INJURY PATTERNS I N CAR ACCIDENTS

NELSON

ASPECTS OF INJURY PATTERNS IN AUTOMOBILE ACCIDENTS PETER G. NELSON Royal Melbourne Hospital During t h e period June 1971 to June 1973, the injuries o f 34,378 persons involved i n accidents attended by ambulance officers, and treated b y hospitals, together w i t h the injuries received by 1,699 victims investigated by coroners, w e r e analysed. Clear-cut injury patterns emerged for different types of road users. Pedestrians in general suffered injuries ‘of greater severity than cyclists, who in t u r n had injuries of greater severity than vehicle occupants. T h e extent to which car occupant injury patterns are moAified by seat belts is demonstrated. Injuries suffered b y the wearers o f seat belts occur less frequently, and are less severe, less likely t o prove fatal, and less likely to cause long stays i n hospitals.

I NJURIES sustained in automobile accidents in the State of Victoria during the period June 1971 to June 1973 have been studied and presented in detail elsewhere (Nelson, 1974). This paper briefly summarizes certain aspects of this study, namely the pattern of injuries among difierent categories of road users, and the way in which injuries and injury patterns in car occupants are modified by seat belts.

MATERIAL A N D METHODS The data were provided in a standard format amenable to computer processing by ambulance officers throughout the State, by doctors in major metropolitan and country hospitals, and by coroners after performance of postmortem examinations in fatal cases. In the period in question, reports on 19,589 persons involved in accidents attended by ambulance officers, 34,378 persons treated by hospitals, and 1,699 persons whose deaths were investigated by coroners, were analysed. This represents 40% of all accidents attended by ambulance officers, 80% of all injured victims, and 90% of all fatalities for the period in Victoria. Matching of accident circumstances and injuries received, together with analysis of the data, was carried out by using computer facilities. Various techniques were used to compare injury severity (Nelson, 1974)~ and these

included a modified abbreviated injury scale (AIS) of the American Medical Association, and a modified injury severity score (ISS, Baker et alii, 1974), as well as other special means of comparison which evolved with the study.l

RESULTS Individual patterns in road users.-Detailed injury information was collected by using an anatomical basis within a broad regional classification into head and neck, chest, abdomen and pelvis, and upper and lower extremity regions. Individual injuries were too numerous to tabulate in this paper, and some selections only from the detailed tabulations are described (Table I ) . Ruptured spleen and liver occur no more commonly in any one group of victims. Whiplash injury to the neck, as might be expected, is more common in car occupants. Fractures

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The abbreviated injury scale (AIS) is a measure developed by the American Medical Association whereby a “grade” is allotted to a given injury according to its threat to life. For example, a fractured digit is placed in AIS Grade I, while a lacerated aorta is classified as AIS Grade 5. The survey data have been adapted to conform to a format based on this scale. The injury severity score (ISS) of Baker is a measure of the threat to life computed by summing the squares of the highest AIS grade injury in each of the most severely injured body areas. The modified ISS used in this survey is computed by summing the squares of the I A S grades of all injuries to all body areas.

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INJURY PATTERNS IN CAR ACCIDENTS

body region amongst vehicle occupants, pedestrians, cyclists, and the total group. A fatal outcome resulting from injuries received occurs more frequently among pedestrians than in either car occupants or cyclists, in whom death occurs from injury with equal frequency. O n the other hand, while major non-fatal injuries form a higher proportion of injuries received in the pedestrian group than others, injuries to cyclists of this degree form a higher proportion of injuries received than they do to car occupants. In all groups, head, chest, and abdominal injuries contribute most significantly to a fatal outcome. There are of course often multiple injuries in dead victims, and it is evident that the probability of dying (one of the measures used to compare injury severity) is directly related to the number of regions of the body involved in major injuries (Table 3 ) Skeletal injuries, such as those to the spine, pelvis and extremities, do not contribute greatly to a fatal outcome. However, major injuries, particularly to the lower extremities,

of the leg and thigh occur much more commonly in pedestrians and cyclists and most commonly in pedestrians. Fractured pelvis similarly occurs much more commonly in pedestrians. Major aortic rupture occurs with TABLEI Selected Individual Injuries in Road Users Sumben of different types of injury, as a percentage of iiumber of persons injured

______ Occupaiits Pedestrian.

Injury

,"

-

Rupturedspleen . . Ruptured liver . Whiplash injury to neik Fractured thigh . . Fractured pel& . . Major aortic rupture . , Fractured leg . . . .

.

. .

1'1

:

4'0

1.9 1-6 0.5 1'4

. .

0

ro

70

1'4 1'3

0.9

0.5 8.8 6.9

5.1

' "

0'4 8.6

1'4

. . . . ..

-

Cyclists

1'0

0.5 1.9

11.7

equal frequency in all groups and does not appear, as has been thought, to be an injury peculiar to the deceleration caused by impacts of the chests of drivers with steering wheels. Regional injury patterns in road users.Table 2 shows the degree of injury to each

TABLE 2 Region& Injury Patterns in Road Users

Percentage of total with Number of casualties

Status of casualty

Region of body injured

No injury Vehicle occupant

. . . . . . . . . . . .

23,278

'

Pedestrian

. . . . . . . . . . . . . .

3.117

. . . . . . . . . . . . . .

..

~~

Total (including 6,576 persons of unknown status)

3,106

36,077

I ~~~~~

~

?LUST. N.Z. J. SURG., VOL. 47-No.

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%

Major but not fatal injury

%

Fatal injury

x2.9

Head and neck Chest Abdomen and neck Spine and pelvic bones Upper extremities Lower extremities

41.4 78.8 91.0 97.0

52.6 17.5 6.6 1'5

"3 1'3

75.8

22.0

2.7.

1'1 0'2 0'0

68.2

28.0

3'6

0'2

Any

13.5

73.6

8.5

4.4

Head and neck Chest Abdomen and neck Spine and pelvic bones Upper extremities Lower extremities

41'5 84.0 86.6 92 '0 67.3 44'3

43'2 10.7 9'0

5'6

9'7 2.8 1'7

Any Cyclist

%

Minor injury only

Head and neck Chest Abdomen and neck Spine and pelvic bones Upper extremities Lower extremities

Head and neck Chest Abdomen and neck Spine and pelvic bones Upper extremities Lower extremities

2'4

28.6 39.8

6.6 __ _----60.5 -

1-8

2.5

1.9

2'7 4.8 4.0 15'0

0.9

20.9

12.0

3'3 1'4 0.9 0.3

0.8 0.1

61.0 86.4 87.5 96.5 57.1 36.3

1.8

3'7 1.3 1.4 1.4

374 48.8

5.1

0'0

14.6

0.3

43'5

49'5

3'7 1.9 1'4 1'7

3'3 1.8

80.5

32.0

3'1

10.9 10'2

15.8

7'2 90'3 96.5 73'4 63.2

1.6 23'9 30.8

1'1 0'2

2'7

0'0

5.8

0.2

lNJURY PATTERNS I N CAR ACCIDENTS

are very common, particularly in pedestrians and cyclists, and place a great load on casualty and hospital services. The severity of injury in road users.-To compare injuries in different groups, the development of a means to express injury severity in a simple way presents problems (Nelson, 1974). The average injury severity TABLE3 The Role of Multzplp Injuraes Number of regions reported as Number of Number of Probability of dying having major injuries persons persons injured killed 30,223 3,444 572

0

I 2

105

I

625 511 283 127 40 8

34.378

1,699

3 4 5 6

112

22

4

Total

*a03 '154 '472 +716 '909 .889

Total

..

Number of Average ISS casualties 23.278 3.117 3,106 6,576

36,077

TABLE5 Victoriais Accident Statistics

'047

TABLE4 The Severity of Injuries to Road Users

Occupant Pedestrian Cvclist Not known'

the number of intersection accidents ; the numerous Australian Design Rules which have required vehicle manufacturers to meet increasingly higher standards have the same effect ; greater police activity and newspaper and media emphasis on the causes and hazards of road accidents also play a part. Comparison of injuries of occupants with and without seat belts does not of itself provide proof of the value of seat belts unless identical crashes are studied. The difficulty with the study on which the data are based is that no measure of crash severity was possible. It will be obvious in a study where entry to the series is conditional upon at least one occupant receiving an injury, that if seat belts do confer

,852

score (ISS) is such a measure. Table 4 compares the severity of injuries among road user groups. Pedestrians sustained injuries of greater severity than cyclists, who in turn had injuries of greater severity than vehicle occupants. Numerically, of course, car occupants exceed both pedestrians and cyclists in respect of the volume of injuries requiring treatment.

Status of casualtv

NELSON

7'5 13'3 9.6 7'0

8-1

THE MODIFICATION OF CAR OCCUPANT INJURY PATTERNS BY SEAT BELTS On December 22, 1970, Victorian legislation made it compulsory for vehicle occupants aged eight years and over to wear seat belts, if in positions fitted with belts. From that time (Table 5 ) the number of persons killed and injured in road traffic accidents in Victoria per 10,000 vehicles registered has dropped dramatically. While it is tempting to ascribe this entirelv to the legislation, other factors have probably contributed ; for example, the increasing use of traffic signs and lights reduces

Persons killed or injurrd in road traffic accidents per 10,000registered vehicles

Year Killed 1968 1964 1970

1971 1972 1973

Killed o r injured

8.0

194.6

8.1 8.1 6.7 6.4 6.2

I W ' O

188.7 161.8 149'6 138.9

safety, then a more serious accident will be necessary to bring about entry of the injured occupant to the series. This of course makes such comparisons very difficult. However, there are observed differences between belted and unbelted occupants in 6,526 victims in respect of whom this information was known (Table 6). If one interprets these results with the caution referred to above, there would seem to be a trend in the following direction. Persons wearing seat belts received fewer injuries of any type to the head and neck region. They also received fewer major or fatal injuries to the chest, abdomen and pelvis, spine and pelvic bones, and upper extremities, but more minor injuries. The proportions of fatal and major and minor injuries to the lower extremities were similar for those injured, whether or not they were wearing seat belts The nature of injuries received by vehicle occupants wearing seat belts is thus markedly different from that involving occupants without belts. I n general, the injuries received by those with belts are less likely to prove fatal, and less likely to cause long stays in hospital. AUST. N.Z. J. SURG., VOL. 47-No.

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INJURY PATTERNS I N CAR ACCIDENTS TABLE 6 Injuries amongst Belt Weavers and Non- Wearers

Percentage 01 total witk Number of casualties

Status of casualty

Region of body injured No injury

Vehicle occupant with seat belt

..

..

..

..

Vehicle occupant without seat belt

..

..

2,276

..

4,250

hljnor injury only

%

%

42.3 73'3

22'4

88.4

8.6

96.6 73.2 66.2

1'7

24.2

Any Head and neck Chest Abdomen and pelvis Spine and pelvic bones Upper extremities Lower extremities

9'7

Head and neck Chest Abdomen and pelvis Spine and pelvic bones Upper extremities Lower extremities

52.2

Major but not fatal injury

Fatal injury

%

%

3'3 2.3

2.2

2.0

1'5

0.1

28.5

1.6 2.6 5'1

12.0

72'7

11.2

4'1

31-1 75.7 89.7 96.2 74'0 65.1

58.7 18.7 6.6

5'4 2.8 2'0 2'1

4.8 2.8 1'7 0'3

22'1 29.0

3'9

0'0

69.4

14'0

6.9

1.4

0.0 0'2

. . . . . . . . . . . . . . . . . . 5.8 . . . . 0'1. Any

For a variety of different measures used to indicate injury severity, seat belts appear to reduce the average severity of injuries received in accidents (Table 7). TABLE7 Average injury seventy

Injury severity measure

With seat belt Without seat belt Square root of injury seventy score

2.02

Probability of any severe injury, if _ . . _ .. .. injured

.z80

Number of body regions with major injuries per injured person . . .

'21

.

Number of days in hospital per nonfatally injured person .. .. Probability of death, if injured

..

2'39 .329

'31

2.6

fractured facial bones, fractures of the chest wall, injured lung, injured aorta, injured spleen, injured liver, and fractured thigh. With the exception of ruptured spleen and fractured thigh, all these injuries were significantly more likely to occur in unbelted occupant casualties. Fractured skull, fractured skull with intracranial compression, and aortic rupture were also significantly more common amongst unbelted occupant fatalities. Other differences between injuries sustained by those wearing and those not wearing belts were suggested by the data, but were not found to be statistically significant.

3'3

-041

-069

In terms of individual injuries, Cameron and Nelson (1976), using the survey data, identified the more commonly occurring severe injuries amongst car occupant casualties and car occupant fatalities. These were: fractured skull, fractured skull with intracranial compression, severe primary brain damage,

REFERENCES

BAKER,S. P., O'NEILL, B. and HADDON,w., JR, (1974), J . Trauma, 14: 187. CAMERON, M. H. and NELSON,P. G. (1976), Proceedings of the VIth International Conference of the International Asociation for Accident and Traffic Medicine, Melbourne, January 31February 4, 1977, awaiting publication. NELSON,P. G. (1974), "Pattern of Injury Survey of Automobile Accidents, Victoria, Australia. June rg71-June 1973", A. H. Massina : Melbourne.

It is becoming increasingly easy to treat disease, but increasingly difficult to treat patients. -W. D. Wylie, 1975, Ann. roy. ColE. Surg. EEgE., 56: 1810. AUST. N.Z. J. SURG.,VOL. 47-NO.

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Aspects of injury patterns in automobile accidents.

INJURY PATTERNS I N CAR ACCIDENTS NELSON ASPECTS OF INJURY PATTERNS IN AUTOMOBILE ACCIDENTS PETER G. NELSON Royal Melbourne Hospital During t h e pe...
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