Elderly thoracic injuries and modelling - ERNET

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18.12.04, Transport Research Injury Prevention Program, Indian Institute of Technology Delhi

Jacobo Antona-Makoshi

Japan Automobile Research Institute

Elderly thoracic injuries and modelling

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What is driving safety improvements?

Courtesy of Jason Forman

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Acchead

Forceneck

Compressionchest

ForcefemursDispknees


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Regulations:NHTSA FMVSS

ECE Type Approval

Consumer tests:NCAPs

IIHS


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Then, what is missing?

Obesity Aging

Female Population

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Ageing population

Ratio of elderly (65+) vs non-elderly (20-64) by country

Source: World Population Prospects, 2010

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Age and biomechanics transitions

Age (years)0 10 20 30 40 50 60 70 80

Pediatric Adult Advanced Age

Inju

ry k

ole

rance

Dummy risk prediction for middle aged

average size malesMusculo-skeletal development

Increase in muscle, bone size

Bone resorption, increased porosity, decreased

remodelingSarcopenia


Fragility and frailty

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Injured Body Region (Fatal, All Drivers, Frontals)

0

5

10

15

20

25

30

35

40

45

50

Head Neck Chest Abd. Spine Up.Ex.

Lo. Ex. Pelvis

Per

cent

of I

njur

ies

Age Group 1 (16-33)

Age Group 2 (34-64)

Age Group 3 (65+)

Fatal injuries in Elderly (USA)

Injured Body Region (MAIS 3+, All Drivers, Frontals)


Lo. Ex. Pelvis

Age Group 1 (16-33)

Age Group 2 (34-64)

Age Group 3 (65+)

Kent et al. 2005

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Fatal injuries in Elderly (USA)

Injured Body Region (MAIS 1+, All Drivers, Frontals)

0

5

10

15

20

25

30

35

40

45

50

Per

cent

of I

njur

ies

Age Group 1 (16-33)

Age Group 2 (34-64)

Age Group 3 (65+)

Injured Body Region (Fatal, All Drivers, Frontals)

0

5

10

15

20

25

30

35

40

45

50


Lo. Ex. Pelvis

Per

cent

of I

njur

ies

Age Group 1 (16-33)

Age Group 2 (34-64)

Age Group 3 (65+)

Kent et al. 2005

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What happens to an ageing thorax?

– Some age-related changes• Modulus and failure stress• Area, thickness of cortical bone• Costal-Cartilage• Musculature (sarcopenia)• etc

Youno Old

Stein and Granik, 1976

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Demographics in Japan 1990

Male Female

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Male Female

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Male Female

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Male Female

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Traffic crashes and deaths in Japan

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Fatalities: Elderly vs Non-elderly

Elderly fatality rates highest and increasing

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Fatality rates by Age

0

1

2

3

4

5C

asu

alty

rate

(%)

Age

Body Overall Head Face Neck

Chest Abdomen Back Hip

Arm Leg Others

Belted drivers

Chest injuries account for most deaths

IkARDA(2006-2008)

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Japanese elderly body size

US Adult AM50

Japanese Adult

Japanese Elderly

Height (cm) 175 170 160

Weight (kg) 78 68 60

Japanese elderly are particularly small

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Approach to the problem

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Japanese elderly size PMHS

Component testsTable top testsCT images

(1) Subit 2014, (2) Salzar 2014, (3) Perz 2013, (4) Subit 2014, (5) Hamzah 2013

• Rib bending (3)

• Costal cartilage shear(4)

• Muscle tensile (5)

Intact Denuded

Eviscerated (1)(2)

PMHS specimen: 71 yo, Male, 161 cm, 60ko (BMI: 22.7)

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Development of an elderly thorax FE model

Ribcage and spine Inner organs

Antona-Makoshi et al. kIP 2015

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Rib model development

model validation

Ck image

3D data of cortical bone

mesurement thickness

Element development and assignation of thicknesses

Kato et al. JSAE 2015

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Verification of rib measurement thickness

P10

P1

P2

P3

P4

P5

P6

P7

P8

P9


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Rib validation in bending


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Rib validation


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Predictability of fracture location

Rib2L Rib3L Rib4L Rib5L

Rib6L Rib9L Rib10L

Simulation Experiment

Rib7L


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Elderly thorax model assembly validation

INkACk DENUDED EVISCERAkED

kable vertical displacement (N)

kable vertical displacement (N)

Antona-Makoshi et al. JSAE 2015

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Scaling of the elderly model size to AM50

Scaling Factor 1.09 in xyz

(height based)

Antona-Makoshi et al. JSAE 2015

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Age-dependent properties implementation

Rib cortical bone fragility

Costal cartilage (fragility) Flesh properties (sarcopenia)


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Full body model validation (AM50)


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Application for restraint system research

NCAC Airbag geometry & JARI test data

Pressure: Low, Mid, High

Driver models:Adult AM50, Elderly AM50, Elderly Small

56 km/h full overlap frontal NCAP test pulse

Conventional SeatbeltForce Limit: 2, 3, 4, 5kN

Ret & Pret

Belt anchor & seat slide based on JAMA survey

data

Fixed

3 occupants x 4 belt force limits x 3 airbag settings = 36 cases

Antona-Makoshi et al. IRCOBI 2016

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Front crash simulation (Elderly AM50)

Belt Force Limit 4kN, Low Airbag Pressure


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Front crash simulation (Small Elderly)

Belt Force Limit 4kN, Low Airbag Pressure


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Chest deflection and excursionBelt force

As belt force limit ↑, excursion ↓ and chest deflection ↑

Elderly SmallAdult AM50 Elderly AM50

2 kN 3 kN 4 kN 5 kN


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Number of fractured ribs and head excursion

Adult AM50 ElderlyAM50 Elderly Small

No fractureHead strikethrough for low FL

High NFR for FL 4/5 kNNo head impact

High NFR for FL 4/5 kNHead strikethrough for low FL


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Rib fractures pattern and timing

Most rib fractures along belt path and before full contact with airbag

Elderly Small, Belt Force Limit 4kNElderly AM50, Belt Force Limit 4kN


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Effect of belt force limit

Decreasing the belt force limit from 4 kN to 3kN produced a large drop of number of fractures in the elderly but

resulted in head strikethrough

Accident data by Foret-Bruno et al. 2001, Forman et al. 2006, Mertz et al. 2007

kHOR vs HIII sled tests by Sunnevang et al. 2014

Increasing Belt Force Limit

2 kN 3 kN 4 kN 5 kN

NFR 0 NFR 8NFR 3 NFR 9

Elderly AM50, Low Airbag Pressure


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Effect of airbag pressure settings

Elderly AM50, Belt Force Limit 2kN

Increasing Airbag Pressure

Increased airbag pressure had minimal effect on chest deflections (and rib fractures) and prevented head strikethrough.

Accident data by Carrol et al. 2010

Low Mid High

NFR 0 NFR 0 NFR 0


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Summary

�Elderly are fragile and frail

�Modern cars are becoming safer for all body regions

�Elderly are under protected, particularly in the thorax

�Developed a tool for elderly thoracic safety evaluation

�Restraint systems settings optimal for young AM50 are sub-optimal for elderly, regardless of body size

�Future safety standards need to prioritize elderly, particularly in ageing countries

Thank [email protected]

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Elderly thoracic injuries and modelling - ERNET