concussion biomechanics and prevention by stefan duma
TRANSCRIPT
Biomechanical Response of the Human Head to Dynamic Impact
Concussion Biomechanics and PreventionStefan Duma, Steven Rowson, Abi Zadnik, Jaclyn Press,Bethany Rowson, Craig McNally, David Sproule, Meghan Bland, Eamon Campolettano
Brett Griesemer, Mike Goforth, Adam Viet, Kyle Staggers
Gunnar Brolinson, Mark Rogers
Stephen LaConteAllison McKinnon
University of Michigan September 24, 2015
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No financial interest in any helmet manufacturer
No financial interest in any sensor manufacturer
No helmet expert witness or consulting (NFL/NFLPA)
Financial Disclosure
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Funding SourcesToyota Motor CorporationToyota Central Research and Development Labs
Department of TransportationNational Highway Traffic Safety Administration
Department of DefenseUS Medical Research and Material Command
National Institutes of HealthNational Institute of Child Health and Human DevelopmentNational Institute of Neurological Disorders and Stroke
The Lewis Family Foundation
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1996
Automobile Analogy
Active Research in all Body Regions
We do not know 100% about everything, but know enough to make safety advances and reduce injuries.Head injury Neck injury Chest compressionAbdomenPelvisTibiaAnkle complexFemur loads
Active Research in all Body Regions
We do not know 100% about everything, but know enough to make safety advances and reduce injuries.Head injury Neck injury Chest compressionAbdomenPelvisTibiaAnkle complexFemur loads
AccelerationsLoadsStress/StrainInjury Risk
Pregnant Occupant Research
0oOffset
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Longitudinal (Medial)Lateral
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Longitudinal (Medial)Lateral
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Longitudinal (Medial)Lateral
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By Joel Stitzel, Wake Forest
Military Biomechanics Research
Head: FOCUS HeadformEye Modeling/ExperimentalSkull Fracture
Neck: Head Supported MassCrash Pulse and ParachutingRestraint EvaluationHelicopter Airbags
Chest: Lung TissueRib Fractures
Nerf Dart Design
Water Gun and Water Park Design
Nerf Sword Design
Light Saber Design
Active Research in all Body Regions
We do not know 100% about everything, but know enough to make safety advances and reduce injuries.Head injury Neck injury Chest compressionAbdomenPelvisTibiaAnkle complexFemur loads
AccelerationsLoadsStress/StrainInjury Risk
Helmets are not the answer. Dr. Julian BailesGQ September 14, 2009http://www.gq.com/story/nfl-players-brain-dementia-study-memory-concussions
Concussion Incidence Minimization
RuleChanges
ProperTechnique
Better EquipmentMostEffective3 Strategies:Reduce exposure to head impactRule changesProper technique
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Reduce concussion risk for remaining head impactsImprove helmet design
Fewest Concussions
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Child Head Acceleration Measurement
Data collected wirelessly for every game and practice
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Youth Football Practice Impact
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First study on 7 8 year old football players
Average 107 impacts/player/season29 of 38 (76%) impacts above 40g in practiceAll 6 impacts over 80g in practice
Lead to Pop Warner changes
Identifying High-Risk Head Impacts
Year 1Majority of high head acceleration impacts occurred during practice
Pop Warner instituted new rules to limit contact in practices
Year 2Compared teams that adopted new rules with teams that didnt
Observed nearly a 50% reduction in head impact exposure
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3 teams: 1 used Pop Warner Rules, 2 did not
Pop Warner Rules:Other:Other:Impacts/player/season
3 teams: 1 used Pop Warner Rules, 2 did not
Pop Warner Rules:Other:Other:Impacts/player/season
~3 million youth football players in the US
~150 impact reduction per player
~450,000,000 fewer youth head impacts per year
Is head acceleration(linear and rotational)correlated with concussion risk?
Cadaver DataNFL DataVolunteer DataAnimal DataExperimental Concussion Research1954 Ford funds WSU
1961 Gurdjian, Lissner origin of WSTC
1966 Gadd: GSI or SI (General Motors)
1971 Versace: HIC (Ford)
1997 Mertz: scaling
2007 Hardy: brain strain and pressure
Human Tolerance to Head Acceleration
Wayne State Tolerance Curve (WSTC)Correlated peak acceleration to skull fracture for impacts of durations between 1 and 6 ms Derived from 6 data points out of 23 tests4 embalmed cadaver heads aged 64 to 76 years old. (Lissner et al. 1960)
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Wayne State Tolerance Curve
0 2 4 6 8 10 12 100600
500
400
300
200
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Duration (ms)Effective Acceleration (g)Exceeds Tolerance LevelBelow Tolerance Level
Lissner et al. 19606 data points from testson embalmed cadaverheads
Gurdijan et al. 1961Comparative animaland cadaver testslooking at ICP
Patrick et al. 1965Asymptote based onnon-injurious volunteerdata
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Injury Metrics Derived from WSTC
Severity Index (SI)
Weighted impulse criterion based on a linear approximation (slope = -2.5) of the WSTC plotted on a log-log scale. (Gadd 1966)
Slope indicates a greater dependence of injury on the loading intensity, as opposed to loading duration
Suggested a threshold of 1500 for distributed loading (Gadd 1971)
Head Injury Criterion (HIC)
Developed from a mathematical review of the relationship between SI and WSTC(Versace 1971)
Able to account for high tolerance of long duration, low magnitude accelerations
In 1972, NHTSA replaced SI with HIC in FMVSS 208, setting a threshold of 1000(Gadd 1966)In 1970, NOCSAE implemented an SI < 1500 standard for football helmets. A 50% reduction in fatalities was observed in 1971.In 1996, NOCSAE lowered the SI threshold to 1200 to better reflect the auto safety regulation that HIC be less than 1000.
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In Situ Brain StrainHardy et al (2007)
Cadaver DataFootball helmet impactsLinear and Rotational AccelerationsAs accelerations increase, brain pressure and motion increase (~7mm)
28Aligned, linear test with helmetHard to control impact parameters independently.Head can still rotate in helmet, so not pure linear acc.
Cadaver DataNFL DataVolunteer DataAnimal DataExperimental Concussion Research1954 Ford funds WSU
1961 Gurdjian, Lissner origin of WSTC
1966 Gadd: GSI or SI (General Motors)
1971 Versace: HIC (Ford)
1997 Mertz: scaling
2007 Hardy: brain strain and pressure
As linear acceleration increases, risk of injury increases.
As linear and rotational acceleration increase, brain pressure and motion increase
Cadaver DataNFL DataVolunteer DataAnimal DataExperimental Concussion Research1954 Ford funds WSU
1961 Gurdjian, Lissner origin of WSTC
1966 Gadd: GSI or SI (General Motors)
1971 Versace: HIC (Ford)
1997 Mertz: scaling
2007 Hardy: brain strain and pressure
As linear acceleration increases, risk of injury increases.
As linear and rotational acceleration increase, brain pressure and motion increaseOver 200 Primate tests performed in six sets from 1966 1983
1966 Ommaya, Hirsch first primate tests
More recent analysis:1985 Ommaya:4500r/s2 concussion 1992 Margulies,Thibault DAI at 16,000 r/s21998 Arbogast, and Margulies: properties2003 Gennarelli: concussion values2009 Davidsson: DAI
Gennarelli: Rotational Acceleration and ConcussionNoneMild ConcussionClassical ConcussionSevere ConcussionMild DAIModerate DAISevere DAI1650012000800045003000014500
(Gennarelli, 1985; Gennarelli, 2003)Animal Data
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Cadaver DataNFL DataVolunteer DataAnimal DataExperimental Concussion Research1954 Ford funds WSU
1961 Gurdjian, Lissner origin of WSTC
1966 Gadd: GSI or SI (General Motors)
1971 Versace: HIC (Ford)
1997 Mertz: scaling
2007 Hardy: brain strain and pressure
As linear acceleration increases, risk of injury increases.
As linear and rotational acceleration increase, brain pressure and motion increaseOver 200 Primate tests performed in six sets from 1966 1983
1966 Ommaya, Hirsch first primate tests
More recent analysis:1985 Ommaya:4500r/s2 concussion 1992 Margulies,Thibault DAI at 16,000 r/s21998 Arbogast, and Margulies: properties2003 Gennarelli: concussion values2009 Davidsson: DAI
As linear and rotational accelerations increase, brain injury in primates increases
Cadaver DataNFL DataVolunteer DataAnimal DataExperimental Concussion Research1954 Ford funds WSU
1961 Gurdjian, Lissner origin of WSTC
1966 Gadd: GSI or SI (General Motors)
1971 Versace: HIC (Ford)
1997 Mertz: scaling
2007 Hardy: brain strain and pressure
As linear acceleration increases, risk of injury increases.
As linear and rotational acceleration increase, brain pressure and motion increaseOver 200 Primate tests performed in six sets from 1966 1983
1966 Ommaya, Hirsch first primate tests
More recent analysis:1985 Ommaya:4500r/s2 concussion 1992 Margulies,Thibault DAI at 16,000 r/s21998 Arbogast, and Margulies: properties2003 Gennarelli: concussion values2009 Davidsson: DAI
As linear and rotational accelerations increase, brain injury in primates increases
Mid-90s to present:extensive research utilizing dummy reconstructions and other evaluations
2003: Pellman, Viano HIII reconstructions
2003: King, analysis of tests with model
King: Linear and Rotational Acceleration 53 NFL Cases: 22 injury and 31 Non-injury(King, 2003)
NFL Data
Cadaver DataNFL DataVolunteer DataAnimal DataExperimental Concussion Research1954 Ford funds WSU
1961 Gurdjian, Lissner origin of WSTC
1966 Gadd: GSI or SI (General Motors)
1971 Versace: HIC (Ford)
1997 Mertz: scaling
2007 Hardy: brain strain and pressure
As linear acceleration increases, risk of injury increases.
As linear and rotational acceleration increase, brain pressure and motion increaseOver 200 Primate tests performed in six sets from 1966 1983
1966 Ommaya, Hirsch first primate tests
More recent analysis:1985 Ommaya:4500r/s2 concussion 1992 Margulies,Thibault DAI at 16,000 r/s21998 Arbogast, and Margulies: properties2003 Gennarelli: concussion values2009 Davidsson: DAI
As linear and rotational accelerations increase, brain injury in primates increases
Mid-90s to present:extensive research utilizing dummy reconstructions and other evaluations
2003: Pellman, Viano HIII reconstructions
2003: King, analysis of tests with model
Linear and rotational accelerations are significantly correlated to concussion risk
Cadaver DataNFL DataVolunteer DataAnimal DataExperimental Concussion Research1954 Ford funds WSU
1961 Gurdjian, Lissner origin of WSTC
1966 Gadd: GSI or SI (General Motors)
1971 Versace: HIC (Ford)
1997 Mertz: scaling
2007 Hardy: brain strain and pressure
As linear acceleration increases, risk of injury increases.
As linear and rotational acceleration increase, brain pressure and motion increaseOver 200 Primate tests performed in six sets from 1966 1983
1966 Ommaya, Hirsch first primate tests
More recent analysis:1985 Ommaya:4500r/s2 concussion 1992 Margulies,Thibault DAI at 16,000 r/s21998 Arbogast, and Margulies: properties2003 Gennarelli: concussion values2009 Davidsson: DAI
As linear and rotational accelerations increase, brain injury in primates increases
Mid-90s to present:extensive research utilizing dummy reconstructions and other evaluations
2003: Pellman, Viano HIII reconstructions
2003: King, analysis of tests with model
Linear and rotational accelerations are significantly correlated to concussion risk
2003 Present, instrumented high school and college football players
HIT System
6 Accelerometers mounted normal to the skull
3 Linear and Resultant Rotational Accelerations
~$1,000/helmet
Validated by NFL, others
6DOF Device (VT)
12 Accelerometers mounted tangential
3 Linear and 3 Rotational Accelerations (6DOF)
~$10,000/helmet
Validates HIT System
Helmet InstrumentationTwo parallel systems during past 10 years
Volunteer Data
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Cumulative HITS Data Collection
Virginia TechVirginia TechNorth CarolinaOklahoma1 High SchoolVirginia TechNorth CarolinaOklahomaDartmouthArizona State5 High SchoolsVirginia TechNorth CarolinaOklahomaDartmouthBrownMinnesotaIndiana2 High SchoolsVirginia TechNorth CarolinaOklahomaDartmouthArizona StateIllinoisIndiana5 High SchoolsVirginia TechNorth CarolinaOklahomaDartmouthBrownIndiana3 High SchoolsVirginia TechNorth CarolinaOklahomaDartmouthBrownIndiana4 High SchoolsVirginia TechNorth CarolinaOklahomaDartmouthBrownWake ForestIndiana4 High SchoolsVirginia TechNorth CarolinaOklahomaDartmouthBrownWake ForestIndiana4 High Schools1 Youth TeamVirginia TechNorth CarolinaOklahomaDartmouthBrownIndiana4 High Schools5 Youth TeamsTeams Using theHIT System2,000,000+ impacts recorded at all institutionsVolunteer Data
Linear Acceleration ComparisonTwo very different methodologies, resulting concussion values nearly identical
Strong evidence in determination of accelerations involving concussionsNFL DataVolunteer Data25 Concussions
98 +/- 27 g71 Concussions
99 +/- 31g(Pellman, 2003; Broglio, 2010; Guskiewicz 2007, 2011; Mihalik, 2007; Rowson, 2011)
Rotational Acceleration Comparison
NFLVolunteerDAIConcussionDAI
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Cadaver DataNFL DataVolunteer DataAnimal DataExperimental Concussion Research1954 Ford funds WSU
1961 Gurdjian, Lissner origin of WSTC
1966 Gadd: GSI or SI (General Motors)
1971 Versace: HIC (Ford)
1997 Mertz: scaling
2007 Hardy: brain strain and pressure
As linear acceleration increases, risk of injury increases.
As linear and rotational acceleration increase, brain pressure and motion increaseOver 200 Primate tests performed in six sets from 1966 1983
1966 Ommaya, Hirsch first primate tests
More recent analysis:1985 Ommaya:4500r/s2 concussion 1992 Margulies,Thibault DAI at 16,000 r/s21998 Arbogast, and Margulies: properties2003 Gennarelli: concussion values2009 Davidsson: DAI
As linear and rotational accelerations increase, brain injury in primates increases
Mid-90s to present:extensive research utilizing dummy reconstructions and other evaluations
2003: Pellman, Viano HIII reconstructions
2003: King, analysis of tests with model
Linear and rotational accelerations are significantly correlated to concussion risk
2003 Present, instrumented high school and college football players
Linear and rotational accelerations are significantly correlated to concussion risk
Lower AccelerationLinear and Rotational=Lower Risk
Helmets are not the answer. Dr. Julian BailesGQ September 14, 2009
What helmets should we buy?Lester Karlin, 2009Virginia Tech Equipment Managerhttp://www.gq.com/story/nfl-players-brain-dementia-study-memory-concussions
1134416NOCSAE Pass / Fail ThresholdAdams A2000Severity IndexRiddell 360
19084Peak Acceleration (g)Adams A2000Riddell 360
Adams A2000
Riddell 360VSHelmet Comparison: Top Impact from 60 inch Drop Height
Automotive Safety Analogy(NCAP) NHTSA rates safety on 5 star scale
35 mphFixed Barrier
MDB
38.5 mph20 mph
Injury risk to the head, neck, chest, and femur are considered for frontal and side tests (rollover is ratio calculation)
A total injury risk for each testing configuration is computed
Each overall injury risk is weighted based on exposure and summed to compute overall risk
Overall risk = 5/12 * frontal + 4/12 * side + 3/12 * rolloverTotal Risk = 1 (1 Riskhead)*(1 Riskneck) *(1 Riskchest)*(1 Riskfemur)
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STAR Rating System for Football HelmetsSTAR: Summation of Tests for the Analysis of Risk
Combines true impact exposure with an unbiased risk analysis using real world biomechanical data to assess helmet safety for consumers.(Rowson and Duma, 2011)
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www.vt.edu/helmet
2015: 12+ 5-Star Helmets (rolling additions)
www.vt.edu/helmet
Journal of Neurosurgery 2014
Data compiled from 8 collegiate football teams
1833 players over 6 years
Exposure controlled
Clinical Evidence
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Riddell Revolution reduces risk of concussion by 53.9% compared to Riddell VSR4 (p=0.03)
(STAR Equation predicts 54.2% reduction)Journal of Neurosurgery 2014
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Institute of MedicineCommittee on Sports-Related Concussions in YouthThe National Academies Press 2013The STAR system is theoretically grounded and represents an intriguing approach to how the injury mitigation properties of a helmet could be assessed.
The STAR system is based on sound principles
Adding rotational acceleration would increase application of the STAR system
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Combined Linear and Rotational RiskROC Curves
NFL Data58 Impacts25 Concussions
HITS Data63,011 Impacts244 ConcussionsRisk Contours10%25%50%75%90%5%1%AUC = 0.982AUC = 0.892(Rowson and Duma, ABME, 2013)Volunteer Data
SAE Congress, 2015
Concussion Correlate: Combined Risk Function (Rowson and Duma 2013)Concussion Correlate curve demonstrated the best fidelityRank Order: Concussion Correlate, HIC15, BRIC, BrIC
Hockey STAR
STARH: Summation of Tests for the Analysis of Risk for HockeyExposure as a function of impact Location and Velocity
Risk of concussion as a function of linear (A) and rotational () headform acceleration
Hockey equation takes the same fundamental form as football:
Incidence = Exposure x Risk
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StudyPopulationMedian No. Impacts per Player Per SeasonWilcox et al. 2014Mens Collegiate287Wilcox et al. 2014Womens Collegiate170Mihalik et al. 2012Male Youth (13-16y)223Average:227
Head Impact Exposure for HockeyThere are number of published studies on head impact exposure sustained by male and female hockey players
In-Rink Head Impact Response
Rented an ice rink to characterize the head impact response resulting from board, glass, and ice impacts
Can be used to assure lab testing best replicates real-world head impacts
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Map to Laboratory SystemPendulum Designed for Best Repeatability
Matched Impact Pulse ShapesInstrumented PlayersIce Rink Dummy Tests
32 helmets0 5 Star0 4 Star1 3 Star6 2 Star16 1 Star9 NR
Hockey STAR: April 2015Not RecommendedNew helmets expected early 2016
CCMRESISTANCE 100BAUER5100RIDDELLSPEED FLEXSCHUTTAIR XP PRO VTD
2
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Hockey HelmetsFootball Helmets
Head: 0.7 in (18 mm) Shoulders: 1.2 in (30 mm) Elbows: 1.5 in (38 mm) Wrist: 1.5 in (38 mm) Hips: 1.5 in (38 mm) Knees: 2.2 in (56 mm) Shins: 1.6 in (41 mm) Padding Thickness(Bauer 5100 helmet and Bauer Nexus padding)
New Sensors New Opportunities
Triax
MC10CheckLightRiddell Insite
X2 Patch
www.vt.edu/helmetConsumer InformationDriving Improved Product Design
Concussion Biomechanics and PreventionStefan Duma, Steven Rowson, Abi Zadnik, Jaclyn Press,Bethany Rowson, Craig McNally, David Sproule, Meghan Bland, Eamon Campolettano
Brett Griesemer, Mike Goforth, Adam Viet, Kyle Staggers
Gunnar Brolinson, Mark Rogers
Stephen LaConteAllison McKinnon
University of Michigan September 24, 2015
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SPORT CONCUSSION SUMMIT September 24, 2015
#uminjuryctr