Head and spine injuries -...

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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):– brain

– spinal cord

• Peripheral nervous system (PNS):– numerous, paired nerves joining CNS with

different parts of the body

– ganglia - clusters of nerve cells

Fig. 45.03(TE Art)Nervous system

Centralnervoussystem

BrainSpinalcord

Peripheralnervoussystem

Somatic(voluntary)

nervous system

Motorpathways

Sensorypathways

Autonomic(involuntary)

nervous system

Sympatheticdivision

Parasympatheticdivision

Sensory pathways

Motor pathways

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Fig. 45.03(TE Art)Nervous system

Centralnervoussystem

BrainSpinalcord


Somatic(voluntary)

nervous system

Motorpathways

Sensorypathways

Autonomic(involuntary)

nervous system

Sympatheticdivision

Parasympatheticdivision

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

AIS examples by body region

AIS Head Thorax Abdomen and pelvic contents

Spine Extremities and bony pelvis

1 Headache or dizziness

Single rib fracture

Abdominal wall: superficial

Acute strain (no fracture or disl.)

Toe fracture

2 Unconscious < 1 hr.; linear fracture

2-3 rib fracture; sternum fracture

Spleen kidney or liver: laceration or contusion

Minor fracture without any cord involvement

Tibia, pelvis or patella: simple fracture

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

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AIS examples by body region

AIS Head Thorax Abdomen and pelvic contents

Spine Extremities and bony pelvis

4 Unconscious 6-24 hrs.; open fracture

≥4 rib fracture with hemoth. Or pneumoth.; flail chest

Liver major laceration

Incomplete cord syndrome

Amputation or crush obove knee pelvis crush (closed)

5 Unconscious> 24 hrs.; large hematoma

Aorta laceration (partial transection)

Kidney, liver or colon rupture

quadriplegia 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 boneTransversely isotropic:

5 coefficients

C

C C C

C C C

C C C

C

C

C

11 12 13

12 11 13

13 13 33

44

44

0

0 0 0

0 0 0

0 0 0

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

C0 = (C11C12)/2

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Strength of trabecular bone

(b)(a)

Compressive Tensile

Corpus callosum

Medulla oblongataBreathing, Heart Rate,Blood Pressure

PonsMotor control Sensory analysisSleep

HypothalamusTemperature, Emotions, Hunger, Thirst

ThalamusSensory processingMovementLateral ventricle

Optic recess

HippocampusMemory Learning

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Head injuries• Skull Bone Fractures

– Linear– Depressed– Basilar

• Facial Bone Fractures• Soft tissue

– Skin and scalp– Blood vessels – Sensory organs

• Brain – 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

India Sweden

200,000 deaths

1 million injured 20,000

10,000,000 per year world wide

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

Other 5%

Falls, 25%

Road traffic, 60%

Assault, 10%

Traumatic Brain Injury

Center for Disease Control and Prevention, US

National Institute of Mental Health & Neuro Sciences, India

Other; 1%

Suicide; 1%

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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


Diffuse Brain Injury

Concussion

Hematoma

Focal Brain Injury

Contusion

Diffuse Axonal Injury

Laceration

Injury mechanism from dynamic loading

• Direct contact– Linear acceleration

• Deformation• Stress waves• Pressure gradients

– Negative pressure– Cavitations– Shear strains

• Direct fracture• Indirect fracture (burst fracture)

– Rotational acceleration• Relative motion between skull

and brain• Shear in brain tissue

• Non-contact– Inertia properties

• Relative motion between skull and brain

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Radial impact Oblique impact

Radial vs. oblique impact

Kleiven, Enhanced Safety of Vehicles 2007



Concussion

Hematoma

Focal Brain Injury

Contusion


Laceration

• Coup

• Contre-coup

• Gliding

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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.



Concussion

Hematoma

Focal Brain Injury

Contusion


Laceration

• Epidural

• Subdural

• Subarachnoidal

• Intracerebal

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Hematoma - Blood forms a hematoma that compresses the brain tissue

Meningal artery

• Epidural and extradural hematoma

• Fractures

Bridging veins

• Subdural hematoma

• Rotation injury

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 Subdural hematoma

Subarachnoid hematoma Intracerebral 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.

• Veins rupture between dura and arachnoid.• Acute, Sub-acute and Chronic• Permanent brain damage may result.• More common in very young and old.• Mechanisms:

– Laceration from penetrating objects and bone fragments

– Large contusions– Tearing of bridging veins due to rotational

motions– Age related due shrinkage of brain

• 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.

• 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, sheerdeformation?



Concussion

Hematoma

Focal Brain Injury

Contusion


Laceration

• Mild – Classic

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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.



Concussion

Hematoma

Focal Brain Injury

Contusion


Laceration

• 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 – Wayne State Tolerance Curve

• Rotational acceleration – Injury threshold related to acceleration and brain mass

• 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

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Wayne State Tolerance Curve

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

• Fracture as function of linear acceleration and duration

• Forehead impacts only• Based on cadaver and

animal experiments

• Assumption: Skull fracture predicts brain injury

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; concussion0.20=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)

• 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

Generalized Acceleration Model for Brain Injury Threshold

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Head injury criteriaGadd 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– Ribs

• Lumbar spine

• Sacrum

• Coccyx

Anatomy

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The intervertebral disc

• Purposes:– Damping– Restrict relative translations between the vertebrae– Allow for some rotation

• Hydrofilic gel– 90% to 70% water

• Collagen fibers in ground substance– 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)

Poissons Ratio

Tensile strength (MPa)

Strain at failure

(%) Collagen 500 - 1000 0.3 50 - 100 10 - 20

Elastin 0.5 - 3 0.3 100 - 200

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

Young’s modulus

(MPa)

Yield strain (%)

Strain at failure

(%)

Stress at failure (MPa)

Collagen 500 10-20 45-125

Elastin 3 130

Ground substance

3

Ligaments 20 25 > 100 20

Tendons 50-100 4 10 60

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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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EpidemiologySever spinal cord injury

• 10.000 cases/year in the US–Motor vehicle 54%

–Fall 16%

–Diving 12%

• 20.000 cases/year in India–Traffic 45%

–Fall 35%

• male:female 3:1

• 20-40 years of age

EpidemiologySever spinal cord injury

• In modern cars– Roll-over

– Unbelted all directions

– Forward facing children age <2 years

• Motorcyclist, mopeds and bikes– All accident types

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Anthropometry explains children's increased risk for neck injury

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

Head center of gravity more superior in young children.

Facet joints are more horizontal.

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

Bad design

Out of position airbag injuries

Pedestrian accident

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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http://www.mvd.chalmers.se/~mys

Whiplash Associated Disorders (WAD)- soft tissue injury

Prevention

Diagnosis

Treatment

Tension-extension loading, caused by inertia loading of the head.

Injury mechanism ?

Injury mechanisms

• Facet joints ?

–Pain (>40%)

• Muscle ?

–Good prognosis

• CNS ?

–Dorsal nerve root ganglion injury due to pressure wave

• Ligament ?

• Disc ?

Still not know – research ongoing

Pain sensitization.

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Experimental studies

• Human subjects• Animal models

Operating-table

Head-

BackrestPull-rod

Straps

Rod

Linear displacement transducer

Angular displacement transducers

z-acc.

x-acc.

Pull-force

X

Z

Coordinate-system

Professor Mats Svensson at Chalmers.


Crash Dummies

BioRID II

RID 3D

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Female rear dummy

Neck injury criteria

• AIS3+

– Nij =Fz/Fint+My/Mint

• AIS1

– NIC =0.2 arel + vrel2

– Nkm = Fx/Fint+My/Mint

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Nij dummy valuesproposed 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 = 0.2 arel + vrel2

arel = aT1 - ahead

vrel = vT1 - vhead

NIC = Neck Injury Criterion

ahead, Vhead

aT1, VT1

50% risk: NIC=25 m2/s2

NIC=15 m2/s2

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

Hypothesis: Linear combination of shear and y-moment is responsible for relevant neck loading

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)

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

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Protective strategies

Self-aligning head restraint (SAAB) 1998.

WHIPS (Volvo) 1998.

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