Concussion Biomechanics and Prevention by Stefan Duma

Concussion Biomechanics and Prevention
Stefan 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 LaConte
Allison McKinnon
University of Michigan September 24, 2015

• No financial interest in any
helmet manufacturer
• No financial interest in any
sensor manufacturer
• No helmet expert witness or
consulting (NFL/NFLPA)
Financial Disclosure

Funding Sources
Toyota Motor Corporation
Toyota Central Research and Development Labs
Department of Transportation
National Highway Traffic Safety Administration
Department of Defense
US Medical Research and Material Command
National Institutes of Health
National Institute of Child Health and Human Development
National Institute of Neurological Disorders and Stroke
The Lewis Family Foundation

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 compression
Abdomen
Pelvis
Tibia
Ankle complex
Femur 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 compression
Abdomen
Pelvis
Tibia
Ankle complex
Femur loads
Accelerations
Loads
Stress/Strain
Injury Risk

Pregnant Occupant Research
0o Offset
Circ.
Longitudinal
(Medial)
Lateral
X
Y
Circ.
Longitudinal
(Medial)
Lateral
X
Y
Circ.
Longitudinal
(Medial)
Lateral
X
Y0o Offset
By Joel Stitzel, Wake Forest

Military Biomechanics Research
Head: FOCUS Headform
− Eye Modeling/Experimental
− Skull Fracture
Neck: Head Supported Mass
− Crash Pulse and Parachuting
Restraint Evaluation
− Helicopter Airbags
Chest: Lung Tissue
− Rib Fractures

Water Gun and Water Park Design

“Helmets are not the answer.”
Dr. Julian Bailes
GQ September 14, 2009
http://www.gq.com/story/nfl-players-brain-dementia-study-memory-concussions

Concussion Incidence Minimization
Rule
Changes
Proper
Technique
Better Equipment
Most
Effective
3 Strategies: • Reduce exposure to
head impact
• Rule changes
• Proper technique
+
• Reduce concussion risk
for remaining head
impacts
• Improve helmet
design
Fewest Concussions

Child Head Acceleration MeasurementData collected wirelessly for
every game and practice

Youth Football Practice Impact

First study on 7 – 8 year old football players
Average 107 impacts/player/season
29 of 38 (76%) impacts above 40g in practice
All 6 impacts over 80g in practice
Lead to Pop Warner changes

Identifying High-Risk Head Impacts
Year 1
Majority of high head acceleration
impacts occurred during practice
Pop Warner instituted new rules to
limit contact in practices
Year 2
Compared teams that adopted
new rules with teams that didn’t
Observed nearly a 50% reduction
in head impact exposure

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 Data NFL Data Volunteer DataAnimal Data
Experimental Concussion Research
1954 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 tests
• 4 embalmed cadaver heads aged 64 to 76 years old. (Lissner et al. 1960)

Wayne State Tolerance Curve
0 2 4 6 8 10 12 100
600
500
400
300
200
100
Duration (ms)
EffectiveAcceleration(g)
Exceeds Tolerance Level
Below Tolerance Level
Lissner et al. 1960
6 data points from tests
on embalmed cadaver
heads
Gurdijan et al. 1961
Comparative animal
and cadaver tests
looking at ICP
Patrick et al. 1965
Asymptote based on
non-injurious volunteer
data

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.

In Situ Brain Strain
Hardy et al (2007)
Cadaver Data
• Football helmet impacts
• Linear and Rotational Accelerations
• As accelerations increase, brain pressure
and motion increase (~7mm)

1954 Ford funds WSU
origin of WSTC
(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

1954 Ford funds WSU
origin of WSTC
(General Motors)
1971 Versace: HIC
(Ford)
1997 Mertz: scaling
2007 Hardy: brain
strain and pressure
increases.
brain pressure and
motion increase
Over 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/s2
1998 Arbogast, and
Margulies: properties
2003 Gennarelli:
concussion values
2009 Davidsson: DAI
60 60 60

Gennarelli: Rotational Acceleration and Concussion
None Mild
Concussion
Classical
Concussion
Severe
Concussion
Mild
DAI
Moderate
DAI
Severe
DAI
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
RotationalAcceleration(rad/s2)
16500
12000
8000
4500
3000
0
14500
(Gennarelli, 1985; Gennarelli, 2003)
Animal Data
60
Pure Sagittal
60
Pure Lateral
60
30 Oblique

1954 Ford funds WSU
origin of WSTC
(General Motors)
1971 Versace: HIC
(Ford)
1997 Mertz: scaling
2007 Hardy: brain
strain and pressure
increases.
brain pressure and
motion increase
from 1966 – 1983
1966 Ommaya, Hirsch
first primate tests
concussion
DAI at 16,000 r/s2
1998 Arbogast, and
2003 Gennarelli:
concussion values
2009 Davidsson: DAI
accelerations increase,
brain injury in primates
increases

1954 Ford funds WSU
origin of WSTC
(General Motors)
1971 Versace: HIC
(Ford)
1997 Mertz: scaling
2007 Hardy: brain
strain and pressure
increases.
brain pressure and
motion increase
from 1966 – 1983
1966 Ommaya, Hirsch
first primate tests
concussion
DAI at 16,000 r/s2
1998 Arbogast, and
2003 Gennarelli:
concussion values
2009 Davidsson: DAI
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)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 300 600 900 1200 1500
InjuryProbability
Linear Acceleration (m/s2)
P < 0.0001
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 2000 4000 6000 8000 10000
InjuryProbability
Angular Acceleration (rad/s2)
P < 0.0001
NFL Data

1954 Ford funds WSU
origin of WSTC
(General Motors)
1971 Versace: HIC
(Ford)
1997 Mertz: scaling
2007 Hardy: brain
strain and pressure
increases.
brain pressure and
motion increase
from 1966 – 1983
1966 Ommaya, Hirsch
first primate tests
concussion
DAI at 16,000 r/s2
1998 Arbogast, and
2003 Gennarelli:
concussion values
2009 Davidsson: DAI
increases
Mid-90s to present:
extensive research
utilizing dummy
reconstructions and
other evaluations
tests with model
Linear and rotational
accelerations are
significantly correlated
to concussion risk

1954 Ford funds WSU
origin of WSTC
(General Motors)
1971 Versace: HIC
(Ford)
1997 Mertz: scaling
2007 Hardy: brain
strain and pressure
increases.
brain pressure and
motion increase
from 1966 – 1983
1966 Ommaya, Hirsch
first primate tests
concussion
DAI at 16,000 r/s2
1998 Arbogast, and
2003 Gennarelli:
concussion values
2009 Davidsson: DAI
increases
Mid-90s to present:
extensive research
utilizing dummy
reconstructions and
other evaluations
tests with model
accelerations are
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 Instrumentation
Two parallel systems during past 10 years
Volunteer Data

0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
160,000
180,000
200,000
2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
TotalNumberofImpacts
CollectedatVirginiaTech
Cumulative HITS Data Collection
Virginia Tech Virginia Tech
North Carolina
Oklahoma
1 High School
Virginia Tech
North Carolina
Oklahoma
Dartmouth
Arizona State
5 High Schools
Virginia Tech
North Carolina
Oklahoma
Dartmouth
Brown
Minnesota
Indiana
2 High Schools
Virginia Tech
North Carolina
Oklahoma
Dartmouth
Arizona State
Illinois
Indiana
5 High Schools
Virginia Tech
North Carolina
Oklahoma
Dartmouth
Brown
Indiana
3 High Schools
Virginia Tech
North Carolina
Oklahoma
Dartmouth
Brown
Indiana
4 High Schools
Virginia Tech
North Carolina
Oklahoma
Dartmouth
Brown
Wake Forest
Indiana
4 High Schools
Virginia Tech
North Carolina
Oklahoma
Dartmouth
Brown
Wake Forest
Indiana
4 High Schools
1 Youth Team
Virginia Tech
North Carolina
Oklahoma
Dartmouth
Brown
Indiana
4 High Schools
5 Youth Teams
TeamsUsingthe
HITSystem
2,000,000+ impacts recorded at all institutions
Volunteer Data

Linear Acceleration Comparison
• Two very different methodologies, resulting
concussion values nearly identical
• Strong evidence in determination of
accelerations involving concussions
NFL Data Volunteer Data
25 Concussions
98 +/- 27 g
71 Concussions
99 +/- 31g
(Pellman, 2003; Broglio, 2010; Guskiewicz 2007, 2011; Mihalik, 2007; Rowson, 2011)

Rotational Acceleration Comparison
NFL
Volunteer
DAIConcussion
DAI

1954 Ford funds WSU
origin of WSTC
(General Motors)
1971 Versace: HIC
(Ford)
1997 Mertz: scaling
2007 Hardy: brain
strain and pressure
increases.
brain pressure and
motion increase
from 1966 – 1983
1966 Ommaya, Hirsch
first primate tests
concussion
DAI at 16,000 r/s2
1998 Arbogast, and
2003 Gennarelli:
concussion values
2009 Davidsson: DAI
increases
Mid-90s to present:
extensive research
utilizing dummy
reconstructions and
other evaluations
tests with model
accelerations are
to concussion risk
2003 – Present,
instrumented high
school and college
football players
accelerations are
to concussion risk

Lower Acceleration
Linear and Rotational
=
Lower Risk

“Helmets are not the answer.”
Dr. Julian Bailes
GQ September 14, 2009
“What helmets should we buy?”
Lester Karlin, 2009
Virginia Tech Equipment Manager
http://www.gq.com/story/nfl-players-brain-dementia-study-memory-concussions

0
200
400
600
800
1000
1200
1400
1 2
1134
416
NOCSAE Pass / Fail Threshold
Adams A2000
Severity Index
Riddell 360
0
20
40
60
80
100
120
140
160
180
200
1 2
190
84
Peak Acceleration (g)
Adams A2000 Riddell 360
Adams A2000 Riddell 360
VS
Helmet Comparison: Top Impact from 60 inch Drop Height

Automotive Safety Analogy
(NCAP) NHTSA rates safety on 5 star scale
35 mph
Fixed Barrier
38.5 mph
20 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 * rollover
Total Risk = 1 – (1 – Riskhead)*(1 – Riskneck)…
*(1 – Riskchest)*(1 – Riskfemur)

STAR Rating System for Football Helmets
STAR: Summation of Tests for the Analysis of Risk
     







4
1
6
1L H
aRhESTAR
Combines true impact exposure with an unbiased
risk analysis using real world biomechanical data
to assess helmet safety for consumers.
(Rowson and Duma, 2011)

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

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

Institute of Medicine
Committee on Sports-Related Concussions in Youth
The National Academies Press 2013
• “The 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

Linear Acceleration (g)
RotationalAcceleration(rad/s/s)
0 50 100 150 200
0
2000
4000
6000
8000
10000
Combined Linear and Rotational Risk
ROC Curves
0 0.5 1
0
0.2
0.4
0.6
0.8
1
False Positive Rate
TruePositiveRate
0 0.5 1
0
0.2
0.4
0.6
0.8
1
False Positive Rate
TruePositiveRate
NFL Data
58 Impacts
25 Concussions
0 0.5 1
0
0.2
0.4
0.6
0.8
1
False Positive Rate
TruePositiveRate
0 0.5 1
0
0.2
0.4
0.6
0.8
1
False Positive Rate
TruePositiveRate
HITS Data
63,011 Impacts
244 Concussions
Risk Contours
10%
25%
50%
75%
90%
5%
1%
𝑅𝑖𝑠𝑘 =
1
1 + 𝑒−(−10.2+0.0433𝑎+0.000873∝−0.00000092𝑎∝
AUC = 0.982
AUC = 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 fidelity”
Rank Order: Concussion – Correlate, HIC15, BRIC, BrIC

Hockey STAR
𝑆𝑇𝐴𝑅 𝐻 =
𝐿=1
4
𝑉=1
3
𝐸(𝐿, 𝑉) ∙ 𝑅(𝐴, 𝛼)
STARH: Summation of Tests for the Analysis of Risk for Hockey
• Exposure as a function of impact Location and Velocity
• Risk of concussion as a function of linear (A) and
rotational (α) headform acceleration
Hockey equation takes the same fundamental form as football:
Incidence = Exposure x Risk

Study Population
Median No. Impacts
per Player Per Season
Wilcox et al. 2014 Men’s Collegiate 287
Wilcox et al. 2014 Women’s Collegiate 170
Mihalik et al. 2012 Male Youth (13-16y) 223
Average: 227
Head Impact Exposure for Hockey
There 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

Map to Laboratory System
Pendulum Designed for Best Repeatability

Matched Impact Pulse Shapes
Instrumented Players Ice Rink Dummy Tests

32 helmets
0 5 Star
0 4 Star
1 3 Star
6 2 Star
16 1 Star
9 NR
Hockey STAR: April 2015
Not Recommended
New helmets
expected early 2016

CCM
RESISTANCE
100
BAUER
5100
RIDDELL
SPEED
FLEX
SCHUTT
AIR XP
PRO VTD
2 5
Hockey Helmets Football 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
MC10
CheckLight
Riddell Insite
X2 Patch

www.vt.edu/helmet
Consumer Information
Driving Improved Product Design

SPORT CONCUSSION
SUMMIT
September 24, 2015#uminjuryctr

Concussion Biomechanics and Prevention by Stefan Duma

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