Body Changes With Aging

University of Michigan Program for

Injury Research and Education

Automotive Safety

• Vehicles are safer than they have ever been.

• Laboratory testing using idealized occupants and standardized crashes has led to great improvements in safety.

• The body is relatively stable during early and middle adulthood - not so during early childhood or advanced age.

1

Child Small Adult

A Child’s Neck is Under-developed

2

Upper vertebrae joints are more horizontal in children:

Less resistance to translation

The Head Bone is Connected to the Neck Bone...

• Partial rupture of ligaments between bottom of skull and first vertebrae presents as bleeding in lower skull. • Total rupture of these ligaments results in rupture of the spinal cord, a fatal injury.

3

A child’s ligaments are loose to accommodate growth:

• An infant’s neck column can stretch up to 2 inches with traction.

• If stretched more than 1/4 inch, spinal cord rupture may occur.

The Head Bone is Connected tothe Neck Bone...

4

Crash Scenario

• 1994 Ford Tempo vs tree

• Driver of V1 fell asleep, V1 crosses the center line and strikes a tree on the left side of the road

• Driver and center rear passenger are the only occupants of case vehicle

• Daylight with clear weather

• Dry asphalt roadway

Crash Scene Path of Case Vehicle

5

Case Vehicle - 1994 Ford Tempo Crush Profile

CDC: 12-FYEW-3 PDOF: 360 degrees

47 cm of direct damage 77 cm of maximum crush

Impact Severity:

38 mph total delta V

all longitudinal

Case Vehicle - 1994 Ford Tempo

Center-rear passenger 18-month-old female 32 in tall, 28 lb In forward-facing child safety seat secured by manual vehicle lap belt

Photos Prior to Removal of Seat from Vehicle by Police 41-01

6

Case Vehicle - 1994 Ford Tempo Child Safety Seat

Century 3000 STE convertible child safety seat

Manufactured 12/99

CSS being used in forward-facing mode

Shoulder harness set for use in rear-facing position

Tether equipped but not used

Case Vehicle - 1994 Ford Tempo Child Safety Seat Harness Slots

Front View

7

Case Vehicle - 1994 Ford Tempo Child Safety Seat Harness Slots

Rear View

Center hit, 12 o’clock PDOF

8

9

C1C1

}

10

Result: Quadriplegia

Summary

• 18 month old, 28 lb female, front facing in CSS with improper belt placement.

• A small child’s neck is not yet fully developed and less able to withstand deforming forces.

• A heavy head and weak neck structure make small children extremely vulnerable in a frontal car crash.

• Preserving the normal structural integrity, alignment and spacing of the structures from the skull base down to the chest is critical to avoid injury to the spinal cord.

11

Observations• The optimal solution would be to provide firm support

behind the child’s head, neck and spine in a rearward-facing child seat - already done for infants.

• Spreading the crash forces in this manner prevents excessive flexion, extension and traction movements that are may result in permanent neurological disability or death.

SWEDEN - children kept rear-facing until age 3.

There is little anatomic and tissue information available regarding young children--Can imaging technology help??

Child Small Adult

12

Not all adults are the same.

13

Aging of Population

Involvement, Injury, and Fatality Rates (rates per vehicle miles of travel)

0

10

20

30

40

16-19

20-24

25-29

30-34

35-39

40-44

45-49

50-54

55-59

60-64

65-69

70-74

75-79

80-84

85+

Involvement Rate Serious Injury Rate Fatality Rate

Rate

Age Group

14

Life Span Changes in Bone Density

0

1

2

3

4

5

6

7

0 10 20 30 40 50 60 70 80

Male

Female

Age

Bo

ne

Den

sity

(ar

bit

rary

un

its)

Kraenzlin et al: McGraw-Hill, 1990 In Principles of Geriatric Medicine and Gerontology 2d ed.

Effect of Aging on Cardiac Output

0 2 4 6 8

10 12 14 16 18 20

20 40 60 80

Maximal Exercise

Rest

Car

dia

c O

utp

ut

(L/m

in)

Age M Branfronbrener, Circulation 12:557, 1955 Julius, et al: Influence of age, Circulation 36:222, 1967

15

Preexisting Diseases and Outcomes

0

5

10

15

20

25 P

erce

nt

0 1 2 > 3 Preexisting Diseases

Mortality

Milzman, et al: Pre-existing Diseases in Trauma Patients. J Trauma 32-236, 1992

Age Fragility Relationship

0

1

2

3

4

5

6

7

8

15-1

9

20-2

4

25-2

9

30-3

4

35-3

9

40-4

4

45-4

9

50-5

4

55-5

9

60-6

4

65-6

9

70-7

4

75-7

9

80-8

4

85+

Age

Fat

alit

ies

per

1,0

00 c

rash

es

Source TRB report “Transportation in an Aging Society” 1988

16

ISS Scores UM CIREN 1997 - 1998

0

10

20

30

40

50

60

70

80

0 20 40 60 80

> 60 20 - 40 Fatalities

Delta V (mph)

ISS

University of Michigan CIREN Center, 1997 - 1998

Age Incidence of Rib Fractures UM CIREN 1997 - 1998

0 10 20 30 40 50 60 70 80 90

100

< 39 40 - 59 60 - 70 > 70

University of Michigan CIREN Center, 1997 - 1998

Age

Per

cen

t

17

Injury Patterns in Elderly Fatalities CIREN (Maryland, NJ, Michigan)

Head Injury

Chest Injury (all with rib fractures)

38%

86%*

*Chest Injury a major cause of death in 71% of fatality cases

Elderly Fatalities CIREN 1997-1998

18 of 21 fatalities had Chest Injuries (86%)

All 18 had rib fractures

• 8-rib fractures

• 5-heart injuries

• 2-major vessel only

• 1-heart and major vessel

• 1-lung and major vessel

• 1-lung

18

Frontal Crash

0%

5%

10%

15%

20%

25%

30%

35%

40%

20-29 30-39 40-49 50-59 60-69 70-79

0.0%

0.2%

0.4%

0.6%

0.8%

1.0%

1.2%

1.4%

1.6%

20-29 30-39 40-49 50-59 60-69 70-79

Occupant Age Distribution

Fatality Rate by Age

NASS 1993-1996

Side Crash Cases

0%

5%

10%

15%

20%

25%

30%

35%

20-29 30-39 40-49 50-59 60-69 70-79

0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

3.0%

3.5%

4.0%

4.5%

20-29 30-39 40-49 50-59 60-69 70-79

Occupant Age Distribution

Fatality Rate by Age

1993-1996 NASS

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Frontal Crash

0%

5%

10%

15%

20%

25%

30%

35%

40%

20-29 30-39 40-49 50-59 60-69 70-79

0%

5%

10%

15%

20%

25%

30%

35%

40%

20-29 30-39 40-49 50-59 60-69 70-79

Occupant Age Distribution

Femur Fracture Rate by Age

NASS 1993-1996

Frontal Crash

0%

5%

10%

15%

20%

25%

30%

35%

40%

20-29 30-39 40-49 50-59 60-69 70-79

0%

5%

10%

15%

20%

25%

30%

35%

20-29 30-39 40-49 50-59 60-69 70-79

Occupant Age Distribution

Tibia Fracture Rate by Age

NASS 1993-1996

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Age Distribution of Rib Fracture Patterns Frontal Crashes

0%

5%

10%

15%

20%

25%

30%

20-29 30-39 40-49 50-59 60-69 70-79

Single rib > 5 ribs > 8 ribs

0%

5%

10%

15%

20%

25%

30%

35%

40%

20-29 30-39 40-49 50-59 60-69 70-79

1993-1996 NASS

Odds Ratio for Rib FracturesElderly vs. YoungNASS 1993-1996

FRONT SIDE

Single rib 3.4 4

2-3 ribs 3.8 7

> 5 ribs 13 20

21

Why??

Decreased Cortical Bone Bone Density Muscle

Increased AP diameter Cartilage ossification

ADULT ELDERLY

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7A/B • Male, 183 cm, 86 kg • Male, 183 cm, 80 kg • Age = 38 years • Age = 79 years

7A/B • Male, 183 cm, 86 kg • Male, 183 cm, 80 kg • Age = 38 years • Age = 79 years

Bone Geometry Muscle Mass/Quality

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• Male, 183 cm, 86 kg

• Age = 38 years

7A/B

• Male, 183 cm, 80 kg

• Age = 79 years

Bone DensityMuscle Mass/QualityFat Mass/Distribution

4 A/B

• Female, 168 cm, 50 kg • Female, 165 cm, 49 kg • Age = 18 years • Age = 72 years

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4 A/B

• Female, 168 cm, 50 kg • Female, 165 cm, 49 kg • Age = 18 years • Age = 72 years

Bone Density/Quality Muscle Mass/Quality

4 A/B

• Female, 168 cm, 50 kg • Female, 165 cm, 49 kg • Age = 18 years • Age = 72 years

Bone Density/Quality Muscle Mass/Quality

25

3A/B

• Female, 165 cm, 77 kg • Female, 165 cm, 78 kg

• Age = 27 years • Age = 78 years

Body Habitus

3A/B

• Female, 165 cm, 77 kg • Female, 165 cm, 78 kg

• Age = 27 years • Age = 78 years

Bone density/quality Fat distribution

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The Body Changes With Aging

• These changes affect the body’s tolerance to injurious forces.

• People at the extremes of age are particularly vulnerable to injury.

• Little is known about changes in anthropometry and body composition with aging.

• Little is known about the response of very young or very old tissues to high energy trauma.

• Development and validation of dummies representative of individuals at the extremes of age is difficult?

How many different dummies can be built and validated?

• CIREN subjects are volunteer real-life crash dummies - (living ones at that!).

• Changes in body dimensions and composition with aging affect injury tolerance.

• Injury data is being collected by computer (CT) -Body dimension and composition data also.

Can this data be used as a surrogate fortissue properties and for the determination ofbody injury tolerance?If so, what needs to be done?

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