Injury Patterns, RTA and Head Injury Flashcards
Why might someone injure themselves for personal gain
Spite, compensation, wasting time, malingering
What is self mutilation a feature of
Psychiatric illness
What are the features of self inflicted injury for personal gain
Cheeks, forehead, arms and legs targeted - visible areas
Sparing of eyes, nose, lips, ears & genitals - sensitive areas avoided
What are the features of self inflicted injury for self-mutilation
Criss-crossing incisions or stabs
Face, eyes and genitals targeted - sensitive areas targeted
Is blunt or sharp force injury favoured for self inflicted injury
Sharp force
Blunt force requires too much force and pain
What are the major features of self-inflicted injury
Usually sharp force or gunshot Accessible target sites Clothes drawn aside Hesitation wounds Only a few potentially fatal Evidence of previous self-harm
What features suggest accidental injury
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
What are stab wounds around the genitals suggestive of
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
What injury patterns suggest an assault
Can be any type of injury Aimed at target sites Multiple injuries Clothing involved Several may be potentially fatal Defensive injuries common
What injury pattern occurs with punches targeted to the face
Black eyes
Nasal fracture
Bruising & lacerations to lips
Bruises, abrasions & lacerations to cheeks, chin & ears - parts of face that ‘stick out’
What injury pattern occurs with a shod foot assault
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
How can a shod foot assault cause death
Direct trauma
Airway obstruction
Internal bleeding
Duodenal perforation
How can a shod foot assault lead to airway obstruction
Blood - if inhaled it can block the airway
Tongue
Mobile facial fractures
How can a shod foot assault lead to internal bleeding
Can lacerate the organs
Spleen is vulnerable to rupture or being pierced by broken ribs
How can a shod foot assault lead to duodenal perforation
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)
What evidence can be gained in a shod foot assault beside the injury pattern
Trace evidence can be found in the shoe itself
Tread patterns can be seen in stamping injuries - must be accurately documented
How can fat form an embolism
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
What determines survival and capability after injury
Site of injury & structures damages
Degree of blood loss
Rate of blood loss
What are some of the early complications of injury
Haemorrhage
Loss of function
Fat embolism
Air embolism
What are some of the late complications of injury
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
What is the equation for vehicle crash energy
E = mph2 x 0.034
/Stopping distance
What are the major contributory factors to RTAs
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)
What are the primary pedestrian injuries in a RTA
Primary injury is first point of impact
Usually the bumper striking the legs (in adults)
Outcome depends on vehicle and pedestrian height
What are the secondary pedestrian injuries in a RTA
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
What are the tertiary pedestrian injuries in a RTA
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
What injuries can occur when someone is ran over
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
How can the height of the pedestrian affect the injury caused by RTA
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
What evidence can indicate speed of impact
Road markings - skid marks etc.
Throw distance - faster the car the further they are thrown
How does speed impact survival
Faster speed = lower survival
Impact at 30 mph – 80% survival rate
Impact at 40 mph – 80% fatality rate
Describe the wrap around pedestrian injury pattern
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
Describe the forward projection pedestrian injury pattern
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
Describe the wing top pattern of pedestrian injury
Pedestrian struck by front wing
Carried over wing and falls off to side
Describe the roof top pattern of injury
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
Describe the somersault pattern of injury
Occurs at high speed
Thrown high into air so there is no secondary impact with vehicle.
Tertiary impact with road
Describe the features if a bumper injury
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
How can pedal marks help a crash investigation
Marks on pedal or sole can show which pedal was being pressed at the time of impact
Were they breaking or accelerating
What is the purpose of a car crumpling
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
Describe the mechanism of injury after a frontal impact
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
Which parts of the car commonly injure the occupants during a RTA
Dashboard and parcel shelf Steering wheel and pedals Windscreen and pillars Seat belt injuries Airbag injury
How do seatbelts prevent injury in a RTA
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
How do airbags prevent injury in a RTA
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
What injuries can seatbelts cause
Can injure the neck, chest, abdomen
Bruise show it was being worn at the time of accident
Can cause friction tears/burns on clothing
How can airbags cause injury
Injured by the module cover
Neck hyperextension - can be dangerous
Bag-slap
List common head and neck injuries in car occupants in a RTA
Skull fracture
Brain injury and diffuse traumatic axonal injury
Cervical spine fracture
List common chest injuries in car occupants in a RTA
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
List common abdominal injuries in car occupants in a RTA
Lacerated liver, spleen, kidney, bowel, diaphragm
Pelvic #
Spinal fracture
List common lower limb injuries in car occupants in a RTA
Pelvic or femoral fracture
Arms and leg fractures
How can you identify the driver in a RTA
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
Why might you need to use forensic evidence to identify the driver
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
What are the physical features of vehicular suicide
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
What are the psychological features of vehicular suicide
Depression - recent
Previous RTA
Substance abuse
Precipitating event - bereavement, divorce etc
Recent erratic driving - almost a practice
Why are motorcyclists so vulnerable in RTAs
Travel at high speed
Unstable 2 wheel vehicle (tips easy)
Nothing around them to protect them
List the common injuries affecting motorcyclists in a RTA
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
Which direction of impact is most dangerous in an RTA
Side impact is more dangerous
Structural integrity of car is less here
What are the 2 main types of head injury
Penetrating - e.g. gunshot
Non-penetrating - blunt force trauma
(more common)
List the most frequent causes of head injury
RTA
Assault
Acciden
Why is the head vulnerable to injury
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
What determines the prognosis of head injury
Prognosis related to length and depth of unconsciousness
Longer and deeper = worse
Can be estimated by the glasgow coma scale
What is the Glasgow Coma Scale
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)
Describe the structure of the dura
Lining of the brain
Reflects to divide the brain
- into R and L hemisphere by falx
- into cerebrum and cerebellum by tentorium cerebelli
List the ‘layers’ of the head
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
Why is the brain vulnerable to swelling
Due to the confines of the skull
Easily compressed
List the most common primary head injury
Scalp - abrasion, bruising, laceration
Skull fracture
Intracranial haemorrhage
Brain Injury
Can the brain be injured without external signs of injury
Yes
Vulnerable to damage by impact, falls or shaking even if outside is relatively unaffected
List common scalp injury
Abrasion
Bruising
Haematoma (bruise + swelling) - scalp is vulnerabale to this
Laceration - will cause profuse bleeding as scalp is very vascular
How much force is required to cause a skull fracture
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
How can hair protect the head from injury
It can act as cushion as hair rolls over each other to disseminate energy
depends on the thickness
Which section of the skull is thickest
The front - most resistant to impact
Can also get internal thickening at the front too
List the main types of skull fracture
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
When are hinge and ring skull fractures often seen
RTA - common in motorcyclists
Occurs with a strike to jaw (transmits to base of skull) or base of skull
List common signs of skull fracture
Battles sign - bruise behind ear
What is diastasis
When a fracture meets a point of fusion in the skull (suture)
Fracture will then follow the suture line
Usually very irregular line
What is a haematoma
Haemorrhage forming a distinct mass
List the types of intracranial haemorrhage
Extradural haematoma - outside dura
Subdural haemorrhage/haematoma - under dura
Subarachnoid haemorrhage - under arachnoid mater
Intracerebral haemorrhage - within brain itself
What causes an extradural haematoma
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
What are the features of a extradural haematoma
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
How does an extradural haemorrhage affect the surrounding structures
Arterial bleeding forcibly strips dura off skull as blood accumulates
Localised to enlarging haematoma by dura (keeps it in place)
How do you manage a extradural haemorrhage
Surgical decompression can be lifesaving
Releases pressure on the brain
What causes a subdural haemorrhage
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
Which groups are vulnerable to subdural haemorrhage
Alcoholics
Elderly
Children
How does a subdural haemorrhage present
Often asymptomatic (incidental finding)
Can be fatal immediately or later as it accumulates
Compression effect on the brain can be fatal
What can cause a subarachnoid haemorrhage
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
Describe a Traumatic Basal SAH
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
What can cause an intracerebral haemorrhage
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
Describe coup and contra-coup contusions
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)
What is cerebral contusion
Bruising to the brain surface
Which is diffuse traumatic axonal injury
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
List the major types of brain injury that can occur after trauma
Cerebral contusion
Cerebral laceration - impact or fracture
Diffuse Traumatic Axonal Injury -fatal nerve fibre disruption
Cerebral swelling and hypoxia
Why does cerebral swelling lead to hypoxia
The swelling presses on the vessels and reduces blood flow
What can cause diffuse axonal injury
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
How can you diagnose diffuse traumatic axonal injury
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+)
How does concussion present
Transient loss of consciousness
Retrograde amnesia - forget before the impact
Damage will spontaneously reverse
What causes concussion
Temporary nerve cell dysfunction due to impact
No residual structural damage to the nerves so it is reversible
List some of the secondary effects of head injury
Death - sudden or delayed Raised Intracranial pressure Brain swelling – common Cerebral hypoxia Late complications include meningitis, abscess or post-traumatic epilepsy
What are the risks of BFT when very intoxicated
Blunt force trauma to a highly intoxicated individual is very dangerous
Even minor blows can have a big effect
Sudden death is very common
Describe the mechanism of death due to a head injury in a drunk person
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
List the common locations for brain herniation
Subfalcine herniation of cingulate gyrus - under the falx cerebra
Subtentorial herniation of cerebrum under tentorial edge
Tonsillar coning of cerebellum into foramen magnum
What are the secondary effects of herniation
Can get infarction and necrosis at the herniation sites
Why are pedestrians so vulnerable on RTA
Don’t have anything surrounding them for protection
What can primary bumper injuries tell you about an accident
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
What are the patterns of car impact
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
What is the most common type of RTA
Car impacts
Car occupants are vulnerable to injury from what features
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
