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Blunt Force Injury Flashcards

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1
Q

What is the definition of trauma

A

Bodily harm due to transfer of energy from whatever source to the tissues
+/- structural damage and/or physiological effects

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2
Q

What is meant by structural damage in trauma

A

Damage to the underlying body structure

Includes bruising, laceration and breaking the underlying bone

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3
Q

What is meant by physiological effects in trauma

A

Usually a neurological reaction to the trauma such as damaging or effecting the nerves below
Can occur without any outward injury
E.g. Blunt force to the neck can cause reflex cardiac arrest by stimulating the nerves

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4
Q

What is the medical definition of a wound

A

Disruption in the continuity of the tissues produced by external mechanical force

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5
Q

What is the legal definition of a wound

A

Breach of the full thickness of the skin or lining of the lip
Less useful than medical definition
Excludes bruising, abrasions and closed fractures

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6
Q

Which types of blunt force trauma are not legally considered wounds

A

Bruises
Abrasions
Fractures (unless open)

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7
Q

Does every blunt force impact cause an injury

A

No

A punch can lead to bruising etc but can also have little/no effect on the tissue

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8
Q

What is the definition of an injury

A

Synonymous with wound but a broader term and therefore more useful
Also includes damage caused by heat, cold, electricity, chemicals and radiation

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9
Q

What is the definition of lesion

A

Used to describe any area of injury, disease (e.g. wart or tumour) or local degeneration in a tissue causing a change in its structure or function
May be used by pathologist if they are not sure the exact nature of the area

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10
Q

How does electricity cause a burn

A

Electricity flows through the body and damages the tissue and can cause injury

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11
Q

How can a ‘blast’ cause an injury

A

Changes in atmospheric pressure cause tissue damage

Particularly to the lungs and internally

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12
Q

What are the 3 types of mechanical force injuries

A

Blunt force trauma
Sharp force trauma
Explosive/firearms force

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13
Q

List the 7 main ways that mechanical force can damage tissue

A

Impact
Angulation - tissue is bent
Compression
Traction - tissues are pulled apart
Torsion - twisting force
Shearing -sliding one layer of tissue over another (chinese burn)
Acceleration/Deceleration- seen in falls from height or RTA

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14
Q

How does degree of force affect injury

A

Greater the force the greater the likelihood of injury

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15
Q

How does tissue area affect injury

A

Energy will be spread out over the area making contact

If larger area the tissues can disperse the energy and leads to less injury

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16
Q

How do you calculate kinetic energy

A

half the mass of the object multiplied by the speed of the object squared
Higher mass and higher speed = greater force

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17
Q

How does duration of force affect injury

A

Quicker duration gives greater sudden energy

Slow push of knife less likely to penetrate than quick stab

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18
Q

What physical factors affect a forces’ ability to cause injury

A 
Degree of force applied 
Area of application of force 
Duration 
Direction - glancing vs direct blows 
Tissue properties - viscosity, plasticity and elasticity
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19
Q

What is meant by tissue viscosity

A

How fluid the tissue is

Protective factor

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20
Q

What is meant by tissue plasticity

A

How the tissue copes with change (how its bends etc)

Protective factor

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21
Q

What is meant by tissue elasticity

A

How quickly the tissue goes back to its natural state - how springy it is
Protective factor

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22
Q

How does direction of force affect injury

A

Direct, resting impact will deliver all of its energy and therefore cause greater injury
Glancing blows do not give up all energy so injure less

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23
Q

How do you calculate energy of a vehicle crash

A

mph2 x 0.034

Divided by stopping distance (use consistent units)

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24
Q

Why is stopping distance so important in a vehicle crash

A

If the car is able to slow down over a large distance then there is less energy on impact - less injury
If you hit an object at high speed the car stops immediately and a lot of energy is transferred - occupants and car absorb a lot of energy = more injury

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25
What is the benefit of a large crumple zone in your car
Greater the crumple zone in the car the more energy the vehicle can absorb and the less the occupants do Reduces injury
26
What biological factors can influence injury
Mobility of body part Anticipation and coordination The biomechanical properties of tissues
27
How does mobility of the body part affect injury
If the body part impacted is able to move with the direction of force it absorbs less energy directly and therefore is less injured e. g. moving with a punch is less likely to injure than staying still e. g. more likely to injure a standing/stationary leg than swinging/moving leg
28
How does anticipation and coordination affect injury
Being able to anticipate force will reduce injury | e.g. learn how to impact safely by spreading the energy (roll on falling)
29
Which biomechanical factors protect us from injury
Skin is very elastic and resists stretching
30
Which biomechanical factors make us vulnerable to injury
Blood vessels vulnerable to stretch - burst easily Semi-fluid brain is vulnerable to shearing/rotation - delicate nerves get damaged Bone is vulnerable to torsion (twisting) Hollow organs vulnerable to compression
31
What are the 3 main types of blunt force injury
Bruises Abrasions Lacerations
32
In which layer of the skin are blood vessels found
Subcutaneous fat | Branches come up to the surface
33
When does a bruise occur
When an object strikes the skin and the blood vessels below are torn and stretched beneath it Skin in not broken
34
What is a laceration
A more severe, full thickness injury
35
What is a stab
Short and deep wound | Weapon is plunged into the tissue - deeper in body than width/length on surface
36
What is an incision
Wide lesion on skin surface but not very deep Weapon dragged across Causes a full thickness injury
37
What is a cerebral contusion
A bruise to the brain
38
Do bruises occur in death
Not usually | The heart isn't pumping so there isn't enough pressure for the blood to leak out and spread
39
What is a vital phenomenon
Something that only occurs within life | Such as a bruise
40
Where do bruises most commonly occur
Within the subcutaneous fat | Some may leak into the dermis
41
Describe how bruises 'track'
Bruising can track/move with gravity and muscle movement as the blood moves e.g. impact to the forehead or a skull fracture can lead to a black eye This can take time so bruises may appear over a few days and then become bigger and darker (develop)
42
Do bruises usually match the shape of impact/weapon
This is rare The blood that leaks out will spread out in 3 dimensions Edges will be blurry so not a distinct shape
43
Describe how a tramline bruise forms
Usually due to the impact of a rod shaped object The vessels in the site of impact are compressed forming a central pale area Vessels either side rupture due to stretch and from the 2 parallel tramline bruises
44
What may an intradermal bruise show
As this is more superficial it may show the pattern of the object Example: stamp bruise However, seeing the exact tread is rare - requires very localised bleeding
45
What can seatbelt bruises tell you
Which side of the car the person was on - direction of bruise Useful if there is suspicion of swapping drivers
46
What causes a donut bruise
Caused by impact of a circular object such as a ball | Central pale area where vessels are compressed and circular bruise around
47
What does a curved bruise suggest
Weapon that has mobility such as a hose | Flexible weapons will also move around any convexities of the body
48
What should be included in the documentation of an injury
Site Precise location - usually in relation to an anatomical landmark Type of injury Shape - relation to common object (circle, pear, boat) Size - length, width, depth Associated features - injury to underlying/surrounding structure Clinical effects - haemorrhage, was it fatal, how did it affect patient
49
What is haemorrhage
The escape of blood from any part of the vascular system - veins, artery, heart Can be external - onto surface Internal - into a body cavity Or into tissues which is a bruise
50
What is the definition of a bruise
Leakage of blood from ruptured small vessels into the surrounding tissues - seen as discolouration through intact skin Due to blunt force trauma
51
What is a haematoma
A swollen bruise within a confined space
52
Which tissues can bruise
Any tissue can bruise
53
Are bruises tender
Yes typically | Tenderness can be elicited by pressing on the bruise
54
What is the difference between an internal and external bruise
External - visible on skin surface (may be masked on darker skin) Internal - not visible on skin surface too deep
55
List some of the difficulties with bruise interpretation
Site of bruise isn't always site of impact - tracking Appearance may be delayed Shape rarely reflects causal object Size rarely reflects severity of impact - e.g. minor impact can cause large bruise, especially in the elderly or alcoholics Accurate ageing is hard
56
Where do bruises track
Along the planes of least resistance | This can be natural or traumatic planes
57
What is the severity of a bruise dependent on
Degree of force Site of impact - loose fatty tissue bruise easily as vessels are poorly supported Age of victim - very young and very old Sex of victim - females bruise more easily as greater subcutaneous fat Obesity Natural disease - blood disorders Alcohol intake - alcoholics bruise easily and often, fall risk and clotting issues due to liver damage
58
Why do the elderly bruise easily
Connective tissues degenerate with age so blood vessels are less supported They tear very easily so everyday impacts can cause bruising Skin is thinner so bruises are more obvious - clear edges Called senile purpura
59
List the colour changes seen as a bruise ages
dark red - immediate - due to oxyHaemoglobin Dusky purple - after minutes - due to deoxyhaemoglobin Brown - after 1-3 days Green - after 4-5 days - due to biliverdin (Hb breakdown product) Yellow - after 7-10 days - due to bilirubin Disappears after 7-14 days Lots of variation between individuals
60
What is senile purpura
Distinct, well defined bruising in the elderly | Dark purple
61
Are bruises easy to age
No | Lots of individual variation so not an accurate process
62
Bruises on the face and ears are suggestive of what
Punching and kicking assaults | May also see bruising on the inside of the lips
63
Bruises on the upper neck are suggestive of what
Strangulation | May see fingertip marks
64
Bruises on the limbs are suggestive of what
Forceful restraint
65
Bruises on the back are suggestive of what
Counter pressure - being pressed against a hard flat surface such as wall/the floor etc Most common in spine or shoulder blades Or if patient has been lying down for a long period - tracking
66
Bruises of various ages are suggestive of what
Repeated assaults or abuse | Useful in child abuse cases
67
Resuscitation may cause bruising - where
Face, neck and chest
68
Are bruises on the shins normal or abnormal in children
Normal | Often occur through normal play, activity and falls
69
Describe the appearance of fingertip bruises
Similar size and age | Spacing between matches finger spread
70
Fingertip bruises on the thighs may be suggestive of what
Sexual assault | Even with absence of genital injury
71
What is lividity
Post-mortem phenomenon where blood pools in the vessels due to gravity and causes skin discoloration Can be confused with bruising but is not the same
72
What is the definition of an abrasion
A portion of the body surface from which the skin or mucous membrane has been removed by rubbing/friction Superficial or partial thickness injury - only involves epidermis and/or dermis Includes imprints and scraping/grazes
73
What causes an abrasion
Crushing or scraping of the epidermis/dermis Crushing is a vertical force - imprints into the skin Scraping is a tangiential force across the skin surface
74
What is the difference between a graze and a scratch
Graze is a scraping abrasion over a large area - such as road rash A scratch is a scraping abrasion over a fine point - e.g. from a fingernail
75
Do abrasions bleed a lot
No - bleeding is usually slight as the vessels are lower down in the skin They will heal quickly and won't leave a scar
76
Are abrasions clinically significant
Not really | Often overlooked by doctors as not usually severe
77
Describe an imprint abrasion
Underlying skin is crushed from the outside | Often leaves an imprint of the causal object or overlying clothing
78
What happens to an abrasion after death
It dries out Leaves an orange/brown, leathery appearance May look like parchment
79
What can cause an imprint abrasion
``` Footwear Tyre impressions Clothing weave Ligature weaves Seatbelts Vehicle parts in a RTA Weapon itself Hilt of knife ```
80
Describe a scrape abrasion
Object dragged across skin causes the epidermis to be scraped off and pushed to the 'finishing edge' - leaves skin tags Can show direction of scrape May bleed slightly is some dermal papillae are disrupted
81
What type of abrasion is road rash
Scrape abrasion
82
What is the forensic importance of abrasions
Most useful injury type Always occur at site of impact Often reflect the pattern of the causal object/surface Often indicate the direction of impact Possible transfer of trace evidence - grit or dirt
83
Can abrasions be aged
Not really Can tell if its healing but not really age it Will dry out and pucker
84
Bite marks are suggestive of what
May be seen in sexual assault and child abuse Can be a result of young siblings, pets, sporting collisions as well as assault or self-inflicted injury
85
What type of injury is a mouth mark
May be a combination of bruising, abrasion and laceration Teeth cause abrasions and bruising Laceration if sharp like an animal bite Suction leaves a central bruise - hickey
86
Why is mouth mark a better description than bite mark
Not just the teeth involved Also tongue, lips and suction force - tissue is drawn into the mouth Suction leaves a bruise - hickey
87
Describe the appearance of an animal bite
Will be deeply arched | Sharper teeth cause lacerations
88
Describe the appearance of a human bite
Circular or oval in shape | Shallow
89
What is the definition of laceration
Full thickness tearing of the skin due to stretching, pinning and crushing by blunt force trauma Irregular edges Can occur in any tissue
90
What are the 2 mechanisms of laceration
Crushing or splitting | Stretching or tearing
91
Where do crushing/splitting lacerations typically occur
Areas where skin overlies bone such as the scalp, eyebrow, cheek, knees, elbows and knuckles Blunt force in these areas - blows to head or falls Punches in the case of the knuckles
92
When do stretching/tearing laceration occur
When skin is stretched past its elastic limit
93
What are the physical features of a laceration
Ragged edges Tissue bridges in base - skin splits unevenly Associated bruises and abrasions - often on margins Minor bleeding despite size - associated with spasm/retraction of vessels Don't usually indicate shape of causal object - skin stretched or tears irregularly May hold trace evidence - splinters, paint chip from care
94
How might a laceration from a hammer strike appear
Circular laceration with abrasions Stellate splitting of laceration Glancing blows may have more of a moon shape
95
What is flaying
A type of stretching laceration | Seen in RTA - tires split skin then tear it off as they spin
96
What causes post-mortem lacerations
Oedematous or elderly skin can split when handled | Fingers can tear it when lifting the body
97
What is the clinical significance of lacerations
``` Haemorrhage is usually slight Often require suturing Foreign bodies and infection are common Heals by scarring May be confused with incision ```
98
What are the main differences between lacerations and incisions
Lacerations are blunt force - have tissue bridges, bruising in base and marginal abrasion Incisions are sharp force and so have no tissue bridges, bruises or abrasions Bleeding is slight in lacerations but profuse in incisions Trace evidence is often found in lacerations but is rare with incisions
99
In which layer of the skin are hair follicles and sweat glands found
Dermis
100
How can you differentiate between a bruise and lividity if unsure
Make an incision If there is blood in the tissue itself it is a bruise If not it is lividity

Forensic Medicine (13 decks)

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