Head and spine injuries
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 1 11/30/2013 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 2 11/30/2013 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 3 11/30/2013 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 4 11/30/2013 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 5 11/30/2013 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 = (C11C12)/2 5 coefficients 6 11/30/2013 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 7 11/30/2013 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. 8 11/30/2013 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 9 11/30/2013 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" 10 11/30/2013 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 11 11/30/2013 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 12 11/30/2013 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 13 11/30/2013 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 14 11/30/2013 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 15 11/30/2013 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 16 11/30/2013 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 17 11/30/2013 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 18 11/30/2013 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 19 11/30/2013 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 20 11/30/2013 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 21 11/30/2013 Spinal anatomy • Cervical spine (neck) • Thoracic spine • Lumbar spine • • Sacrum Coccyx – Ribs Anatomy 22 11/30/2013 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) 23 11/30/2013 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 24 11/30/2013 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 ? 25 11/30/2013 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 26 11/30/2013 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 27 11/30/2013 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 28 11/30/2013 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 ? 29 11/30/2013 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 30 11/30/2013 Female rear dummy Neck injury criteria • • AIS3+ – Nij =Fz/Fint+My/Mint AIS1 – NIC – Nkm =0.2 arel + vrel2 = Fx/Fint+My/Mint 31 11/30/2013 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. 32 11/30/2013 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 11/30/2013 Protective strategies WHIPS (Volvo) 1998. Self-aligning head restraint (SAAB) 1998. 34
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