone and bullet.
more common in entry wounds

93
Q

Keyhole ballistic defects

A

> usually caused by bullet grazing bone/entering at an angle
occasionally viewed in exit wounds
commonly observed in cranial vault
originates from any bullet type

94
Q

Irregular ballistic defects

A

> no uniform outline
result of bone shattering = high velocity projectiles
more characteristic of exit wounds but can be observed at entry where bullet has been obstructed

95
Q

Ballistic fracture lines

A

> radiating: originate from site of impact
concentric: encircling entry point; occurs in internal cortex then external

96
Q

BFT vs Ballistic

A

> BFT = inward bevelling concentric fractures due to tensile failure
Ballistic = externally bevelled concentric fracture due to tension on intracranial surface due to elevated pressure

97
Q

sequencing ballistic trauma

A

> distinguish entry from exit
distinguish radiating from concentric fracture
identify radial fracture intersection

98
Q

heat flux

A

> the rate of energy transfer through a surface per unit time, measure in watts or kilowatts
dictates what materials become involved in a fire

99
Q

Heat Release Rate (HRR)

A

> the rate at which a fire will release energy, measure in kilowatts or mega watts

100
Q

Heat of combustion

A

> total energy released as heat when a material undergoes complete combustion = exothermic reaction

101
Q

Heat transfer

A

> the process by which heat energy moves from one object to another via radiation, conduction or convection

102
Q

burn progression on non-combustible floor for duration of fire

A

Body will burn more severely on the surface that is exposed to the fire
showing less damage on the side in contact with the non-combustible floor

103
Q

burn progression on top of burning items

A

The side of the body in contact with the burning items will burn first, proceeding up around the body.

104
Q

burn progression on combustible floor that collapses during fire

A

The floor, if combustible, will act as fuel and burn the side of the body in contact with it.
If the floor collapses, remains could be deposited over a wide area = fragmentation

105
Q

burn progression In suspension on metal framework

A

The car seat or mattress may initially shield the body.
If the fire then continues to burn long enough, the fragmented remains may fall through the framework and scatter.

106
Q

burn progression Exposed on all sides

A

The body will burn on all sides, and burning will progress in a relatively predictable way.

107
Q

Stages of the burning process

A
  1. Dehydration; 100-600c = black cortex
  2. Decomposition; removal of organic components = 300-800c, grey colour indicated leeching of organics
  3. Inversion; 500-1100c, Removal of carbonates = white colour of bone
  4. Fusion; 700-1200c, warping of crystals
108
Q

Colour change in burned bone

A
  1. unaltered
  2. Heat line = white line
  3. Heat border = brown - white band
  4. Charred = black
  5. Calcined = grey-white
109
Q

brown colour change association

A

haemoglobin or soil discolouration

110
Q

Black colour change association

A

carbonisation of burned bone (300c)

111
Q

Grey/blue colour change association

A

pyrolysis of organic components of bone (600c)

112
Q

White colour change association

A

final end stage of calcination (800c)

113
Q

Green/yellow/pink/red colour change association

A

presence of copper, bronze, zinc in surrounding environment

114
Q

Heat induced fractures

A
  1. Patina
  2. longitudinal
  3. Curvilinear
  4. transverse
115
Q

Patina fracture

A

> observed on surface of flat bones + long bones
fine cracks, do not penetrate marrow cavity

116
Q

Longitudinal fractures (burning)

A

> follow long axis of bone
may penetrate marrow cavity
follow orientation of collagen fibres

117
Q

curvilinear fractures

A

> can exhibit oblique orientation
circumscribe long bone shaft

118
Q

Transverse fractures (burning)

A

> perpendicular to shaft
delamination fracture = peeling or flaking of bone layers, separates cortex from trabeculae

119
Q

primary explosive injuries

A

> Causes by pressurised shock wave moving through body
characterized by the absence of external injuries
targets gas containing organs
internal injuries are frequently unrecognized and underestimated

120
Q

Secondary explosive injury

A

> caused by the propulsion of objects into the individual
can cause penetrating trauma and hemmorrhage.
anti-personnel bombs

121
Q

Tertiary explosive injuries

A

> when a person themselves is thrown against other objects
blunt force trauma = fractures

122
Q

Quaternary explosive injuries

A

> includes burns, crushing and respiratory injuries

123
Q

Torture definition

A

> any act by which severe pain and suffering is intentionally inflicted on a person, when such pain and suffering is inflicted by or at the instigation of a public official or someone acting in an official capacity

124
Q

Evidence to support torture

A

1.comparing pattern of injuries to documented cases of torture
2.Timing of injuries (sustained over a prolonged period)
3.pathological findings consistent with detainment (untreated disease/injury)
4. Corroboration with other physical findings

125
Q

istanbul protocol

A

manual on effective investigation and documentation of torture and other cruel treatment or punishment.

126
Q

Istanbul protocol recommendations (torture)

A

> experts must avoid speculation
Must take into account the variability of lesions depending on the victim and the severity of the lesions themselves.
all lesions must be recorded, whole body observed in detail
Consider region specific methods

127
Q

inflicted injury types

A

> sternal fractures
hands and feet
parry fracture = forearm, defensive

128
Q

Accidental injury types

A

> colles fracture = distal radius
clavicle
humerus

129
Q

5 types of abuse

A
  1. physical
  2. sexual
  3. neglect and negligent treatment
  4. emotional
  5. exploitation
130
Q

what to look for in abuse cases:

A
  1. injuries which are unlikely to be accidental
    2.injuries in different stages of healing
    3.indicators of untreated injuries
    4.injuries which do not fit the story given
131
Q

Oral injuries = abuse

A

> torn labial frenum
fractured/chipped teeth
bruising to tongue, cheeks
fractured mandible/maxilla

132
Q

soft tissue abuse indicators

A

> bruising
bite marks
burns
scalds
ligature marks
pressure sores

133
Q

kwashiorkor

A

severe lack of protein but sufficient calorie intake.
>oedema, irritability, ulcerating dermatose, enlarged liver + hair discolouration

134
Q

marasmus

A

> lack of protein and calories
emaciated, dehydrated, prone to infection and circulatory disorders

135
Q

Harris lines

A

> reaction to stress (neglect)
transverse sclerotic layers in the metaphysis indicating times of reduced growth
ribs and long bones especially tibia and distal femur.

136
Q

Enamel hypoplasias

A

> poor thin enamel, laid down in lines
linked to periods of ill-health and infection or starvation

137
Q

bucket handle fractures

A

> metaphyseal fractures
caused by twisting or wrenching of extremities causing the metaphysis to be pulled and fractured

138
Q

Heat related fracture characteristics

A

> occur in early stages of burning
radiate from charred black areas into buff coloured bone
will never radiate into unburnt bone
well-defined, sharp margins

139
Q

Pre-existing fracture characteristics (burning)

A

> may extend into unburned bone
will have eroded, deformed margins due to thermal exposure
tool marks from blunt and sharp force trauma will still be visible
bevelling from ballistic trauma is retained

140
Q
A

Taphonomy, Trauma and Skeletal Biomechanics (2 decks)

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