deceleration velocity and energy … · car vs car (n=147) car vs suvt (n=75) car vs nonvehicle...
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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
100000
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500000
600000
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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
)
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
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
)
lived (n=246) died (n=78)
C:/crash/CIRENSQL/CIRENgraphlatrestr1.xls 11-08-03
= median (33 kph)= mean (36.0 ±16.2 kph)
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
= median (46 kph)= mean (48.0 ±19.7 kph)
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
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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
C:/crash/CIRENSQL/CIRENgraphlatrestr1.xls 11-08-03
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
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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
= median (46 kph)= mean (48.0 ±19.7 kph)
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)
C:/crash/CIRENSQL/CIRENgraphlatrestr1.xls 11-10-03
= median (33 kph)= mean (36.0 ±16.2 kph)
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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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)
= median (46 kph)= mean (48.0 ±19.7 kph)
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
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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)
= median (33 kph)= mean (36.0 ±16.2 kph)
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
200000
300000
400000
500000
600000
700000
800000
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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=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
= median (46 kph)= mean (48.0 ±19.7 kph)
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)
C:/crash/CIRENSQL/CIRENgraphlatrestr1.xls 11-08-03
= median (33 kph)= mean (36.0 ±16.2 kph)
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.