1. No category

11/30/2013
Head and spine injuries
December 2013
Associate Professor Karin Brolin
Chalmers University of Technology
Acknowledgement:
Associate Professor Johan Davidsson and Professor Mats Svensson
have contributed to the presentation material.
What is essential to protect?
• Life supporting functions
– Brain
– Cervical spine (above C3)
• Quadriplegia above T1
• Paraplegia below T1
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Principal parts of the nervous system
•
Central nervous system (CNS):
•
Peripheral nervous system (PNS):
– brain
– spinal cord
– numerous, paired nerves joining CNS with
different parts of the body
– ganglia - clusters of nerve cells
system
Fig.Nervous
45.03(TE
Art)
Central
nervous
system
Brain
Peripheral
nervous
system
Spinal
cord
Sensory
pathways
Somatic
(voluntary)
nervous system
Sensory pathways
Motor pathways
Sympathetic
division
Motor
pathways
Autonomic
(involuntary)
nervous system
Parasympathetic
division
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
system
Fig.Nervous
45.03(TE
Art)
Central
nervous
system
Brain
Peripheral
nervous
system
Spinal
cord
Sensory
pathways
Somatic
(voluntary)
nervous system
Sympathetic
division
Motor
pathways
Autonomic
(involuntary)
nervous system
Parasympathetic
division
AIS examples by body region
AIS
Head
Thorax
Abdomen and
pelvic
contents
Spine
Extremities
and bony
pelvis
1
Headache or
dizziness
Single rib
fracture
Unconscious
< 1 hr.; linear
fracture
2-3 rib
fracture;
sternum
fracture
Acute strain
(no fracture or
disl.)
Minor fracture
without any
cord
involvement
Toe fracture
2
Abdominal
wall:
superficial
Spleen kidney
or liver:
laceration or
contusion
3
Unconscious
1-6 hrs.;
depressed
fracture
≥ 4 rib
fracture; 2-3
rib fracture
with hemoth.
or pneumoth.
Spleen or
kidney: major
laceration
Ruptured disc
with nerve
root damage
Knee
dislocation;
femur fracture
Tibia, pelvis or
patella: simple
fracture
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AIS examples by body region
AIS
Head
4
Unconscious
6-24 hrs.;
open fracture
5
Thorax
≥4 rib fracture
with hemoth.
Or pneumoth.;
flail chest
Unconscious> Aorta
24 hrs.; large laceration
hematoma
(partial
transection)
Abdomen and
pelvic
contents
Spine
Extremities
and bony
pelvis
Liver major
laceration
Incomplete
cord
syndrome
Kidney, liver
or colon
rupture
quadriplegia
Amputation or
crush obove
knee pelvis
crush (closed)
Pelvis crush
(open)
HEAD INJURIES
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Head anatomy
•
•
•
Scalp
Skull and facial bones
Brain and the nervous system
•
•
Complete head mass 4.5 kg
Brain mass around 1.65 kg
Skull and Facial bones
• Several fused bones
• Suture lines
• Mandible
• Large individual variations
Lateral view
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Skull base is irregular
• Irregular surface
– Ridges
• Small holes
– Arteries and veins
– Cranial nerves
• Foramen magnum
– Brain stem
Compact bone
Transversely isotropic:
C11
C
 12
C13
C
 0
 0

 0
C12
C13
0
0
C11
C13
0
0
C13
0
C33
0
0
C44
0
0
0
0
0
C44
0
0
0
0
0
0

0
0 
0

C0 
C0 = (C11C12)/2
5 coefficients
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Strength of trabecular bone
(a)
(b)
Compressive
Tensile
Corpus callosum
Thalamus
Lateral ventricle
Sensory processing
Movement
Hippocampus
Memory
Learning
Pons
Optic recess
Hypothalamus
Temperature, Emotions, Hunger, Thirst
Motor control
Sensory analysis
Sleep
Medulla oblongata
Breathing, Heart Rate,
Blood Pressure
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Head injuries
•
Skull Bone Fractures
•
•
Facial Bone Fractures
Soft tissue
•
Brain
– Linear
– Depressed
– Basilar
– Skin and scalp
– Blood vessels
– Sensory organs
– with skull injury
– with-out skull injury
What is so special about
Traumatic Brain Injury (TBI)?
Even a moderate bump can damage the brain.
The brain cannot be compressed without injury.
Damage to limbs may often be repaired while
brain damage many times causes permanent
harm.
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Frequency of
TBI in the US
10,000,000 per year world wide
India
Sweden
200,000 deaths
1 million injured
20,000
Langlois J, Rutland-Brown W, Wald M. The epidemiology and impact of traumatic
brain injury: a brief overview. J Head Trauma Rehabil. 21(5), pp 375-378, 2006
Traumatic Brain Injury
Other 5%
Suicide; 1%
Assault, 10%
Falls, 25%
Road traffic, 60%
Other; 1%
Center for Disease Control and Prevention, US
National Institute of Mental Health & Neuro Sciences, India
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Acute Symptoms following TBI
Mild Brain Injury
• Brief period of
unconsciousness
• Headache
• Confusion
• Dizziness
• Sensory problems
• Mood changes
• Concentration problems
Moderate to Severe
• Persistent headache
• Nausea
• Spasm
• Dilation of the eye
pupils
• Slurred speech
• Weakness or numbness
• Loss of coordination
• Increased confusion
Long term symptoms from TBI
• Trouble remembering, concentrating, making
decisions, and controlling impulses
• Suffer from serious motor, sensory, and
emotional impairments
• Not all TBI-related disabilities are readily
apparent to others. That's why TBI is the
"invisible epidemic"
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Type of injury
Traumatic Brain Injury
Diffuse Brain Injury
Focal Brain Injury
Laceration
Contusion
Hematoma
Concussion
Diffuse Axonal Injury
Injury mechanism from dynamic loading
•
Direct contact
– Linear acceleration
•
•
•
Deformation
Stress waves
Pressure gradients
•
•
Direct fracture
Indirect fracture (burst fracture)
•
•
Relative motion between skull
and brain
Shear in brain tissue
•
Non-contact
– Inertia properties
•
Relative motion between
skull and brain
– Negative pressure
– Cavitations
– Shear strains
– Rotational acceleration
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Radial vs. oblique impact
Radial impact
Oblique impact
Kleiven, Enhanced Safety of Vehicles 2007
Traumatic Brain Injury
Focal Brain Injury
Diffuse Brain Injury
Laceration
Contusion
Concussion
•
•
•
Coup
Contre-coup
Gliding
Hematoma
Diffuse Axonal Injury
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Contusions
•
Bruise of the brain common at inferior
surfaces of frontal and temporal lobes
•
Mechanism: Brain contact with rigid
intracranial structures.
Traumatic Brain Injury
Diffuse Brain Injury
Focal Brain Injury
Laceration
Concussion
Contusion
Diffuse Axonal Injury
Hematoma
•
•
•
•
Epidural
Subdural
Subarachnoidal
Intracerebal
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Hematoma
- Blood forms a hematoma that compresses the brain tissue
Bridging veins
Meningal artery
• Subdural
hematoma
• Epidural and
extradural
hematoma
• Rotation injury
• Fractures
Hematoma - Symptoms
•
Immediately to several weeks after a blow to the
head:
– Headache “The worst headache of their lives"
– Vomiting
– Slurred speech
– Pupils of unequal size
– Weakness in limbs on one side of your body
•
As more and more blood flows into the narrow space
between the brain and skull:
– Lethargy
– Unconsciousness
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Epidural and extradural hematoma
• Artery ruptures between dura and skull.
• The risk of dying is substantial.
• More common in children and teenagers.
• Mechanism: mostly temporal bone fracture
from falls and violence.
– Laceration from penetrating objects and
bone fragments
– Large contusions
– Tearing of bridging veins due to rotational
motions
– Age related due shrinkage of brain
Intracerebral hematoma
Subarachnoid hematoma
•
•
Artery ruptures.
Bleeding into the cerebrospinal fluid of the
sub-arachnoid space.
Permanent brain damage from ischemia or
from the presence of hematoma.
Mechanism: Rotational acceleration in
conjunction with aneurysm.
•
•
Subdural hematoma
• Veins rupture between dura and arachnoid.
• Acute, Sub-acute and Chronic
• Permanent brain damage may result.
• More common in very young and old.
• Mechanisms:
• Blood in the white matter of the brain.
• Combined with white matter shear injuries
• Blood irritates the brain tissues, causing
swelling or hematoma
• Mechanism: Laceration, sheer
deformation?
Traumatic Brain Injury
Focal Brain Injury
Diffuse Brain Injury
Laceration
Concussion
•
Mild – Classic
Diffuse Axonal Injury
Contusion
Hematoma
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Concussion
•
•
•
•
•
Anterograde and retrograde amnesia
Duration of amnesia correlates with the injury severity
Post concussion syndrome, which can include
memory problems, dizziness, and depression
Cerebral concussion is the most common head injury
seen in children
Mechanism: Rotational and linear acceleration of
head.
Traumatic Brain Injury
Focal Brain Injury
Diffuse Brain Injury
Laceration
Concussion
Contusion
Diffuse Axonal Injury
•
Hematoma
Mild – Moderate – Sever
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Diffuse Axonal Injury (DAI)
•
•
Lesions in white matter
– Corpus callosum, penduncles and
thalamus
Unconscious and vegetative state
– 90% with severe DAI never regain
consciousness
•
Car, sport and child abuse.
•
Mechanism: shearing forces due to rotational
acceleration. Stretching axons that traverse junctions
between areas of different density
DAI mechanism
•
•
•
Axon torn at the site of stretch.
Distal part degrades.
Secondary biochemical cascades largely responsible
for the damage to axons.
Corpus callosum
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What do we know?
•
Prevention is the best solution!
•
Medication, surgery etc second choice
– oxygen supply, maintaining adequate blood flow, and
controlling blood pressure
Injury risk measures
•
Linear acceleration
•
Rotational acceleration
•
Reality = combination of linear and rotational
•
Peak force for fracture
– Frontal impact: 4.0 – 6.2 kN
– Lateral impact: 2.0 – 5.2 kN
– Occipital impact: 12.5 kN
– Wayne State Tolerance Curve
– Injury threshold related to acceleration and brain mass
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Wayne State Tolerance Curve
• Fracture as function of
linear acceleration and
duration
• Forehead impacts only
• Based on cadaver and
animal experiments
• Assumption: Skull
fracture predicts brain
injury
Gurdjian E, Robert V, Thomas L. Tolerance curves of acceleration and intercranial
pressure and protective index in experimental head injury, J. Trauma 6(5), pp 600‐
604
Head Injury Criterion - HIC
• Linear acceleration (g)
• HIC36
• 36 ms interval
• threshold 1000 for 50th male
• Head Protection Criterion (HPC)
• HIC15
• 15 ms interval
• threshold 700 for 50th male
Kleinberger M et.al. Development of improved injury criteria for the assessment of advanced automotive restraint systems ‐ II, NHTSA report, Nov. 1999.
Widely used with Anthropometric Test Devices in consumer
testing and regulations
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Diffuse brain injury thresholds
0.05=reversible strain; concussion
0.20=irreversible strain; tissue disruption
Margulies S.S., Thibault L.E., A proposed tolerance criterion for diffuse axonal injury in
man, Journal of Biomechanics 2(8), 1992
Head injury criteria
• Linear acceleration (g)
Generalized Acceleration Model for Brain Injury Threshold
• Linear and rotational acceleration
• acr = 250 g, αcr = 10krad/s2
• Overall threshold = 1.0
• Rotational velocity & acceleration
• Updated 2013:
• Only rotational velocity
• Added directional dependency
• Rotational acceleration
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Head injury criteria
Gadd CW, National Research Council Publication No 977,
pp141‐144, 1961.
Versace J, A review of the severity index. 15th Stapp Car Crash Conference, SAE Technical Paper 710881, 1971.
Kleinberger M et.al. Development of improved injury criteria for the assessment of advanced automotive restraint systems , NHTSA report, Sept. 1998.
Newman J, A generalized acceleration model for brain injury
threshold (GAMBIT), IRCOBI Conference, 1986.
Takhounts E, Hasija V, Ridella S, et al, Kinematic rotational
brain injury criterion (BRIC), 22nd Enhanced Safety of
Vehicles Conference. Paper No. 11‐0263, 2011.
Takhounts E et.al. Development of Brain Injury Criteria (BrIC),
Stapp Car Crash Journal 57(Nov ), pp 243‐266, 2013
Kimpara H, and Iwamoto M, Mild Brain Injury Predictors Derived From Dummy 6DOF Motions, 40th International Workshop on Human Subjects for Biomechanical Research, Savannah‐GA (USA), 2012.
SPINE INJURY
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Spinal anatomy
•
Cervical spine (neck)
•
Thoracic spine
•
Lumbar spine
•
•
Sacrum
Coccyx
– Ribs
Anatomy
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The intervertebral disc
•
Purposes:
•
Hydrofilic gel
•
Collagen fibers in ground substance
– Damping
– Restrict relative translations between the vertebrae
– Allow for some rotation
– 90% to 70% water
– Fiber direction  60º
The intervertebral disc
•
10 times stiffer in compression than torsion,
shear or flexion.
•
The almost incompressible properties of the
nucleus pulposus result in tensile loading of the
collagen fibers when the disc is compressed.
•
•
Rate dependent properties
Viscoelasticity (fluid flow)
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Youngs
Modulus
(MPa)
500 - 1000
Poissons
Ratio
0.5 - 3
0.3
Ground
substance
1-3
0.45
Rubber
1.4
0.499
Oak
10,000
0.2
100
5
Steel
200,000
0.3
500
1
Yield
strain
(%)
Strain at
failure
(%)
Collagen
Elastin
Young’s
modulus
0.3
Tensile
strength
(MPa)
50 - 100
Strain at
failure
(%)
10 - 20
100 - 200
Stress at
failure
(MPa)
(MPa)
Collagen
500
10-20
Elastin
Ground
substance
3
130
Ligaments
20
Tendons
45-125
3
50-100
25
> 100
20
4
10
60
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Peripheral
nervous
system
Spinal injuries
•
AIS 3+ spine injuries are quite rare in motor vehicle
crashes.
•
AIS 1 neck injuries (whiplash) account for a
substantial portion of long term disabling injuries
– Sweden 55%
– India ?
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Epidemiology
Sever spinal cord injury
• 10.000 cases/year
in the US
– Motor vehicle
– Fall
– Diving
54%
16%
12%
• 20.000 cases/year
in India
– Traffic
– Fall
45%
35%
• male:female 3:1
• 20-40 years of age
Epidemiology
Sever spinal cord injury
•
In modern cars
•
Motorcyclist, mopeds and bikes
– Roll-over
– Unbelted all directions
– Forward facing children age <2 years
– All accident types
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Anthropometry explains children's
increased risk for neck injury
Head center of gravity
more superior in young
children.
Facet joints are more
horizontal.
Burdi, A. R., Huelke, D. F., Snyder, R. G., Lowrey, G. H. (1969/07)."Infants and children in
the adult world of automobile safety design: Pediatric and anatomical considerations for
design of child restraints." Journal of Biomechanics 2(3): 267-280
In automotive crashes…
•
If unbelted head contact the windscreen in frontal
crashes
– Axial compression
– Shear loading
– Bending
•
Minor soft tissue neck injuries due to inertia
– Axial tension
– Shear loading
– Bending
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Sever neck load - examples
Pedestrian accident
Bad design
Out of position airbag injuries
Sever neck loading
•
Pure compressive loading
– Jefferson fracture of the atlas (C1) is unstable.
– Burst fracture of vertebral bodies (C2-C7)
– Increasing load can give facet dislocation
•
Flexion-compression loading
– Dislocations (often at Occiput-C1)
•
Tension-extension loading
– Hangman’s fracture of C2
•
Lateral bending and compression loading
– Fractures on the compressed side
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Whiplash Associated Disorders (WAD)
- soft tissue injury
Injury mechanism ?
Prevention
Treatment
Diagnosis
Tension-extension loading, caused by inertia loading of the head.
http://www.mvd.chalmers.se/~mys
Injury mechanisms
•
•
•
•
•
Still not know – research ongoing
Facet joints ?
– Pain (>40%)
Pain sensitization.
Muscle ?
– Good prognosis
CNS ?
– Dorsal nerve root ganglion injury due to pressure
wave
Ligament ?
Disc ?
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Experimental studies
• Human subjects
• Animal models
Pullforce
x-acc.
Head-
Pull-rod
Backrest
z-acc.
Operatingtable
Rod
Straps
Angular
displacement
transducers
X
Coordinatesystem
Z
Linear displacement transducer
Professor Mats Svensson at Chalmers.
http://www.mvd.chalmers.se/~mys
RID 3D
Crash Dummies
BioRID II
http://www.mvd.chalmers.se/~mys
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Female rear dummy
Neck injury criteria
•
•
AIS3+
– Nij
=Fz/Fint+My/Mint
AIS1
– NIC
– Nkm
=0.2 arel + vrel2
= Fx/Fint+My/Mint
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Nij dummy values
proposed by NHTSA
Kleinberger M et.al. Development of improved injury criteria for the assessment of advanced automotive restraint systems ‐ II, NHTSA report, Nov. 1999.
NIC = Neck Injury Criterion
NIC = 0.2 arel + vrel2
arel = aT1 - ahead
ahead, Vhead
vrel = vT1 - vhead
50% risk:
NIC=25 m2/s2
NIC=15 m2/s2
aT1, VT1
Hypothesis: Pressure aberrations inside the spinal canal.
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Nkm Neck protection criterion
load case
Intercept value
Extension moment
47.5 Nm
Flexion moment
88.1 Nm
Shear
845 N
Euro-NCAP uses different threshold values depending on the crash pulse, the
critical Nkm ranges from 0.12 - 0.69 (van Ratingen et al. 2009)
Hypothesis: Linear combination of shear and y-moment is
responsible for relevant neck loading
Neck injury criteria
•
•
AIS3+
– Nij
=Fz/Fint+My/Mint
AIS1
– NIC
=0.2 arel + vrel2
– Nkm
=
Fx/Fint+My/Mint
Kleinberger M et.al. Development of improved injury criteria for the assessment of advanced automotive restraint systems , NHTSA report, Sept. 1998. Boström O, Svensson M, Aldman B, Hansson H, Håland Y, Lövsund P, Seeman T, Suneson A, Säljö A, Örtengren T (1996): A new neck injury criterion candidate based on injury findings in the cervical spinal ganglia after experimental neck extension trauma, Proc. IRCOBI Conf., pp. 123‐136 Schmitt K‐U, Muser M, Niederer P (2001): A new neck injury criterion candidate for rear‐end collisions taking into account shear forces and bending moments, Proc. ESV Conf. Schmitt K‐U, Muser M, Walz F, Niederer P (2002): Nkm — a proposal for a neck protection criterion for low speed rear‐end impacts, Traffic Injury Prevention, Vol. 3 (2), pp. 117‐126 Kullgren A, Eriksson L, Krafft M, Boström O (2003): Validation of neck injury criteria using reconstructed real‐life rear‐end crashes with recorded crash pulses, Proc. 18th ESV Conf 33
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Protective strategies
WHIPS (Volvo) 1998.
Self-aligning head restraint (SAAB) 1998.
34