SAQ assessment Flashcards
(140 cards)
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.
2
Q
first level bone structures
A
1.woven bone
2.plexiform bone
3.primary osteonal cortical bone
4.secondary osteonal cortical bone
3
Q
second level bone structures
A
structures which make up osteons
1. osteoblasts (formers)
2. osteocytes (mature cells)
3. osteoclasts (destroyers)
4
Q
Two types of bone pattern
A
- woven; weak, haphazard organisation
- lamellar; strong, regular, parallel
5
Q
Bone remodelling
A
- in response to mechanical stress
- dynamic rather than static loading promotes remodelling
6
Q
Forces acting on bone
A
- tension
- compression
- torsion
- bending
- shearing
7
Q
Affect of forces on femur
A
- Strongest: compressive longitudinal
- Weakest: tensile transverse strength
8
Q
stress definition
A
the measure of the forces acting on a body (load)
9
Q
load definition
A
the average force per unit area under which forces act
10
Q
Strain definition
A
Deformation of a deformable body under the application of stress
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
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
13
Q
Types of trauma
A
- blunt
- sharp
- ballistic
- burning
- explosive
14
Q
displacement fracture
A
when two broken ends of bone no longer meet
15
Q
Hinge fracture
A
when a break only passes through part of the bone, causing a portion to hinge off but remain attached.
16
Q
Greenstick fracture
A
no displacement between broken ends - incomplete transverse fracture
17
Q
comminuted fractures
A
result in multiple pieces
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
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
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
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
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
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
24
Q
Forces causing BFT
A
Compression, bending, shearing
25
Forces causing SFT
Compression or shearing
26
Forces causing ballistic trauma
compressive and bending
27
delivery of blunt force trauma
low-energy impacts resulting from a broad instrument delivered over a relatively large surface area (vehicular accidents most common type)
28
smaller focus of force
less force needed to fracture
29
stress
the force applied to the bone
30
strain
the forces passing through the bone
31
yield point
bent but not broken, will not bounce back (plastic deformation), permanent deformation
32
Bone failure
the fracture of the bone
33
Young's modulus of elasticity
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
34
when does plastic deformation take place?
after the yield point is reached
35
sign that both elastic and plastic deformation have occurred
bone will fit back together perfectly
36
slow load application
more time for bone to bend, significant deformation is typical of BFT
37
rapid load application
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
38
slow loading fracture characteristics
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
39
rapid loading fracture characteristics
straighter fractures with less peripheral damage
smoother fracture surface
fracture progresses along a single path with minimal deflection, narrower gap
40
difference in loading type fracture characteristics cause
rate dependent change in properties of collagen from brittle to ductile as strain rate increases
41
Bow fractures
plastic deformation = compression bend to bone (juvenile) - result of micro fractures/not reached point of failure
42
Bone bruise
Compression micro fractures = visible radiographically
43
Torus/buckling fracture
unilateral buckling of cortex
44
greenstick fracture
incomplete transverse fracture (juvenile)
45
Toddlers fracture
incomplete spiral or oblique fracture
46
vertical fracture
fracture along long axis = compressive
47
depressed fracture
inward pointing defect = compressive
48
transverse fracture
crosses diaphysis at right angles to long axis
49
oblique fracture
crosses diaphysis on a horizontal
50
spiral fracture
spirals up long axis due to excessive torsion
51
comminuted fracture
break resulting in production of more than 2 pieces
52
Butterfly fracture
wedge of bone separates from fractured ends
53
segmental fracture
three segments
54
epiphyseal fracture
occurs at ends of long bones, can separate epiphysis from diaphyseal metaphysis - can inhibit further growth
55
bone fails under what force?
under tension, stronger under compression
56
linear skull fracture
straight
57
diastic skull fracture
fracture along a suture line
58
Depressed skull fracture
hinge/crushing in of skull
59
Stellate skull fracture
impact site with radiating fracture lines like the sun and rays
60
First phase skull response to BFT
In bending at impact site with concomitant out-bending surrounding the impact site
61
second phase skull response to BFT
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
Third phase skull response to BFT
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
Facial fracturing
Blunt forces guided by facial buttresses; breaks occur at set points to dissipate force
64
LeFort 1
separation of alveolar part of the maxilla from the rest of the viscerocranium; Results from blow to face from front or side
65
LeFort 2
separation of the mid-face from the rest of the viscerocranium; Results from a blow to the anterior mid-face
66
LeFort 3
separation of the entire viscerocranium from the neurocranium; Result of a blow to the upper face
67
ring fracture
> 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
order of mandibular fracture
body>angle>condyles>symphysis>ascending ramus>coronoid process>temporal bone fracture
69
long bone BFT
>usually delivers compressive and bending forces to long bones
>results in complete, simple fractures without fracture lines; can be comminuted with significant force
70
Rib fracture
* 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
Vertebrae fracture
Simple fractures of transverse or spinous processes
72
Pelvis fracture
* Ischiopubic ramii
Iliac crest
73
Scapula fracture
* Separation of glenoid
Fracture of coracoid
74
sequencing blunt force trauma
>intersection of fractures
>energy dissipates between fractures, not enough energy present to jump fractures/sutures
75
SFT wound type
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
SFT bone damage
>fracture lines (rare)
>hinge fractures = green bone effct
>wastage/separation
77
primary characteristics of SFT
>cross-sectional shape
>width
>depth
>length
>striations
78
secondary characteristics of SFT
>fracture lines
>hinge fractures
>wastage
>direction of kerf (cut) can sometimes be discerned
79
Knife kerf formation
>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
Hatchet kerf formation
>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
3 categories of SFT tool
>stabbing
>cutting
>chopping
82
3 types of marks caused by saws to bone
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
SFT entry and exit wounds
entry wound larger than exit
84
bullet trajectory/impact perpendicular to target
circular outline
85
bullet trajectory/impact not perpendicular to target
oblique outline
86
bevelling (ballistic trauma)
>when projectiles strikes bone, it deforms to a variable degree
>causes exit defect to be larger than entry
>defect adopts funnel shape = bevelling
87
Inward bevelling
>observed at entry site
>external defect smaller than internal defect
>inward bevelling seen on internal surface of entry point
88
outward bevelling
>observed at site of exit
>internal defect smaller than external defect
89
Reverse bevelling
>characterised by bevelling on the external surface of an entry defect in addition to bevelling on the internal surface
90
Ballistic defect shapes
1. round
2. oval
3. keyhole
4. irregular
91
round ballistic defect
>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
oval ballistic defect
>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
Keyhole ballistic defects
>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
Irregular ballistic defects
>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
Ballistic fracture lines
>radiating: originate from site of impact
>concentric: encircling entry point; occurs in internal cortex then external
96
BFT vs Ballistic
>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
sequencing ballistic trauma
>distinguish entry from exit
>distinguish radiating from concentric fracture
>identify radial fracture intersection
98
heat flux
>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
Heat Release Rate (HRR)
>the rate at which a fire will release energy, measure in kilowatts or mega watts
100
Heat of combustion
>total energy released as heat when a material undergoes complete combustion = exothermic reaction
101
Heat transfer
>the process by which heat energy moves from one object to another via radiation, conduction or convection
102
burn progression on non-combustible floor for duration of fire
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
burn progression on top of burning items
The side of the body in contact with the burning items will burn first, proceeding up around the body.
104
burn progression on combustible floor that collapses during fire
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
burn progression In suspension on metal framework
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
burn progression Exposed on all sides
The body will burn on all sides, and burning will progress in a relatively predictable way.
107
Stages of the burning process
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
Colour change in burned bone
1. unaltered
2. Heat line = white line
3. Heat border = brown - white band
4. Charred = black
5. Calcined = grey-white
109
brown colour change association
haemoglobin or soil discolouration
110
Black colour change association
carbonisation of burned bone (300c)
111
Grey/blue colour change association
pyrolysis of organic components of bone (600c)
112
White colour change association
final end stage of calcination (800c)
113
Green/yellow/pink/red colour change association
presence of copper, bronze, zinc in surrounding environment
114
Heat induced fractures
1. Patina
2. longitudinal
3. Curvilinear
4. transverse
115
Patina fracture
>observed on surface of flat bones + long bones
>fine cracks, do not penetrate marrow cavity
116
Longitudinal fractures (burning)
>follow long axis of bone
>may penetrate marrow cavity
>follow orientation of collagen fibres
117
curvilinear fractures
>can exhibit oblique orientation
>circumscribe long bone shaft
118
Transverse fractures (burning)
>perpendicular to shaft
>delamination fracture = peeling or flaking of bone layers, separates cortex from trabeculae
119
primary explosive injuries
>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
Secondary explosive injury
>caused by the propulsion of objects into the individual
>can cause penetrating trauma and hemmorrhage.
>anti-personnel bombs
121
Tertiary explosive injuries
>when a person themselves is thrown against other objects
>blunt force trauma = fractures
122
Quaternary explosive injuries
>includes burns, crushing and respiratory injuries
123
Torture definition
>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
Evidence to support torture
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
istanbul protocol
manual on effective investigation and documentation of torture and other cruel treatment or punishment.
126
Istanbul protocol recommendations (torture)
>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
inflicted injury types
>sternal fractures
>hands and feet
>parry fracture = forearm, defensive
128
Accidental injury types
>colles fracture = distal radius
>clavicle
>humerus
129
5 types of abuse
1. physical
2. sexual
3. neglect and negligent treatment
4. emotional
5. exploitation
130
what to look for in abuse cases:
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
Oral injuries = abuse
>torn labial frenum
>fractured/chipped teeth
>bruising to tongue, cheeks
>fractured mandible/maxilla
132
soft tissue abuse indicators
>bruising
>bite marks
>burns
>scalds
>ligature marks
>pressure sores
133
kwashiorkor
severe lack of protein but sufficient calorie intake.
>oedema, irritability, ulcerating dermatose, enlarged liver + hair discolouration
134
marasmus
>lack of protein and calories
>emaciated, dehydrated, prone to infection and circulatory disorders
135
Harris lines
>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
Enamel hypoplasias
>poor thin enamel, laid down in lines
>linked to periods of ill-health and infection or starvation
137
bucket handle fractures
>metaphyseal fractures
>caused by twisting or wrenching of extremities causing the metaphysis to be pulled and fractured
138
Heat related fracture characteristics
>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
Pre-existing fracture characteristics (burning)
>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
