DECELERATION VELOCITY AND ENERGY … · car vs car (n=147) car vs SUVT (n=75) car vs nonvehicle...

DECELERATION VELOCITY AND ENERGY DISSIPATION ON IMPACT IN MOTOR VEHICLE CRASHES: KEY FACTORS IN THE PRODUCTION OF THE PATTERN OF INJURIES AND PATIENT SURVIVAL AS A FUNCTION OF THE DIRECTION

OF CRASH, WITH SPECIAL REFERENCE TO THORACIC AORTIC INJURIES.

A CRASH INJURY RESEARCH ENGINEERING NETWORK (CIREN) STUDY

J. H. SIEGEL, MD; J.A. SMITH, MS; S.Q. SIDDIQI, MD: NEW JERSEY MEDICAL SCHOOL: UMDNJ CIREN CENTER,

NEWARK, NEW JERSEY

IN ADDITION TO THE NJ CIREN CENTER, DATA INCLUDED WAS COLLECTED BY 9 OTHER CIREN CENTER PRINCIPAL INVESTIGATORS:

1) J.S. Augenstein, MD & K.E. Digges, PhD: Lehman Injury Research Center, University of Miami, Miami, FL2) P.C. Dischinger, PhD, A.R. Burgess, M.D., & J.O’Connor, M.D. National Study Center for Trauma & EMS, University of Maryland, Baltimore, Md.3) A.B. Eastman, M.D., D.B. Hoyt, M.D., & G. Cooper, Scripps Memorial Hospital & University of California San Diego & San Diego County Trauma System, San Diego, CA4) M. Eichelberger, M.D., Children’s Medical Center, Washington, DC 5) S.M. Fakhry, M.D., & D.D. Watts, PhD., Fairfax Hospital – Honda Inova Center, Falls Church, VA 6) T.A. Gennarelli, M.D., Froedtert Hospital & Medical College of Wisconsin, Milwaukee, WI7) D. Grossman, M.D., C. Mock, M.D., F. Rivara, M.D., Harborview Injury Prevention & Research Center, University of Washington, Seattle, WA8) L.W. Rue III, M. D., Mercedes-Benz Center: University of Alabama Health System, Birmingham. AL9) S.C. Wang, M.D., & L. Schneider, PhD., University of Michigan Health System & University of Michigan Transportation Research Institute, Ann Arbor, MI

MATERIALS & METHODS I

CIREN DATA FROM 876 ADULT DRIVERS OR FRONT-SEAT OCCUPANTS OF MOTOR VEHICLE CRASHES (MVCs) INVOLVING CARS; OR SPORT UTILITY, VANS, OR LIGHT PICK-UP TRUCKS (SUVT). CRASHES WITH FULL ROLLOVERS, REAR-END COLLISIONS, OR EJECTED PATIENTS EXCLUDED. NO SIDE AIRBAGS IN SERIES. DATA SPAN PERIOD 1996-2002.

552 FRONTAL MVCs (PDOF 340º - 0 - 20º).334 LATERAL MVCs (PDOF <340º-190º OR >20º-170º). INCLUDES 46 FRONTAL MVC AORTIC INJURY (AI) AND 34 LATERAL MVC AI CASES.

2 24 18

100

15 17 213

65 73

452

52 3013

0

50

100

150

200

250

300

350

400

450

500

550

600

200-259 260-299 300-339 frontal (340-20)

21-60 61-100 101-160

PDOF

nu

mb

er o

f cas

es

fatalities survivors

driver side passenger side

frontal

laterallateral

MATERIALS & METHODS II

PATIENT:1) AGE, SEX, HEIGHT & WEIGHT2) DIRECTION OF CRASH FMVC OR LMVC3) OCCUPANT VEHICLE (V1) VS OTHER VEHICLE (V2) OR NON VEHICLE (FO)4) SEAT-BELT AND AIRBAG DEPLOYMENT5) SURVIVAL OR DEATH STATUS6) PATIENT OR NEXT OF KIN INFORMED CONSENT OR 7) MEDICAL EXAMINERS AUTHORITY FOR SCENE FATAL CRASHES8) POLICE, EMS & HOSPITAL RECORDS9) MEDICAL EXAMINER AUTOPSY REPORTS10) PSYCHOSOCIAL EVALUATION IN HOSPITAL & FOLLOW-UP AT 6, 12 & 18 MONTHS

MATERIALS & METHODS III

VEHICLE:CRASH RECONSTRUCTION DATA FOR MECHANISM OF CRASH WITH SCENE DIAGRAM AND DETERMINATION OF PRIMARY DIRECTION OF FORCE (PDOF) ON SUBJECT VEHICLE (V1)DELINEATION OF SITES OF DRIVER AND/OR FRONT-SEAT PATIENT’S INJURY PRODUCING CONTACT WITH PASSENGER COMPARTMENT STRUCTURESCOMPUTATION OF IMPACT DECELERATION VELOCITY (DELTA V) ON V1 VEHICLECOMPUTATION OF IMPACT ENERGY DISSIPATION (IE) ON V1 VEHICLE

AGE DISTRIBUTION OF ALL CASES

16 13 13 13 7 9 6 2 1

209

141 138

106

8856

48

1000

50

100

150

200

250

15-24 25-34 35-44 45-54 55-64 65-74 75-84 85-94 95-104

age range

freq

uen

cy

aorta non-aorta

AGE DISTRIBUTION OF ALL AORTA CASES

8

109

10

45

21 1

61

1

1

32

2

10

2

23

2

0

2

2

0

0

0

2

4

6

8

10

12

14

16

18

15-24 25-34 35-44 45-54 55-64 65-74 75-84 85-94 95-104

age range

freq

uen

cy

ME HD S

Frontal cases with complete data from CIREN databaseby fatality (N=552)

y = 32.218x2 + 2925.8x - 59451R2 = 0.4126

0

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1000000

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0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Delta V (kph)

ener

gy d

issi

pate

d (jo

ules

)

lived (n=452) died (n=100)

C:/crash/CIRENSQL/CIRENgraphfrtrestr1.xls11-08-2003

= median (46 kph)= mean (48.0 ±19.7 kph)

Lateral cases with complete data from CIREN databaseby fatality (N=324)

y = 53.209x2 + 649.66x + 736.67R2 = 0.8125

0

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0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Delta V (kph)

ener

gy d

issi

pate

d (jo

ules

)

lived (n=246) died (n=78)

C:/crash/CIRENSQL/CIRENgraphlatrestr1.xls 11-08-03


SUMMARY & CONCLUSIONS I

COMPUTED CRASH DELTA Vs

1. Frontal Motor Vehicle Crash : MEDIAN MEAN & SD SEMN=552 46 KPH 48 ± 19.7 KPH 0.84 KPH

2. Lateral Motor Vehicle Crash: MEDIAN MEAN & SD SEMN=324 33 KPH 36 ± 16.4 KPH 0.91 KPH

NHTSA Frontal Motor Vehicle Crash Test:FIXED BARRIER OR OFF-SET AT 48 KPH

NHTSA Lateral Motor Vehicle Crash Test:MOVING 27º CRABBED BARRIER AT 56 KPH, RELATION TO ACTUAL DELTA V NOT DEFINED BY MEASUREMENT AT SITE OF IMPACT ON SUBJECT VEHICLE, BUT APPEARS TO BE 20 -25 MPH (32 – 40 KPH)

SUMMARY & CONCLUSIONS II

3. TO EXPLAIN SOME OF THE FACTORS INVOLVED IN THESE ISSUES, THE RELATIONSHIP OF THE IMPACT ENERGY (IE) DISSIPATED ON V1 AS A FUNCTION OF THE DECELERATION VELOCITY ON IMPACT (DELTA V) WAS EXAMINED IN FMVC VS LMVC.

4. IN BOTH FMVC AND LMVS THE RELATION BETWEEN IE AND DELTA V WAS SHOWN TO BE EXPONENTIAL, WITH THE MAJOR INCREASE IN IE FOR A GIVEN DELTA V SEEN TO BEGIN AT DELTA Vs GREATER THAN THE MEAN, 48 KPH FOR FMVC AND 36 KPH FOR LMVC.

Frontal cases with complete data from CIREN databaseby type of V2 where V1=car (N=405)

y = 265.64x2 - 16386x + 299156R2 = 0.3285V2=SUVT

y = -0.1971x2 + 4220.3x - 67111R2 = 0.6349

V2=car

y = 44.36x2 + 1097.3x - 21152R2 = 0.8771

V2=nonvehicle

0

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0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Delta V (kph)

ener

gy d

issi

pate

d (jo

ules

)

V1=car, V2=SUVT (n=75) V1=car, V2=non-vehicle (n=178) V1=car, V2=car (n=147)

C:/crash/CIRENSQL/CIRENgraphfrtrestr1.xls11-08-2003

slope p<0.05


All sedan vs sedan cases with complete data from CIREN databaseFrontal vs Lateral regressions

y = 47.461x2 + 834.38x - 5183.7R2 = 0.8414

lateralN=108

y = -0.1971x2 + 4220.3x - 67111R2 = 0.6349

frontalN=147

0

100000

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0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Delta V (kph)

ener

gy d

issi

pate

d (jo

ules

)

lateral sedan vs sedan frontal sedan vs sedan


slope p<0.05

SUMMARY & CONCLUSIONS III

5. MOREOVER, FOR ALL CAR VS CAR MOTOR VEHICLE CRASHES (MVCs) , WHEN THE REGRESSIONS FOR IE VS DELTA V ARE COMPARED, THE RATE OF INCREASE IN IE PER UNIT RISE IN DELTA V IS SIGNIFICANTLY GREATER (P<0.05) IN LMVC COMPARED TO FMVC, BECOMING MOST PROMINENT ABOVE DELTA V > 56 KPH (35 MPH).

6. IN FMVC, WHEN THE IE/DELTA V RELATION FOR CARS (V1) STRUCK BY AN SUVT IS COMPARED TO THAT OF CARS (V1) STRUCK BY ANOTHER CAR, OR CARS STRIKING A FIXED OBJECT IT WAS FOUND THAT THE RISE IN IE FOR CARS IMPACTING A FIXED OBJECT WAS SIGNIFICANTLY GREATER (P<0.05) THAN THAT FOR CARS VS CARS, AND FOR CARS STRUCK BY AN SUVT WAS ALSO GREATER (P=0.052, NS) COMPARED TO THAT SEEN WHEN A CAR (V1) STRUCK ANOTHER CAR.

Percent Mortality for Frontal Crashes

10

32

9

15

24

29 28 27

16

31

1920

0

10

20

30

40

50

60

car vs car (n=147) car vs SUVT (n=75) car vs nonvehicle (n=178) all crashes where V1=car(n=405)

per

cen

t mo

rtal

ity

<=48 kph >48 kph overall C:/crash/CIRENSQL/CIRENgraphfrtrestr1.xlsas of 11-08-2003

***

**

* = p<0.05 vs <=48 kph ** = p<0.01 vs <=48 kph++ = p<0.01 vs car vs SUVT at <=48 kph

++ ++

Percent Mortality for Lateral Crashes

10

15

26

16

38

43

36

39

19

27

30

25

0

10

20

30

40

50

60

car vs car (n=108) car vs SUVT (n=85) car vs nonvehicle (n=82) all crashes where V1=car(n=279)

per

cen

t mo

rtal

ity

<=36 kph >36 kph overall C:/crash/CIRENSQL/CIRENgraphlatrestr1.xlsas of 11-10-2003

** = p<0.01 vs <=36 kph+ = p<0.05 vs car vs car at <=36 kph

**

****NS

+

Frontal cases with complete data from CIREN databaseby fatality and restraint use (N=552)

y = 32.218x2 + 2925.8x - 59451R2 = 0.4126

0

100000

200000

300000

400000

500000

600000

700000

800000

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1000000

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0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Delta V (kph)

ener

gy d

issi

pate

d (jo

ules

)

no SB, no AB, died (n=12) no SB, no AB, survived (n=14) SB no AB, died (n=10)SB no AB, survived (n=60) AB no SB, died (n=48) AB no SB, survived (n=154)AB+SB, died (n=28) AB+SB, survived (n=224) AB, SB undetermined (n=2)

C:/crash/CIRENSQL/CIRENgraphfrtrestr1.xls 11-08-03


Lateral cases with complete data from CIREN databaseby fatality and restraint use (N=324)

y = 53.209x2 + 649.66x + 736.67R2 = 0.8125

0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1000000

1100000

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Delta V (kph)

ener

gy d

issi

pate

d (jo

ules

)

no SB, no AB, died (n=14) no SB, no AB, survived (n=23) SB no AB, died (n=24)SB no AB, survived (n=91) AB no SB, died (n=23) AB no SB, survived (n=39)AB+SB, died (n=17) AB+SB, survived (n=93)



MORTALITY BY TYPE OF RESTRAINT:FOR V1 OCCUPANT IN ALL 876 Motor Vehicle Crashes

552 FMVC % M 324 LMVC %MTOTAL 18.1% TOTAL 24.1%

W NONE 46.2%**++# NONE 37.8%**+ W2º SB ONLY 14.3% SB ONLY 20.9% 2º3º AB ONLY 23.8%** AB ONLY 37.1%**+ W1º AB+SB 11.1% AB+SB 15.5% 1º

** = p<0.01 vs AB+SB+ = p<0.05 vs SB only

# = p<0.05 vs AB only++ = p<0.01 vs SB only

SUMMARY & CONCLUSIONS IV

7. FMVC MORTALITY= 48 KPH > 48 KPH

CAR VS CAR 10% 24% *CAR VS FIXED OBJECT 9% 28% **CAR VS SUVT 32%++ 29%

LMVC MORTALITY= 36 KPH > 36 KPH

CAR VS CAR 10% 38%**CAR VS FIXED OBJECT 26%+ 36%CAR VS SUVT 15% 43%**

CAR VS OTHER AT = MEAN DELTA V (+ P<0.05, ++ P<0.01)CAR VS OTHER AT = VS > MEAN DELTA V (* P<0.05, ** P<0.01)

Aorta cases with complete data and outcome indicated (N=46)Frontal only

y = 32.218x2 + 2925.8x - 59451R2 = 0.4126

p<0.001

0

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300000

400000

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600000

700000

800000

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1000000

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0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Delta V (kph)

ener

gy d

issi

pate

d (jo

ules

)

aorta hospital deaths (n=10) aorta scene deaths (n=30) aorta survivors (n=6)


Aorta cases with complete data and outcome indicated (N=34)Lateral only

y = 53.209x2 + 649.66x + 736.67R2 = 0.8125

p<0.001

0

100000

200000

300000

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1000000

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0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Delta V (kph)

ener

gy d

issi

pate

d (jo

ules

)

aorta hospital deaths (n=7) aorta scene deaths (n=20) aorta survivors (n=7)


SUMMARY & CONCLUSIONS V

8. IN FMVCs 46% OF THE CRASHES, BUT 58% OF THE DEATHS OCCURRED AT DELTA Vs ABOVE THE MEAN OF 48 KPH WHICH APPROXIMATES THE 48 KPH OF THE FEDERAL CRASH TEST STANDARD. HOWEVER, 63% OF THE FMVC AIs AND 60% OF THE FMVC AI DEATHS OCCURRED ABOVE THE MEAN DELTA V, WITH IE = 155,524 JOULES RESULTING IN = 77 CM MAXIMUM FRONTAL DEFORMATION.

9. IN LMVCs 40% OF THE CRASHES, BUT 64% OF THE DEATHS OCCURRED AT DELTA Vs ABOVE THE MEAN OF 36 KPH. HOWEVER, 64% OF THE LMVC AIs AND 65% OF THE LMVC AI DEATHS OCCURRED ABOVE THE MEAN DELTA V, WITH IE = 92,956 JOULES RESULTING IN = 63 CM MAXIMUM LATERAL DEFORMATION.

SUMMARY & CONCLUSIONS VI

10. OF THE 80 AORTIC INJURIES (AI), 63% WERE DEAD AT THE SCENE (ME), 21% DIED AFTER REACHING THE HOSPITAL (HD) AND 16% SURVIVED (S) TO LEAVE THE HOSPITAL ALIVE.

11. THE ASCENDING AORTA WAS THE PRIMARY SITE OF AIIN 13.2%, THE AORTIC ARCH IN 2.6%, THE AORTIC ISTHMUS IN 75% AND THE DESCENDING THORACIC AORTA IN 7.9% OF THE TOTAL AI CASES.

12. ALL BUT ONE OF THE SURVIVORS HAD THEIR AI AT THE ISTHMUS OR IN THE PROXIMAL DESCENDING AORTA

360/0

270

180

90

Principal Direction of Force (PDOF) for Aorta Injury Cases

315

135

45

225

3015

60

75

150

105

120

195 165210

240

255

285

300

330345

P

I

P = proximal A = arch I = isthmusD = desc. thor.

By site of aortic lesion6 cases had lesions in multiple locations (shown in red)

I

D

I

II I

P

I

I

I

I

I

I

P

II

P

I

I

I

I

I

I

PD

I

I

I

D

I

PD

I

II I

D

I

P

I

I

ID

ID

I

PI

I

I

I

I IP

D

II

I

II

I

I

I

I

PI

PII

D

I

I

A

A

I

I

I

I

I

I

Frontal

SUMMARY & CONCLUSIONS VII

13 IN 76 OF THE 80 AORTIC INJURY CASES, THE SITE OF THE LESION AND THE PRINCIPAL DIRECTION OF FORCE (PDOF) COULD BE IDENTIFIED.

14. AS DEFINED BY PDOF (340º-0 0-20º) ALL BUT ONE OF THE 11 PROXIMAL AORTIC INJURIES OCCURRED IN FRONTAL MOTOR VEHICLE CRASHES (FMVC)s, 1 PRIMARY AORTIC ARCH, 27 PRIMARY AND 6 SECONDARY ISTHMUS TEARS AND 5 PRIMARY AND 1 SECONDARY TEAR OF THE DESCENDING AORTA ALSO RESULTED FROM FMVCs.

15. IN LMVC AIs, THERE WERE 30 PRIMARY ISTHMUS, 1 PRIMARY DESCENDING AORTA, 1 PROXIMAL AORTA TEAR & 1 AORTIC ARCH LACERATION.

Aorta cases (frontal) with complete data from CIREN databaseby fatality and restraint use (N=46)

y = 32.218x2 + 2925.8x - 59451R2 = 0.4126

0

100000

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0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Delta V (kph)

ener

gy d

issi

pate

d (jo

ules

)

no SB, no AB, ME (n=7) no SB, no AB, HD (n=2) no SB, no AB, survived (n=2)SB no AB, ME (n=1) SB no AB, HD (n=1) AB no SB, ME (n=15)AB no SB, HD (n=4) AB no SB, survived (n=2) AB+SB, ME (n=5)AB+SB, HD (n=3) AB+SB, survived (n=2) restraint use UTBD, ME (n=2)

C:/crash/CIRENSQL/CIRENgraphfrtrestr1.xls 11-08-03


Aorta cases (lateral) with complete data from CIREN databaseby fatality and restraint use (N=34)

y = 53.209x2 + 649.66x + 736.67R2 = 0.8125

0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1000000

1100000

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Delta V (kph)

ener

gy d

issi

pate

d (jo

ules

)

no SB, no AB, ME (n=3) no SB, no AB, HD (n=3) no SB, no AB, survived (n=1)SB no AB, ME (n=4) SB no AB, HD (n=2) SB no AB, survived (n=4)AB no SB, ME (n=9) AB no SB, HD (n=2) AB+SB, ME (n=4)AB+SB, survived (n=2)



SUMMARY & CONCLUSIONS VIII

16. VALUE OF RESTRAINTS IN AORTIC INJURY (AI):FMVC AIs: 46 CASES

16 REACHED HOSPITAL ALIVE (35%)6 SURVIVED HOSPITAL (13%)

ALL SURVIVORS RESTRAINED, 2/3rds BY AB OR AB+SB.

LMVC AIs: 34 CASES (50% HAD SUFFICIENT ARRESTED FORWARD DELTA V COMPONENT TO CAUSE AIRBAG (AB) DEPLOYMENT)

14 REACHED HOSPITAL ALIVE (41%)7 SURVIVED HOSPITAL (21%)

6 OF THE 7 SURVIVORS HAD SB OR SB+AB.

MODEL YEAR DISTRIBUTION OF ALL COMPLETE CASES (N=876)

30 25 25

141

250

405

0

50

100

150

200

250

300

350

400

450

500

pre-1994 1994-1996 1997-2002

model year

freq

uen

cy

aortas non-aortas

** = p<0.01 vs pre-1994*** = p<0.0001 vs pre-1994

**

***

note: difference between 1994-6 and 1997-2003 was NSCIRENgraphlatrestr1.xls 11-10-2003

SUMMARY & CONCLUSIONS IX

17. EXAMINING INCIDENCE OF AI BY MODEL YEAR OF STRUCK VEHICLE: PRE 1994 (SB, BUT AB NOT REQUIRED)

AI INCIDENCE 17.5%1994-1996 (SB AND AB MANDATORY)

AI INCIDENCE 9.1% *1997-2003 (SB, AB & SIDE-STANDARDS)

AI INCIDENCE 5.8% **

18. THE DATA SUGGEST THAT THE INTRODUCTION OF SAFETY STANDARD REGULATIONS IN SUCCESSIVE MODEL YEAR VEHICLES HAVE PROGRESSIVELY REDUCED THE INCIDENCE OF AORTIC INJURIES IN DRIVERS AND FRONT-SEAT PASSENGERS OF THESE VEHICLES

*P< 0.05 VS PRE 1994** P< 0.01 VS PRE 1994

17

4

16

7

26

17

5

7

5

2

17

49

61

84

12

50

7

20

22

100

35

41

30

24

7

20

48

20

72

87

BRAIN

FACE FX.

UPEXT FX.

SPINE

THORAX

LUNG

HEART

LIVER

SPLEEN

KIDNEY

PELVIC FX.

LOWEXT FX.

BELT USE

AIRBAG DEPLOY

FATAL

Organ System

0102030405060708090100

110 0 10 20 30 40 50 60 70 80 90 100

110

Percentall frontal non-aorta cases (n=506)all frontal aorta cases (n=46)

Frontal Non-Aorta vs Aorta Injury Cases

**

**

* = p<0.05** = p<0.01

**

**

******

*

***

**

36

3

8

9

39

21

2

8

9

2

22

21

72

53

18

65

15

21

15

100

68

29

32

41

18

35

26

44

50

79

BRAIN

FACE FX.

UPEXT FX.

SPINE

THORAX

LUNG

HEART

LIVER

SPLEEN

KIDNEY

PELVIC FX.

LOWEXT FX.

BELT USE

AIRBAG DEPLOY

FATAL

Organ System

0102030405060708090100

110 0 10 20 30 40 50 60 70 80 90 100

110

Percentall lateral non-aorta cases (n=290)all lateral aorta cases (n=34)

Lateral Non-Aorta vs Aorta Injury Cases

**

**

* = p<0.05** = p<0.01

**

**

******

**

**

**

**

60

9

22

23

77

73

33

100

55

39

34

33

11

27

38

29

59

81

44

14

14

22

35

54

35

100

86

0

30

27

19

46

38

62

67

14

BRAINFACE FX.

UPEXT FX.SPINE

RIBS 1-4RIBS 5-8

RIBS 9-12THORAX

LUNGHEARTLIVER

SPLEENKIDNEY

PELVIC FX.LOWEXT FX.

BELT USEAIRBAG DEPLOY

FATAL

Organ System

0102030405060708090100

110 0 10 20 30 40 50 60 70 80 90 100

110

Percentaorta cases with rib data (n=64)thoracic non-aorta with rib data (n=37)

Aorta Injury vs Thoracic Non-Aorta Cases

*

* = p<0.05** = p<0.01

**

****

****

*

SUMMARY & CONCLUSIONS XI

19. HOWEVER, WHEN AORTIC INJURY PATIENTS WERE COMPARED TO PATIENTS WHO SUSTAINED SEVERE GRADE III OR GREATER THORACIC INJURIES WITHOUT AORTIC DISRUPTIONS, IT WAS FOUND THAT THE AORTIC INJURY PATIENTS HAD A SIGNIFICANTLY GREATER INCIDENCE OF FRACTURES OF RIBS 14 & 5-8. THEY ALSO HAD SIGNIFICANTLY MORE CARDIAC INJURIES AND PELVIC FRACTURES, BUT A MUCH LOWER INCIDENCE OF SEAT-BELT USE AND A HIGHER FATALITY RATE. IN CONTRAST, THE NON-AORTIC THORACIC INJURY PATIENTS HAD A SIGNIFICANTLY GREATER INCIDENCE OF LUNG INJURY.

SUMMARY & CONCLUSIONS XII

20. THE SIGNIFICANT INCREASE IN FRACTURES OF RIBS 1-4CONTINUED TO BE SEEN EVEN WHEN THE AORTIC INJURY SURVIVORS WERE COMPARED TO THE NON-AORTIC INJURY THORACIC TRAUMA SURVIVORS, WHO IN CONTRAST CONTINUED TO MANIFEST A SIGNIFICANTLY HIGHER INCIDENCE OF LUNG INJURY THAN THE AORTIC INURY PATIENTS. HOWEVER, THE AI SURVIVORS HAD A SIGNIFICANTLY LOWER AIRBAG DEPLOYMENT THAN THE NON-AORTIC THORACIC INJURY SURVIVORS.

CRUSH MEASUREMENTS ON SIDE IMPACT

THE ARCHIMEDES LEVER HYPOTHESIS REGARDING THE MECHANISM OF AORTIC INJURY: “GIVE ME A LEVER LONG ENOUGH, A FULCRUM AND A PLACE TO STAND, AND I WILL MOVE THE WORLD”.

A. ANATOMIC: AS THE THORACIC AORTA ARISES FROM THE HEART, IT IS SUSPENDED FROM THE GREAT VESSELS, INNOMINATE, LEFT CAROTID AND LEFT SUBCLAVIAN ARTERIES, THE LATTER BEING MOST FIXED AS IT EXITS THE THORAX OVER THE FIRST RIB. THE DESCENDING AORTA IS FIXED TO THE SPINE AND RIBS BEGINNING AT THE ORIGINS OF THE 3rd INTERCOSTAL ARTERIES. THE ISTHMUS LYING BETWEEN THE SUBCLAVIAN AND THE ORIFACES OF THE 3rd INTERCOSTALS IS UNTETHERED EXCEPT FOR A POTENTIAL TEAR-TAB AT THE LIGAMENTUM ARTERIOSUM.

B. FUNCTIONAL: THE ASCENDING AORTA AND THE ARCH AS FAR AS THE LEFT SUBCLAVIAN ARTERY, IF MADE RIGID, CANFUNCTION AS A LONG LEVER ARM WITH THE SUBCLAVIAN TAKE-OFF AS THE FULCRUM TO EXERT A LARGE TORSIONAL FORCE ON THE RELATIVELY SHORT ARM OF THE UNTETHERED ISTHMUS WHICH IS ATTACHED AT ITS LOWER END TO THE FIXED PROXIMAL DESCENDING AORTA

C. MECHANISTIC I: WITHIN 10-20 MSEC OF A CRASH MEDIATED IMPACT FORCE WHICH IS NARROWLY FOCUSED ACROSS THE REGION OF THE 2nd TO 5th RIBS (WHICH DELINEATES THE LOCUS OF THE AORTIC ARCH – ISTHMUS SYSTEM), THE INTRA-AORTIC PRESSURE RISES TO LEVELS WHICH MAY APPROXIMATE OR EXCEED 500 MM HG. THIS INTRA-AORTIC PRESSURE SELDOM RUPTURES THE AORTA IN ITSELF, BUT RATHER FUNCTIONS TO CAUSE THE ENTIRE ASCENDING AORTA – AORTIC ARCH SYSTEM TO FUNCTION AS A SINGLE TURGID, RIGID LEVER WHOSE FULCRUM IS THE SUBCLAVIAN ARTERY.

CADAVERIC INTRA-AORTIC PRESSURE: LATERAL CRASH

WSU:

D. MECHANISTIC II: AT THE SAME TIME, THE ENTIRE SYSTEM OF HEART, ASCENDING AORTA AND AORTIC ARCH MOVES TOWARD THE IMPACTING FORCE, THUS CAUSING THE AORTIC LEVER ARM TO PRODUCE A FORCEFUL TORSIONAL ROTATION OF THE ISTHMUS ON THE PROXIMAL DESCENDING AORTA, WITH ITS TEAR POINT IN THE REGION OF THE LIGAMENTUM ARTERIOSUM, WHICH IS FIXED TO THE LEFT PULMONARY ARTERY. THIS TORSIONAL FORCE, WHICH IS MAGNIFIED BY THE DIFFERENCE IN LENGTH BETWEEN THE AORTIC ARCH SYSTEM AND THE ISTHMUS, PRODUCES A SUFFICIENT AMPLIFICATION OF THE IMPACT ENERGY TRANSMITTED TO THE PATIENT’S THORAX AT THE MOMENT OF IMPACT DECELERATION VELOCITY TO TEAR THE AORTA AT THE ISTHMUS OR PROXIMAL DESCENDING AORTA.

RECOMMENDATIONS I

SLIGHTY LESS THAN HALF OF ALL FMVC SERIOUS INJURIES REQUIRING HOSPITALIZATION AND 58% OF ALL FMVC DEATHS AND 65% OF THE FMVC AORTIC INJURIES OCCURRED IN CRASHES WHERE THE DELTA V WAS GREATER THAN THE 48 KPH AT WHICH THE FEDERAL CRASH SAFETY STANDARD TESTS ARE CONDUCTED, AND THE IMPACT ENERGY EXCEEDED 155,524 JOULES.

IN LMVCs 64% OF THE DEATHS AND 64% OF THE AORTIC INJURIES OCCURRED IN CRASHES WHERE THE DELTA V WAS GREATER THAN 36 KPH, AND THE IMPACT ENERGY EXCEEDED 92,956 JOULES.

RECOMMENDATIONS II

TO REDUCE SERIOUS INJURES AND RELATED FMVC DEATHS, CRASH SAFETY TESTING SHOULD BE CARRIED OUT AT A DELTA V EQUAL TO THE MEAN PLUS ONE STANDARD DEVIATION OF THE ACTUAL DELTA V FOUND IN THE CIREN MULTICENTER STUDY. THIS LEVEL OF DELTA V WOULD BE 48±19.7 KPH = 67.7 KPH (OR 42 MPH) WITH A CORRESPONDING IMPACT ENERGY OF 286,775 JOULES.

IN LMVCs THIS DELTA V WOULD BE 36±16.4 KPH = 52.4 KPH (OR 33 MPH), WITH A CORRESPONDING IMPACT ENERGY OF 179,299 JOULES, AS ACTUALLY MEASURED AT IMPACT.

THESE LEVELS OF CRASH DYNAMICS SHOULD ENCOMPASS 84%OF ALL SERIOUS MVC INJURIES ADMITTED TO LEVEL I TRAUMA CENTERS.

RECOMMENDATIONS III

IT WOULD APPEAR THAT IN FMVCs THE COMBINATION OF SEAT-BELT RESTRAINT USAGE PLUS AIRBAG DEPLOYMENT HAS THE BEST PROTECTIVE EFFECT IN THE REDUCTION OF MORTALITY AND SEVERE BRAIN AND THORACIC INJURIES, EVEN AT HIGH DELTA Vs AND LARGE VEHICLE IMPACT ENERGY (IE) DISSIPATIONS. THIS SUGGESTS THAT THE OCCUPANT NEEDS TO BE HELD IN A POSITION WHICH ENSURES THAT THE AIRBAG CAN MOST EFFECTIVELY BUFFER THE CRASH IMPACT ENERGY DISSIPATED INTO THE VEHICLE.

RECOMMENDATIONS IV

IT ALSO IMPLIES THAT IN LATERAL MOTOR VEHICLE CRASHES A SIMILAR COMBINATION OF EFFECTIVE SEAT-BELTIMMOBILIZATION TOGETHER WITH SIDE-AIRBAGDEPLOYMENTS FOCUSED AT BUFFERING THE HIGH IE TRANSMITTED TO THE HEAD, UPPER THORAX (INCLUDING RIBS 1-4), AND PELVIS WILL PRODUCE A PROTECTIVE EFFECT ON OVERALL MVC MORTALITY AND MORE SPECIFICALLY, ON AORTIC INJURY PRODUCTION.

DECELERATION VELOCITY AND ENERGY … · car vs car (n=147) car vs SUVT (n=75) car vs nonvehicle...

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