ABDOMINAL INJURIES BEFORE AND AFTER SEAT BELT LEGISLATION
RYAN AND RAGAZZON
ABDOMINAL INJURIES IN SURVlVORS OF ROAD TRAUMA BEFORE AND SINCE SEAT BELT LEGISLATION IN VICTORIA RYAN' AND RALPH RAGAZZON? St Vincent's Hospital, Melbourne PETER
At St Vincent's Hospital, Melbourne, the number of patients admitted annually with road crash injuries has remained almost constant for the past 14 years. Comparing admissions in the seven years before and during the seven years since enactment of seat belt legislation in Victoria, there has been no change in the proportion Of those admitted with abdominal injuries, in the number of associated non-abdominal severe injuries, or in the death rate of those admitted with abdominal injuries. There has, however. been a significant increase in the number of patients admitted with injuries of the gastrointestinal tract and diaphragm. It is suggested that this increase is due to incorrect wearing of the lap component of seat belts with resulting acute abdominal compression.
COMPULSORY wearing of seat belts in Australia has reduced the vehicle occupant death rate (Henderson and Wood, 1973). Since the magnitude of the road crash impacts remains unchanged, some previously lethal forces must have been distributed through the seat belt mechanism. That such forces may themselves cause injury has been pointed out by Mackay et alii (1975). Vellar etalii (1976), in o u r hospital, have drawn attention to the emergence of bowel rupture as a "seat belt syndrome". Before the introduction of seat belt legislation one of the authors (P.R.) had correlated pelvic skeletal injury patterns with pelvic visceral injury (Ryan, 1971) and was interested i n studying further the effect of blunt trauma on abdominopelvic viscera. In order to study the pattern and mechanism of seat belt injury to the abdominal contents, we decided to carry out a retrospective study of patients admitted to St Vincent's Hospital with abdominal injuries following road crashes before and since the enactment of compulsory seat belt wearing legislation in Victoria in July 1970. PATIENTS AND METHOD The periods studied were 1964 to 1970and 1971 to 1977, seven years before and seven years after introduction of seat belt legislation The recordsof all car occupants admitted to St Vincent s Hospital, Melbourne, with abdominal injuries during this 14year period were examined Abdominal injuries included not merely damage to abdominal viscera Surgeon to Inpatients Surglcal Registrar Reprints Mr Peter Ryan 20 Collins Street Melbourne Victoria 3000
200
(liver, spleen, pancreas, gastrointestinal tract, mesentery, omentum), but also injuries to kidney, ureter and bladder, retroperitoneat haematoma, and ruptured diaphragm. Associated severe injuries were recorded, "severe" being defined for this purpose as from 2 (moderate) to 5 (serious - survival improbable) on the Abbreviated Injury Scale (A.I.S.) as described by States (1969). Obviously this study gives no idea of the effect of seat belts on the overall death rate of car occupants, since only those surviving the crash reached hospital. Information from our hospital records about whether victims were wearing belts at the time of the crash is inadequate, but the seat belt wearing rate for Victoria since the introduction of legislation in 1970 has been found by the Road Safety and Traffic Authority to be about 90% and it is the same for New South Wales (Holt and Vazey, 1977). No information was available stating whether belts were correctly worn by victims of crashes. Case populations in the periods 1964 to 1970 and 1971 to 1977 were comparable regarding number (81 in the first period, 70 in the second), sex (23 females and 58 males in the first period, 26 females and 44 males in the second), and age (mean age in the first period 30.7, 30.4 years in the second). RESULTS The proportion of patients admitted with abdominal injuries compared with total road 'trauma admissions at St Vincent's Hospital was thesame for both periods, being 81/3,048 (2.7%) from 1964 to 1970 and 70/3,302 (2.1%) for the period 1971 to 1977. There were 101 abdominal visceral injuries in AUST N.Z. J. SURG. VOL 49-No
2, APRIL1979
ABDOMINAL INJURIES BEFORE AND AFTER SEAT BELT LEGISLATION TABLE 1 Abdominal Visceral inluries including Refroperitoneal Haernafoma Ruptured Diaphragm and Pelvic Visceral lniuries 1964 1977 (Deaths in Parentheses)
-~_ _ _ _ ~
__
-__
.~
1964-1970 1971 1977 Liver Spleen Kidney Pancreas Stomach Duodenum Jelunum Mesentery Omentum Colon Bladder Retroperitoneal haematoma Non-specified Ruptured diaphragm
2 1 3 1 1 5 (3) 12 (5) 2 (2)
1
7 3 (1) 0 2 3 (1) 13 1 (1)
9 (3) 94
101
the earlier and 94 in the later period (Table 1). Thus the number of abdominal viscera injured per victim was 1.25 for the pre-seat-belt legislation period and 1.34 since seat belt legislation, an insignificant difference. The apparent diminution in death rate during the later period ( 8 / 7 0 , = 11.0%, compared with 13/81, = 16.0%) is not statistically significant, nor is the apparent difference between the mean number of severe (A.I.S. 2 to 5) non-abdominal injuries per victim (55/81, = 0.68, in 1964 to 1970, compared with 67/70, = 0.96, from 1971 to 1977). When we come to compare injury rates of some abdominal viscera among the patients admitted in the eras before and after seat belt legislation (Table Z ) , several differences emerge. Though the injury
RYAN AND RAGAZZON
m i n e s in frontal imoacts (Holt and Stott. 1976). If the "lap strap angle'" (Holt and Stott) is too steep, that is, if the ends of the lap component are anchored too far back behind the pelvis, or if the lap cornponent is loosely fastened (Holt and Vazey, 1977), "submarining" is likely to occur (Vazey and Holt. 1976), with direct injury to intraabdominal organs by the lap component which had ridden up on tothe abdomen. While direct injury by the lap component will explain the increased incidence of gastrointestinal tract injuries in our patients admitted since the introduction of seat belt legislation, it will not explain the increased incidence of diaphragm injury. We suggest that where lap belts ride up on to the abdomen, not merely is direct or shearing injury of viscera likely, but also sudden sharp increase in thrusting the intraabdominal pressure (Figure l), liver against the diaphragm and injuring it, or rupturing the diaphragm itself. It is interesting to note
TABLE2 Comparison of Injury Rafes o f some Abdominal Viscera ~
1964-1970 181 pts) 1971-1 977 (70 pts)
Liver
Spleen
Kidney
ti I T
Diaphragm
2112621
22(27%1
28135%)
8(tO%)
l(l%)
21[30%)
23(33%)
13(19%)
8(11%)
9[139%)
'The only significant differences (P less than 0 05) are increases in ti I T inluries and ruptured diaphragm since seal bell legislation and decrease 11 liver inluries
rates of spleen and kidney remain the same in both periods, there is a significant increase ( P less than 0 05) in the proportion of abdominal trauma patients suffering injuries of the gastrointestinal tract and diaphragm and a significant decrease in the proportion with liver injuries. DIscuSSION For maximum safety, the lap component of the standard lap-sash belt should be fastened firmly over the upper thighs, making an angle of about 90" with the floor of the vehicle and situated in such a way as to be locked below the anterior superior iliac AUST N Z J SURGVOL 49-NO 2, APRIL 1979
x FlGURE 1 (upper) a correctly placed lap component exerting pressure against the upper thighs (lower) an upward riding lap component compressing the abdomen and rupturing the diaphragm
20 1
ABDOMINAL INJURIES BEFORE AND AFTER SEAT BELT LEGISLATION
that our patients suffered one injury or the other the eight patients with ruptured liver had no rupture of the diaphragm, and the nine patients with ruptured diaphragm had no liver injury. This indicated that where the diaphragm ruptures because of raised intraabdominal pressure the liver is spared: where the diaphragm remains intact, the liver is broken against it. The higher incidence of liver injuries in the pre-seat-belt era may have been due to crushed chest, now prevented by the seat belt sash. We believe the value of this study is that, while demonstrating that there is a real pattern of abdominal seat belt trauma (with injuries of diaphragm and gastrointestinal tract), these injuries are due to incorrect application of the lap component of the seat belt and should be prevented by firm application of this lap component vertically over the upper thighs. Holt and Stott also point out that compulsory introduction in 1975 of automatically adjusting front seat belts (with emergency locking retractors) should reduce the incidence of “some injuries” particularly, we believe, those that we have described as due to riding up of the lap belt on to the vulnerable abdomen.
CONCLUSIONS 1. Since the introduction of seat belt legislation in Victoria in 1970, the pattern of abdominal injuries among car occupants admitted to St Vincent’s
202
RYAN AND RAGAZZON
Hospital has changed. Since compulsory seat belt wearing, the proportion of those with injuries to the diaphragm and gastrointestinal tract has significantly increased. 2. We suggest that while direct injury by the lap bglt riding up on to the abdomen may explain increased damage to the gastrointestinal tract, the reason for the increased incidence of diaphragm damage is a sharp rise in intraabdorninal pressure caused by impact of the lap component of the seat belt on the abdomen. REFERENCES HENDERSON, J. M. and WOOD, R (1973). New South Wales Department of Motor Transport Traffic Accident Research Unit, Report No. 4/73 HOLT. B. W. and STOTT.J . D. (1976). NewSouth Wales Department of Motor Transport Traffic Accident Research Unit, Report No 7/76, HOLT,B. W. and VAZEY, B. A., (1977). New South Wales Department of Motor Transport Traffic Accident Research Unit, Report No. 1/77. MACKAY,G M., GLOYNS,P. F., HAYES, H. R. M., GRIFFTHS, D. K. and RATTENBURY, S. J. (1975). Proceedings of Second International Conference on Biomechanics of Serious Trauma, I R C.0.B I . , Birmingham. RYAN, P. (1971), Med. J. AuSt., 1: 475. STATES, J. D. (1969). Proceedings 13th Stapp. Car Crash Conference, S.A.E., Paper No. 690810, Soclety of Automotive Engineers, Boston. VAZEY. B A. and HOLT, 8. W. (1976), New South Wales Department of Motor Transport Traffic Accident Research Unit, Report No 2/76. VELLAR. I. D ,VELLAR, D. J and MULLANY, C. J.. (1976), Med. J. Aust, 1: 694.
AUST N.Z. J . SURG,VOL @-No
2, APRIL, 1979
RYAN AND RAGAZZON
ABDOMINAL INJURIES IN SURVlVORS OF ROAD TRAUMA BEFORE AND SINCE SEAT BELT LEGISLATION IN VICTORIA RYAN' AND RALPH RAGAZZON? St Vincent's Hospital, Melbourne PETER
At St Vincent's Hospital, Melbourne, the number of patients admitted annually with road crash injuries has remained almost constant for the past 14 years. Comparing admissions in the seven years before and during the seven years since enactment of seat belt legislation in Victoria, there has been no change in the proportion Of those admitted with abdominal injuries, in the number of associated non-abdominal severe injuries, or in the death rate of those admitted with abdominal injuries. There has, however. been a significant increase in the number of patients admitted with injuries of the gastrointestinal tract and diaphragm. It is suggested that this increase is due to incorrect wearing of the lap component of seat belts with resulting acute abdominal compression.
COMPULSORY wearing of seat belts in Australia has reduced the vehicle occupant death rate (Henderson and Wood, 1973). Since the magnitude of the road crash impacts remains unchanged, some previously lethal forces must have been distributed through the seat belt mechanism. That such forces may themselves cause injury has been pointed out by Mackay et alii (1975). Vellar etalii (1976), in o u r hospital, have drawn attention to the emergence of bowel rupture as a "seat belt syndrome". Before the introduction of seat belt legislation one of the authors (P.R.) had correlated pelvic skeletal injury patterns with pelvic visceral injury (Ryan, 1971) and was interested i n studying further the effect of blunt trauma on abdominopelvic viscera. In order to study the pattern and mechanism of seat belt injury to the abdominal contents, we decided to carry out a retrospective study of patients admitted to St Vincent's Hospital with abdominal injuries following road crashes before and since the enactment of compulsory seat belt wearing legislation in Victoria in July 1970. PATIENTS AND METHOD The periods studied were 1964 to 1970and 1971 to 1977, seven years before and seven years after introduction of seat belt legislation The recordsof all car occupants admitted to St Vincent s Hospital, Melbourne, with abdominal injuries during this 14year period were examined Abdominal injuries included not merely damage to abdominal viscera Surgeon to Inpatients Surglcal Registrar Reprints Mr Peter Ryan 20 Collins Street Melbourne Victoria 3000
200
(liver, spleen, pancreas, gastrointestinal tract, mesentery, omentum), but also injuries to kidney, ureter and bladder, retroperitoneat haematoma, and ruptured diaphragm. Associated severe injuries were recorded, "severe" being defined for this purpose as from 2 (moderate) to 5 (serious - survival improbable) on the Abbreviated Injury Scale (A.I.S.) as described by States (1969). Obviously this study gives no idea of the effect of seat belts on the overall death rate of car occupants, since only those surviving the crash reached hospital. Information from our hospital records about whether victims were wearing belts at the time of the crash is inadequate, but the seat belt wearing rate for Victoria since the introduction of legislation in 1970 has been found by the Road Safety and Traffic Authority to be about 90% and it is the same for New South Wales (Holt and Vazey, 1977). No information was available stating whether belts were correctly worn by victims of crashes. Case populations in the periods 1964 to 1970 and 1971 to 1977 were comparable regarding number (81 in the first period, 70 in the second), sex (23 females and 58 males in the first period, 26 females and 44 males in the second), and age (mean age in the first period 30.7, 30.4 years in the second). RESULTS The proportion of patients admitted with abdominal injuries compared with total road 'trauma admissions at St Vincent's Hospital was thesame for both periods, being 81/3,048 (2.7%) from 1964 to 1970 and 70/3,302 (2.1%) for the period 1971 to 1977. There were 101 abdominal visceral injuries in AUST N.Z. J. SURG. VOL 49-No
2, APRIL1979
ABDOMINAL INJURIES BEFORE AND AFTER SEAT BELT LEGISLATION TABLE 1 Abdominal Visceral inluries including Refroperitoneal Haernafoma Ruptured Diaphragm and Pelvic Visceral lniuries 1964 1977 (Deaths in Parentheses)
-~_ _ _ _ ~
__
-__
.~
1964-1970 1971 1977 Liver Spleen Kidney Pancreas Stomach Duodenum Jelunum Mesentery Omentum Colon Bladder Retroperitoneal haematoma Non-specified Ruptured diaphragm
2 1 3 1 1 5 (3) 12 (5) 2 (2)
1
7 3 (1) 0 2 3 (1) 13 1 (1)
9 (3) 94
101
the earlier and 94 in the later period (Table 1). Thus the number of abdominal viscera injured per victim was 1.25 for the pre-seat-belt legislation period and 1.34 since seat belt legislation, an insignificant difference. The apparent diminution in death rate during the later period ( 8 / 7 0 , = 11.0%, compared with 13/81, = 16.0%) is not statistically significant, nor is the apparent difference between the mean number of severe (A.I.S. 2 to 5) non-abdominal injuries per victim (55/81, = 0.68, in 1964 to 1970, compared with 67/70, = 0.96, from 1971 to 1977). When we come to compare injury rates of some abdominal viscera among the patients admitted in the eras before and after seat belt legislation (Table Z ) , several differences emerge. Though the injury
RYAN AND RAGAZZON
m i n e s in frontal imoacts (Holt and Stott. 1976). If the "lap strap angle'" (Holt and Stott) is too steep, that is, if the ends of the lap component are anchored too far back behind the pelvis, or if the lap cornponent is loosely fastened (Holt and Vazey, 1977), "submarining" is likely to occur (Vazey and Holt. 1976), with direct injury to intraabdominal organs by the lap component which had ridden up on tothe abdomen. While direct injury by the lap component will explain the increased incidence of gastrointestinal tract injuries in our patients admitted since the introduction of seat belt legislation, it will not explain the increased incidence of diaphragm injury. We suggest that where lap belts ride up on to the abdomen, not merely is direct or shearing injury of viscera likely, but also sudden sharp increase in thrusting the intraabdominal pressure (Figure l), liver against the diaphragm and injuring it, or rupturing the diaphragm itself. It is interesting to note
TABLE2 Comparison of Injury Rafes o f some Abdominal Viscera ~
1964-1970 181 pts) 1971-1 977 (70 pts)
Liver
Spleen
Kidney
ti I T
Diaphragm
2112621
22(27%1
28135%)
8(tO%)
l(l%)
21[30%)
23(33%)
13(19%)
8(11%)
9[139%)
'The only significant differences (P less than 0 05) are increases in ti I T inluries and ruptured diaphragm since seal bell legislation and decrease 11 liver inluries
rates of spleen and kidney remain the same in both periods, there is a significant increase ( P less than 0 05) in the proportion of abdominal trauma patients suffering injuries of the gastrointestinal tract and diaphragm and a significant decrease in the proportion with liver injuries. DIscuSSION For maximum safety, the lap component of the standard lap-sash belt should be fastened firmly over the upper thighs, making an angle of about 90" with the floor of the vehicle and situated in such a way as to be locked below the anterior superior iliac AUST N Z J SURGVOL 49-NO 2, APRIL 1979
x FlGURE 1 (upper) a correctly placed lap component exerting pressure against the upper thighs (lower) an upward riding lap component compressing the abdomen and rupturing the diaphragm
20 1
ABDOMINAL INJURIES BEFORE AND AFTER SEAT BELT LEGISLATION
that our patients suffered one injury or the other the eight patients with ruptured liver had no rupture of the diaphragm, and the nine patients with ruptured diaphragm had no liver injury. This indicated that where the diaphragm ruptures because of raised intraabdominal pressure the liver is spared: where the diaphragm remains intact, the liver is broken against it. The higher incidence of liver injuries in the pre-seat-belt era may have been due to crushed chest, now prevented by the seat belt sash. We believe the value of this study is that, while demonstrating that there is a real pattern of abdominal seat belt trauma (with injuries of diaphragm and gastrointestinal tract), these injuries are due to incorrect application of the lap component of the seat belt and should be prevented by firm application of this lap component vertically over the upper thighs. Holt and Stott also point out that compulsory introduction in 1975 of automatically adjusting front seat belts (with emergency locking retractors) should reduce the incidence of “some injuries” particularly, we believe, those that we have described as due to riding up of the lap belt on to the vulnerable abdomen.
CONCLUSIONS 1. Since the introduction of seat belt legislation in Victoria in 1970, the pattern of abdominal injuries among car occupants admitted to St Vincent’s
202
RYAN AND RAGAZZON
Hospital has changed. Since compulsory seat belt wearing, the proportion of those with injuries to the diaphragm and gastrointestinal tract has significantly increased. 2. We suggest that while direct injury by the lap bglt riding up on to the abdomen may explain increased damage to the gastrointestinal tract, the reason for the increased incidence of diaphragm damage is a sharp rise in intraabdorninal pressure caused by impact of the lap component of the seat belt on the abdomen. REFERENCES HENDERSON, J. M. and WOOD, R (1973). New South Wales Department of Motor Transport Traffic Accident Research Unit, Report No. 4/73 HOLT. B. W. and STOTT.J . D. (1976). NewSouth Wales Department of Motor Transport Traffic Accident Research Unit, Report No 7/76, HOLT,B. W. and VAZEY, B. A., (1977). New South Wales Department of Motor Transport Traffic Accident Research Unit, Report No. 1/77. MACKAY,G M., GLOYNS,P. F., HAYES, H. R. M., GRIFFTHS, D. K. and RATTENBURY, S. J. (1975). Proceedings of Second International Conference on Biomechanics of Serious Trauma, I R C.0.B I . , Birmingham. RYAN, P. (1971), Med. J. AuSt., 1: 475. STATES, J. D. (1969). Proceedings 13th Stapp. Car Crash Conference, S.A.E., Paper No. 690810, Soclety of Automotive Engineers, Boston. VAZEY. B A. and HOLT, 8. W. (1976), New South Wales Department of Motor Transport Traffic Accident Research Unit, Report No 2/76. VELLAR. I. D ,VELLAR, D. J and MULLANY, C. J.. (1976), Med. J. Aust, 1: 694.
AUST N.Z. J . SURG,VOL @-No
2, APRIL, 1979
