Concussion Biomechanics and Prevention by Stefan Duma

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



AccelerationsLoadsStress/StrainInjury Risk

Pregnant Occupant Research

0oOffset

Circ.

Longitudinal (Medial)Lateral

XY

Circ.


XY

Circ.


XY0oOffset

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



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.





1997 Mertz: scaling


As linear acceleration increases, risk of injury increases.

As linear and rotational acceleration increase, brain pressure and motion increase





1997 Mertz: scaling



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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1997 Mertz: scaling






As linear and rotational accelerations increase, brain injury in primates increases





1997 Mertz: scaling







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





1997 Mertz: scaling










Linear and rotational accelerations are significantly correlated to concussion risk





1997 Mertz: scaling











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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1997 Mertz: scaling











2003 Present, instrumented high school and college football players


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

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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

Health & Medicine

Concussion Biomechanics and Prevention by Stefan Duma