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Forensic Medicine > Injury Patterns, RTA and Head Injury > Flashcards

Injury Patterns, RTA and Head Injury Flashcards

1
Q

Why might someone injure themselves for personal gain

A

Spite, compensation, wasting time, malingering

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2
Q

What is self mutilation a feature of

A

Psychiatric illness

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3
Q

What are the features of self inflicted injury for personal gain

A

Cheeks, forehead, arms and legs targeted - visible areas

Sparing of eyes, nose, lips, ears & genitals - sensitive areas avoided

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4
Q

What are the features of self inflicted injury for self-mutilation

A

Criss-crossing incisions or stabs

Face, eyes and genitals targeted - sensitive areas targeted

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5
Q

Is blunt or sharp force injury favoured for self inflicted injury

A

Sharp force

Blunt force requires too much force and pain

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6
Q

What are the major features of self-inflicted injury

A 
Usually sharp force or gunshot
Accessible target sites
Clothes drawn aside
Hesitation wounds
Only a few potentially fatal
Evidence of previous self-harm
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7
Q

What features suggest accidental injury

A

Can be any type of injury
Not aimed or grouped at a target site - usually scattered
Clothing usually involved
Defensive injuries are possible if they saw the object coming

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8
Q

What are stab wounds around the genitals suggestive of

A

A sexual component to the attack
The act of the weapon penetrating the flesh can represent sexual penetration

Sometimes the abdomen may also represent this

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9
Q

What injury patterns suggest an assault

A 
Can be any type of injury 
Aimed at target sites
Multiple injuries
Clothing involved
Several may be potentially fatal
Defensive injuries common
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10
Q

What injury pattern occurs with punches targeted to the face

A

Black eyes
Nasal fracture
Bruising & lacerations to lips
Bruises, abrasions & lacerations to cheeks, chin & ears - parts of face that ‘stick out’

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11
Q

What injury pattern occurs with a shod foot assault

A

Lacerations to eyebrows, cheeks & ears -parts of face that ‘stick out’
Fractures of maxilla, orbits, zygoma - bony ridges are vulnerable
Heel stamps give a D shaped outline bruise/abrasion

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12
Q

How can a shod foot assault cause death

A

Direct trauma
Airway obstruction
Internal bleeding
Duodenal perforation

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13
Q

How can a shod foot assault lead to airway obstruction

A

Blood - if inhaled it can block the airway
Tongue
Mobile facial fractures

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14
Q

How can a shod foot assault lead to internal bleeding

A

Can lacerate the organs

Spleen is vulnerable to rupture or being pierced by broken ribs

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15
Q

How can a shod foot assault lead to duodenal perforation

A

Force can pin duodenum against the vertebral column with blunt force and leads to perforation
Leaks slowly that leads to a peritonitis (death over hours or days)

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16
Q

What evidence can be gained in a shod foot assault beside the injury pattern

A

Trace evidence can be found in the shoe itself

Tread patterns can be seen in stamping injuries - must be accurately documented

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17
Q

How can fat form an embolism

A

In blunt force injuries the fat and vessels are disrupted and fat can enter the bloodstream
Fractures can also allow fat from the marrow to enter the circulation

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18
Q

What determines survival and capability after injury

A

Site of injury & structures damages
Degree of blood loss
Rate of blood loss

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19
Q

What are some of the early complications of injury

A

Haemorrhage
Loss of function
Fat embolism
Air embolism

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20
Q

What are some of the late complications of injury

A 
Infection
Pneumonia
ARDS (shock lung)
Deep vein thrombosis & pulmonary
embolism - worse when lying still for long periods 
Renal failure
Multi-organ failure (kidneys, liver, heart)
Disseminated Intravascular Coagulation
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21
Q

What is the equation for vehicle crash energy

A

E = mph2 x 0.034

/Stopping distance

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22
Q

What are the major contributory factors to RTAs

A

Human error is the major one (speed is biggest, fatigue, inattention)
Road conditions (bend, leaves, visual obstruction)
Environmental (weather - ice, rain, fog)
Mechanical failure - quite rare
Intoxication - tested for
Natural disease – collapse at wheel (relatively rare)

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23
Q

What are the primary pedestrian injuries in a RTA

A

Primary injury is first point of impact
Usually the bumper striking the legs (in adults)
Outcome depends on vehicle and pedestrian height

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24
Q

What are the secondary pedestrian injuries in a RTA

A

Injuries which occur after initial impact on legs , often strikes the thigh and then roll up onto car
Bonnet strikes thigh, pelvis and chest
Windscreen and pillars strikes chest and head

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25
Q

What are the tertiary pedestrian injuries in a RTA

A

Usually occur when pedestrian is thrown onto the ground, roadside objects or other vehicles
These can then cause tertiary injury
They can also then be run over

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26
Q

What injuries can occur when someone is ran over

A

Can be dragged and rolled under vehicle and hit by wheels or other parts of the chasse
Patterned imprint abrasions from tyres, underneath of vehicle
Flaying lacerations (with minor bruising)
Oil / dirt staining of skin

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27
Q

How can the height of the pedestrian affect the injury caused by RTA

A

Children will be struck lower in their center of gravity by a car - usually thrown forward and under

Adults being taller are struck on the legs and are thrown up
Will be struck lower in CoG if it is a van/lorry

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28
Q

What evidence can indicate speed of impact

A

Road markings - skid marks etc.

Throw distance - faster the car the further they are thrown

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29
Q

How does speed impact survival

A

Faster speed = lower survival
Impact at 30 mph – 80% survival rate
Impact at 40 mph – 80% fatality rate

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30
Q

Describe the wrap around pedestrian injury pattern

A

Most common pattern in RTA
Bumper strikes leg (below CoG) and pedestrian ‘wraps around’ the bonnet/bumper
Pedestrian is thrown onto the car and then off by the impact
Throw distance indicates speed

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31
Q

Describe the forward projection pedestrian injury pattern

A

Pedestrian is struck at or above C of G- less common
Then thrown forwards and down
At risk of getting run over
Occurs when an adult is struck by high fronted vehicle or a child struck by car

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32
Q

Describe the wing top pattern of pedestrian injury

A

Pedestrian struck by front wing

Carried over wing and falls off to side

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33
Q

Describe the roof top pattern of injury

A

Occurs at high speed
Pedestrian goes over the bonnet and onto the roof
There is secondary impact with roof of vehicle and then they are thrown off the back
Also called ‘running under’ as car goes under pedestrian

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34
Q

Describe the somersault pattern of injury

A

Occurs at high speed
Thrown high into air so there is no secondary impact with vehicle.
Tertiary impact with road

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35
Q

Describe the features if a bumper injury

A

Usual height of bumper is 40-50 cm - lower if breaking, higher if car is accelerating
Will strike strikes upper tibia of adult, femur of child
Resulting abrasion is measured as distance above heel to determine height
In adults it will cause a tibial fracture - wedge # at point of impact (due to angulation), spiral # at weakest point (due to rotational force)
Associated laceration and bruising may be complicated and harder to analyse

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36
Q

How can pedal marks help a crash investigation

A

Marks on pedal or sole can show which pedal was being pressed at the time of impact
Were they breaking or accelerating

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37
Q

What is the purpose of a car crumpling

A

It offers protection to those within the car - side impact bars also help
Absorbs the energy of the crash
Better at the front and rear of most cars as greater distance but poor on side impacts

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38
Q

Describe the mechanism of injury after a frontal impact

A

Occupants are thrown towards the point of impact
Knees strike parcel shelf or dashboard
May get bracing injuries to legs (+ driver’s arms) - forces travel up limbs and cause fractures
Shoe soles marked by pedals - pushed into sole by impact

Then the occupant will continue up and forwards
Head strikes windscreen, roof or “A” pillar
Chest strikes steering wheel or dashboard

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39
Q

Which parts of the car commonly injure the occupants during a RTA

A 
Dashboard and parcel shelf
Steering wheel and pedals 
Windscreen and pillars
Seat belt injuries
Airbag injury
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40
Q

How do seatbelts prevent injury in a RTA

A

Restrain body during deceleration - keep away from wheel
Spread area of deceleration force and duration of impact - stretch
Reduce impact with steering wheel and dash
Prevent ejection during rollover

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41
Q

How do airbags prevent injury in a RTA

A

Restrain upper torso during deceleration
Spread area of deceleration force and duration of impact - broad area of contact
Reduce impact with steering wheel, dash and car interior

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42
Q

What injuries can seatbelts cause

A

Can injure the neck, chest, abdomen
Bruise show it was being worn at the time of accident
Can cause friction tears/burns on clothing

43
Q

How can airbags cause injury

A

Injured by the module cover
Neck hyperextension - can be dangerous
Bag-slap

44
Q

List common head and neck injuries in car occupants in a RTA

A

Skull fracture
Brain injury and diffuse traumatic axonal injury
Cervical spine fracture

45
Q

List common chest injuries in car occupants in a RTA

A

Rib and sternal fractures - due to impact with wheel etc
Contusions and laceration to heart and lungs - can be fatal
Transection of aorta (classic deceleration injury) - not due to impact but heart continuing forward and shears off
Haemothorax may be rapidly fatal- seen after laceration and transections

46
Q

List common abdominal injuries in car occupants in a RTA

A

Lacerated liver, spleen, kidney, bowel, diaphragm
Pelvic #
Spinal fracture

47
Q

List common lower limb injuries in car occupants in a RTA

A

Pelvic or femoral fracture

Arms and leg fractures

48
Q

How can you identify the driver in a RTA

A

Injuries can be matched to vehicle interior - e.g. diagonal seat belt injuries or dicing injury from windows
Can get transference of trace materials such as blood, hair, tissue on the windscreen, dash etc
Clothing fibres
Footwear impressions from pedals

49
Q

Why might you need to use forensic evidence to identify the driver

A

If there is suspected denial by disqualified or intoxicated driver - particularly if there are fatalities
People may have changed positions post-crash to avoid blame

50
Q

What are the physical features of vehicular suicide

A

Usually a single vehicle impact - one car striking a stationary object
Stationary object
Seat belt not worn
No sign of avoidance - no skid marks or breaking evidence
Intoxication - dutch courage

51
Q

What are the psychological features of vehicular suicide

A

Depression - recent
Previous RTA
Substance abuse
Precipitating event - bereavement, divorce etc
Recent erratic driving - almost a practice

52
Q

Why are motorcyclists so vulnerable in RTAs

A

Travel at high speed
Unstable 2 wheel vehicle (tips easy)
Nothing around them to protect them

53
Q

List the common injuries affecting motorcyclists in a RTA

A

Primary leg injuries
Secondary injuries - Head & neck, chest (heart and lung lac, rib#, haemothorax), abdomen, limbs
Tertiary injuries from road, other vehicles, etc.
Vulnerable to all types

54
Q

Which direction of impact is most dangerous in an RTA

A

Side impact is more dangerous

Structural integrity of car is less here

55
Q

What are the 2 main types of head injury

A

Penetrating - e.g. gunshot
Non-penetrating - blunt force trauma
(more common)

56
Q

List the most frequent causes of head injury

A

RTA
Assault
Acciden

57
Q

Why is the head vulnerable to injury

A

It is heavy, freely mobile & unstable
Vulnerable to impact, rotation, acc/decel - all shake brain around within skull
This movement makes it prone to injury

Major cause of death and disability

58
Q

What determines the prognosis of head injury

A

Prognosis related to length and depth of unconsciousness
Longer and deeper = worse
Can be estimated by the glasgow coma scale

59
Q

What is the Glasgow Coma Scale

A

Scale out of 15 that indicates level of consciousness
Indicates prognosis
Motor response out of 6 (voluntary to no movement)
Verbal response out of 5 (orientated to no response)
Ocular response out of 4 (spontaneous to eyes closed)

60
Q

Describe the structure of the dura

A

Lining of the brain
Reflects to divide the brain
- into R and L hemisphere by falx
- into cerebrum and cerebellum by tentorium cerebelli

61
Q

List the ‘layers’ of the head

A

Scalp - thick layer of skin and subcutaneous tissue
Aponeurosis - connective tissue
Skull - 3 layers (outer table, spongy middle called diplo, inner table)
Dura - thick membrane lining interior skull
Arachnoid - thin membrane
Pia mater
Brain

62
Q

Why is the brain vulnerable to swelling

A

Due to the confines of the skull

Easily compressed

63
Q

List the most common primary head injury

A

Scalp - abrasion, bruising, laceration
Skull fracture
Intracranial haemorrhage
Brain Injury

64
Q

Can the brain be injured without external signs of injury

A

Yes

Vulnerable to damage by impact, falls or shaking even if outside is relatively unaffected

65
Q

List common scalp injury

A

Abrasion
Bruising
Haematoma (bruise + swelling) - scalp is vulnerabale to this
Laceration - will cause profuse bleeding as scalp is very vascular

66
Q

How much force is required to cause a skull fracture

A

Depends on:
Thickness of hair - provides a ‘cushion’
Thickness of scalp
Thickness of skull (anatomically variable)

Site of impact - vulnerable to side impact as skull is thin here
- thicker at front

Direction of impact

67
Q

How can hair protect the head from injury

A

It can act as cushion as hair rolls over each other to disseminate energy
depends on the thickness

68
Q

Which section of the skull is thickest

A

The front - most resistant to impact

Can also get internal thickening at the front too

69
Q

List the main types of skull fracture

A 
Linear - straight line
Comminuted (>2 fragments)
Radiating - central origin/impact point 
Spider’s web - concentrically linked radial fractures 
Depressed - fragments from comminuted are pushed down toward brain (dangerous to underlying brain)
Hinge - across base of skull 
Ring - encircling the foramen magnum 
Contre-coup - opposite point of impact
70
Q

When are hinge and ring skull fractures often seen

A

RTA - common in motorcyclists

Occurs with a strike to jaw (transmits to base of skull) or base of skull

71
Q

List common signs of skull fracture

A

Battles sign - bruise behind ear

72
Q

What is diastasis

A

When a fracture meets a point of fusion in the skull (suture)
Fracture will then follow the suture line
Usually very irregular line

73
Q

What is a haematoma

A

Haemorrhage forming a distinct mass

74
Q

List the types of intracranial haemorrhage

A

Extradural haematoma - outside dura
Subdural haemorrhage/haematoma - under dura
Subarachnoid haemorrhage - under arachnoid mater
Intracerebral haemorrhage - within brain itself

75
Q

What causes an extradural haematoma

A

Usually due to a blow to the temple - bone is thin
A fracture tears an artery within the inner table of the skull - usually the middle meningeal artery under temporal bone
Rarely may be caused by a venous sinus
Blood then accumulates over the dura surface and pushes/strips it off the skull
If untreated it can be fatal

76
Q

What are the features of a extradural haematoma

A

May lose consciousness at event but may recover and have a lucid interval
As haematoma progresses and accumulates the pressure effects will eventually lead to loss of consciousness
Untreated it can be fatal

77
Q

How does an extradural haemorrhage affect the surrounding structures

A

Arterial bleeding forcibly strips dura off skull as blood accumulates
Localised to enlarging haematoma by dura (keeps it in place)

78
Q

How do you manage a extradural haemorrhage

A

Surgical decompression can be lifesaving

Releases pressure on the brain

79
Q

What causes a subdural haemorrhage

A

Usually a fall or a blow to the head - can be minor
Not usually associated with skull fracture
Shearing of bridging veins spanning subdural space
Blood spreads widely and accumulates beneath the dura
Blood accumulates and can compress the underlying brain

80
Q

Which groups are vulnerable to subdural haemorrhage

A

Alcoholics
Elderly
Children

81
Q

How does a subdural haemorrhage present

A

Often asymptomatic (incidental finding)
Can be fatal immediately or later as it accumulates
Compression effect on the brain can be fatal

82
Q

What can cause a subarachnoid haemorrhage

A

Natural cause - rupture of a berry aneurysm in the CIrcle of Willis
Laceration or contusion to brain surface after trauma - e.g. vessels tear after blow to head
Blow to the chin or jaw can lead to a Traumatic Basal SAH

83
Q

Describe a Traumatic Basal SAH

A

Blow to the chin or jaw jerk causes a stretching or rupture of the vertebral or basal artery (vulnerable at point of entry to cranial cavity
Causes immediate collapse and death within minutes
Strong association with alcohol intoxication - more likely to get in fight and lack protective reflexes
Can be due to the ‘unlucky’ single punch - culpable homicide

84
Q

What can cause an intracerebral haemorrhage

A

Natural - rupture of a small artery which may occur due to hypertension (stress from within vessel)

Traumatic - contusion or laceration to brain surface, shearing and tearing of the deep blood vessels
Blood accumulates in the brain

85
Q

Describe coup and contra-coup contusions

A

Coup contusions occur at the point of impact and tend to be localised
Usually due to a direct blow

Contra-coup contusions occur diagonally opposite the point of impact and are often extensive
Occur due to the brain gliding over rough interior of skull - more common at the back of skull
Usually due to a fall (more common if falling backwards)

86
Q

What is cerebral contusion

A

Bruising to the brain surface

87
Q

Which is diffuse traumatic axonal injury

A

Disruption of the nerve fibres across the brain following traumatic injury - shearing and tearing of nerves
Typically occurs in the white matter
Due to rotation and accel/decel forces

88
Q

List the major types of brain injury that can occur after trauma

A

Cerebral contusion
Cerebral laceration - impact or fracture
Diffuse Traumatic Axonal Injury -fatal nerve fibre disruption
Cerebral swelling and hypoxia

89
Q

Why does cerebral swelling lead to hypoxia

A

The swelling presses on the vessels and reduces blood flow

90
Q

What can cause diffuse axonal injury

A

RTA
Blows or kicks to a mobile head

Brain is shaken and there is tearing of the nerve fibres at a microscopic level
Typically occurs in the white matter
Effect is usually immediate

91
Q

How can you diagnose diffuse traumatic axonal injury

A

Difficult to detect
Typically occurs in the white matter
May see small haemorrhage (naked eye)
Usually based on microscopy - changes occur over several hours/days
Beta Amyloid Precursor Protein in immunostains (2-4 h)
Thickened axons seen with Silver stains (12-24 h)
Axonal retraction bulbs in white matter (1 d+)

92
Q

How does concussion present

A

Transient loss of consciousness
Retrograde amnesia - forget before the impact
Damage will spontaneously reverse

93
Q

What causes concussion

A

Temporary nerve cell dysfunction due to impact

No residual structural damage to the nerves so it is reversible

94
Q

List some of the secondary effects of head injury

A 
Death - sudden or delayed 
Raised Intracranial pressure
Brain swelling – common 
Cerebral hypoxia
Late complications include meningitis, abscess or post-traumatic epilepsy
95
Q

What are the risks of BFT when very intoxicated

A

Blunt force trauma to a highly intoxicated individual is very dangerous
Even minor blows can have a big effect
Sudden death is very common

96
Q

Describe the mechanism of death due to a head injury in a drunk person

A

Brain and neurones may be sensitised by alcohol
Blows cause jerking movements to neck
This jerking movement can cause brainstem concussion
Leads to acute brainstem dysfunction which affects the cardiac and respiratory symptoms
Can cause fatal respiratory arrest or cardiac arrhythmia

97
Q

List the common locations for brain herniation

A

Subfalcine herniation of cingulate gyrus - under the falx cerebra
Subtentorial herniation of cerebrum under tentorial edge
Tonsillar coning of cerebellum into foramen magnum

98
Q

What are the secondary effects of herniation

A

Can get infarction and necrosis at the herniation sites

99
Q

Why are pedestrians so vulnerable on RTA

A

Don’t have anything surrounding them for protection

100
Q

What can primary bumper injuries tell you about an accident

A

Height of injury on the legs is measured as distance from ankle
Can be matched to height of vehicle
If car was speeding up on approach the bumper tends to hit higher (rise)
If breaking it may hit lower

101
Q

What are the patterns of car impact

A 
Head on with another car 
Head on with stationary object 
Rear impact 
Side impact - passengers vulnerable as less crumple zone 
Side swipe 
Roll over

May be post-crash fires but rare these days

102
Q

What is the most common type of RTA

A

Car impacts

103
Q

Car occupants are vulnerable to injury from what features

A

Deceleration
Whiplash
Parts of the car interior - dashboard, steering wheel, pedals, windscreen and pillars
Seat belt injuries
Intrusion - from side impact, causes unilateral injury to chest and legs in particular
Greater the intrusion the more dangerous to occupants
Ejection - very dangerous, usually if seatbelt isn’t worn or fails

Forensic Medicine (13 decks)

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