Severity of Placental Abruption in Restrained Pregnant Vehicle Drivers: Correct Seat Belt Use Confirmed by Finite Element Model Analysis.

Despite wearing a seat belt, pregnant drivers often suffer from negative fetal outcomes in the event of motor accidents. In order to maintain the safety of pregnant drivers and their fetuses, we assessed the severity of placental abruption caused by motor vehicle collisions using computer simulations. We employed a validated pregnant finite element model to determine the area of placental abruption. We investigated frontal vehicle collisions with a speed of 40 km/h or less involving restrained pregnant drivers with a gestational age of 30 weeks. For a crash speed of 40 km/h, the placental abruption area was 7.0% with a correctly positioned lap belt across the lower abdomen; it was 36.3% with the belt positioned at the umbilicus. The area of placental abruption depended on collision speed, but we found that with a correctly positioned belt it likely would not lead to negative fetal outcomes. We examined the effects on placental abruptions of reconfiguring seat belt width and force limiter setting. A wider lap belt and lower force limiter setting reduced the area of placental abruption to 3.5% and 1.1%, respectively; however, they allowed more forward movement upon collision. A 2.5 kN force limiter setting may be appropriate with respect to both forward movement and reduced placental abruption area. This study confirmed the importance of correctly using seat belts for pregnant drivers. It provides valuable evidence about improving safety equipment settings.

Biomechanical Analysis of Serious Neck Injuries Resulting from Judo.

To establish a basis for initial diagnosis and for proposing preventive measures for the serious neck injuries occasionally experienced by judo practitioners, the biomechanical mechanisms of these injuries were analyzed. Two male judo experts repeatedly threw an anthropomorphic test device (POLAR dummy) using three throwing techniques (Seoi-nage, Osoto-gari, and Ouchi-gari). The dummy's kinematic data were captured using a high-speed digital camera, and the load and moment of the neck were measured with load cells. The neck injury criterion (Nij) and beam criterion were also calculated. In Seoi-nage, the anterior and parietal regions of the dummy's head contacted the tatami (judo mat). Subsequently, most of the body weight was applied, with the neck experiencing the highest compression. However, in Osoto-gari and Ouchi-gari, the occipital region of the dummy's head contacted the tatami. Significantly higher values of both Nij (median 0.68) and beam criterion (median 0.90) corresponding to a 34.7% to 37.1% risk of neck injury with an abbreviated injury scale score ≥2 were shown in Seoi-nage than in either Ouchi-gari or Osoto-gari. In judo, when thrown by the Seoi-nage technique, serious neck injuries can occur as a result of neck compression that occurs when the head contacts the ground.

Factors Affecting the Severity of Placental Abruption in Pregnant Vehicle Drivers: Analysis with a Novel Finite Element Model.

We clarified factors affecting the severity of placental abruption in motor vehicle collisions by quantitively analyzing the area of placental abruption in a numerical simulation of an unrestrained pregnant vehicle driver at collision velocities of 3 and 6 m/s. For the simulation, we constructed a novel finite element model of a small 30-week pregnant woman, which was validated anthropometrically using computed tomography data and biomechanically using previous examinations of post-mortem human subjects. In the simulation, stress in the elements of the utero-placental interface was computed, and those elements exceeding a failure criterion were considered to be abrupted. It was found that a doubling of the collision velocity increased the area of placental abruption 10-fold, and the abruption area was approximately 20% for a collision velocity of 6 m/s, which is lower than the speed limit for general roads. This result implies that even low-speed vehicle collisions have negative maternal and fetal outcomes owing to placental abruption without a seatbelt restraint. Additionally, contact to the abdomen, 30 mm below the umbilicus, led to a larger placental abruption area than contact at the umbilicus level when the placenta was located at the uterus fundus. The results support that a reduction in the collision speed and seatbelt restraint at a suitable position are important to decrease the placental abruption area and therefore protect a pregnant woman and her fetus in a motor vehicle collision.

Ukemi Technique Prevents the Elevation of Head Acceleration of a Person Thrown by the Judo Technique 'Osoto-gari'.

Biomechanical analysis was performed to evaluate the effectiveness of mastering ukemi in preventing severe head injury in judo. One judo expert (tori) threw another judo expert (uke) with a skilled break-fall (ukemi) four times. We obtained kinematic data of uke with a digital video camera. Both translational and rotational accelerations were measured with a six-degree-of-freedom sensor affixed to uke's forehead. When Osoto-gari was performed, uke fell backward and his arm made contact with the tatami; the translational and rotational accelerations rose to peak values. The peak resultant translational and rotational accelerations were respectively 10.3 ± 1.6 G and 679.4 ± 173.6 rad/s2 (mean ± standard deviation). Furthermore, when comparing the values obtained for the judo experts with those obtained using an anthropomorphic test device (ATD: the POLAR dummy) that did not perform ukemi, both the peak resultant translational (P = 0.021) and rotational (P = 0.021) accelerations of uke were significantly lower than those for the ATD, whose head struck the tatami. Additionally, there was no significant difference among the three axis directions for either translational (ax: 7.4 ± 0.2, ay: 8.5 ± 2.1, az: 7.2 ± 0.8 G) or rotational (αx: 576.7 ± 132.7, αy: 401.0 ± 101.6, αz: 487.8 ± 66.6 rad/s2) acceleration. We confirmed that performing correct ukemi prevented the elevation of head acceleration by avoiding head contact with the tatami when a judoka is thrown by Osoto-gari. Judoka should therefore undertake intensive practice after they have acquired ukemi skills.

Mechanisms of Negative Fetal Outcome in Frontal Vehicle Colli-Sions Involving Unbelted Pregnant Drivers.

To determine the cause of negative fetal outcomes and the causative mechanism in a frontal collision, we analyzed the kinematics and mechanisms of injuries using an unbelted pregnant dummy, the Maternal Anthropometric Measurement Apparatus dummy, version 2B. Sled tests were performed to recreate frontal impact situations with impact speeds of 13, 26, and 40 km/h. Overall kinematics of the dummy were examined through high-speed video imaging. Quantitative dummy responses-such as time courses of the abdominal pressure, chest deflection, neck injury criteria (Nij), and displacement of the pelvis during impact-were also measured. The maximum abdominal pressure of 103.3 kPa was obtained at an impact speed of 13 km/h. The maximum chest deflection of 38.5 mm and Nij of 0.36 were obtained at an impact speed of 26 km/h. The highest maximum chest deflection of >40.9 mm, Nij of 0.61, and forward pelvis displacement of 478 mm were obtained at an impact speed of 40 km/h. Although the kinematics and mechanism of injuries of the dummy were different for different collision speeds, we found that unbelted pregnant drivers suffer severe or fatal injuries to the fetus even in low-speed collisions.

Biomechanical Analysis of the Head Movements of a Person Thrown by the Judo Technique 'Seoi-nage'.

The present study examined the kinematics and biomechanical parameters of the head of a person thrown forward by the judo technique 'Seoi-nage'. A judo expert threw an anthropomorphic test device (the POLAR dummy) five times. Kinematics data were obtained with a high-speed digital video camera. Linear and angular accelerations of the head were measured by accelerometers mounted at the center of gravity of the dummy's head. When Seoi-nage was performed, the dummy fell forward accompanied by contacting the anterior parietal regions of the head to the tatami, and the linear and angular accelerations of most axes reached peak values when the head contacted the tatami. Peak resultant linear and angular accelerations were 20.3 ± 9.8 G and 1890.1 ± 1151.9 rad/s2, respectively (means ± standard deviation). Peak values in linear and angular acceleration did not significantly differ between the three directional axes. Absolute angular accelerations in all axes observed in Seoi-nage were high and the resultant value was approximately equal to the already reported in Ouchi-gari, one of the predominant techniques causing judo-related acute subdural hematoma. However, the remarkable increase of linear acceleration in the longitudinal direction and/or angular acceleration in the sagittal plane, as previously reported in techniques being thrown backward (i.e., Ouchi-gari and Osoto-gari), was not detected. The likely mechanism of acute subdural hematoma caused by Seoi-nage is that a large angular acceleration causes large strains and deformations of the brain surface and subsequent rupture of cortical vessels.

Seatbelt paths of the pregnant women sitting in the rear seat of a motor vehicle.

PURPOSE: Seatbelt use during pregnancy is important to improve maternal and fetal survival after motor vehicle collisions. However, because the rear seatbelt of a motor vehicle tends to make contact with the neck, even if it is adequately used, some pregnant women sitting in the rear seat opt not to fasten the belt. The purpose of this study is to explore seatbelt-neck contact for pregnant women sitting in the rear seat of a motor vehicle. METHODS: We carried out an anthropometric study. Japanese women who were ≥30 weeks pregnant (n = 12) sat in the left side of the rear seat of a typical mid-size passenger sedan and fastened the seatbelt. Seating posture was investigated by measuring the coordinates of the anthropometric data points of the pregnant women (head, shoulder, hip joint, and knee joint). The belt path was analyzed by measuring the clearance between the belt and the sternum or navel. RESULTS: Among the 12 pregnant women at 33.9 week ± 3.3 week gestation, the shoulder belt deviated to the right side and subsequently contacted to the neck in four pregnant women (Contact group). The height of the Contact group was significantly shorter than that of Non-contact group (152.3 cm ± 3.0 cm vs. 159.0 cm ± 3.3 cm, p = 0.008). Regarding the relative position of the seatbelt to the subject's body, the distances from the top of the sternum to the center of the shoulder belt were significantly shorter in Contact group (3.9 cm ± 3.5 cm) than that in the Non-contact group (8.0 cm ± 1.6 cm, p = 0.03). However, no significant difference was found for the distance from the umbilicus to the center of the lap belt. CONCLUSION: Our findings show that because of short height and late term of pregnancy with protrusion of the abdomen, the shoulder belt deviates to the right or left, avoiding the protruded uterus, and subsequently makes contact with the neck. Seatbelt systems for rear seats need to be developed to improve passenger safety, especially for pregnant women.

Biomechanical analysis of acute subdural hematoma resulting from judo.

This study investigated biomechanical mechanisms of acute subdural hematoma caused by judo and sought preventive measures to reduce injury. A Japanese judo expert repeatedly threw an anthropometric test device using two throwing techniques, Osoto-gari and Ouchi-gari. Linear and angular accelerations of the head were measured. Both throwing techniques resulted in the dummy falling backwards, with the occipital area of the head contacting the mat, and peak linear and angular accelerations being observed when the head contacted the mat. For linear acceleration, the posterior-anterior direction showed the greatest force (41.0 ± 2.6 G using Osoto-gari, and 86.5 ±4.3 G using Ouchi-gari). For angular acceleration, values for sagittal plane rotation were greatest among the three directions measured (3315 ± 168 rad/s(2) using Osoto-gari, and 1328 ± 201 rad/s(2) using Ouchi-gari). We concluded that occipital head contact produced the most forceful longitudinal linear and sagittal plane angular accelerations; subsequent stretches and ruptures of parasagittal bridging veins resulting in acute subdural hematoma. As severe head injuries can result if a person's head comes into contact with the mat, offensive throwing techniques should be restricted to participants able to sufficiently demonstrate the Ukemi technique.

Rotational acceleration during head impact resulting from different judo throwing techniques.

Most severe head injuries in judo are reported as acute subdural hematoma. It is thus necessary to examine the rotational acceleration of the head to clarify the mechanism of head injuries. We determined the rotational acceleration of the head when the subject is thrown by judo techniques. One Japanese male judo expert threw an anthropomorphic test device using two throwing techniques, Osoto-gari and Ouchi-gari. Rotational and translational head accelerations were measured with and without an under-mat. For Osoto-gari, peak resultant rotational acceleration ranged from 4,284.2 rad/s(2) to 5,525.9 rad/s(2) and peak resultant translational acceleration ranged from 64.3 g to 87.2 g; for Ouchi-gari, the accelerations respectively ranged from 1,708.0 rad/s(2) to 2,104.1 rad/s(2) and from 120.2 g to 149.4 g. The resultant rotational acceleration did not decrease with installation of an under-mat for both Ouchi-gari and Osoto-gari. We found that head contact with the tatami could result in the peak values of translational and rotational accelerations, respectively. In general, because kinematics of the body strongly affects translational and rotational accelerations of the head, both accelerations should be measured to analyze the underlying mechanism of head injury. As a primary preventative measure, throwing techniques should be restricted to participants demonstrating ability in ukemi techniques to avoid head contact with the tatami.

Simple strategy to prevent severe head trauma in Judo.

To determine whether the use of an under-mat has an effect on impact forces to the head in Judo, a Judo expert threw an anthropomorphic test device using the Osoto-gari and Ouchi-gari techniques onto a tatami (judo mat) with and without an under-mat. Head acceleration was measured and the head injury criterion (HIC) values with or without under-mat were compared. The use of an under-mat significantly decreased (p = 0.021) the HIC values from 1174.7 ± 246.7 (without under-mat) to 539.3 ± 43.5 in Ouchi-gari and from 330.0 ± 78.3 (without under-mat) to 156.1 ± 30.4 in Osoto-gari. The use of an under-mat simply reduces impact forces to the head in Judo. Rule changes are not necessary and the enjoyment and health benefits of Judo are maintained.

Effects of seat belts worn by pregnant drivers during low-impact collisions.

OBJECTIVE: The aim of this study was to understand the injury mechanisms of pregnant drivers and associated fetal outcomes. STUDY DESIGN: Frontal and rear impact tests using a dummy representing the anthropometry of a pregnant woman were conducted. RESULTS: In frontal impact tests without a seat belt, abdominal pressure peaked at the point where the dummy contacted the steering wheel. Rear impact tests without a seat belt showed that the dummy moved forward because of rebound and contacted the steering wheel, which was avoided when a seat belt was worn. CONCLUSION: Wearing a seat belt reduces abdominal pressure or prevents contact with the steering wheel during collisions.

Experimental analysis of the relationship between simulated low-velocity rear-end collisions and fetal outcomes of pregnant rats.

Our study aimed to define the risk for a human fetus of rear-end vehicle collisions. We therefore performed drop tests using pregnant SLC Wistar rats. Pressure applied to the rat uterus and rectum at various stages of acceleration was measured. After being dropped, rats were observed throughout pregnancy. At birth, the numbers, weight and the occurrence of physical anomalies among pups were followed-up for 28 days. Uterine pressure increased exponentially from 2.1 +/- 0.3 kPa at 19-fold gravity (G) to 13.9 +/- 0.8 kPa at 92-fold G. These values are much lower than the mechanical failure level of human fetal membrane tissue or of those at risk of adverse fetal outcomes. Neither the average number of offspring per pregnant rat nor the average body weight of newborn pups differed significantly between control pregnant rats and those which had been exposed to acceleration of 46-fold or 92-fold G. Other variables such as maternal mental distress, motion effects of amniotic fluid or seatbelt-induced uterine injuries might contribute to fetal loss.

Sudden death while driving a four-wheeled vehicle: an autopsy analysis.

We retrospectively analysed forensic autopsies to resolve various issues associated with sudden natural death while driving. We collected information about the medical history, drug treatment, anthropometry and body mass index (BMI) of 34 individuals who suddenly died of natural causes while driving four-wheeled vehicles. The reasons for driving, details of the vehicle, type of collision, perspective of vehicle behaviour and types of avoidance manoeuvres were also examined. The injury severity score (ISS), the Abbreviated Injury Scale (AIS) and the degree of cardiomegaly of the driver were determined from autopsy findings. The dominant cause of death was ischemic heart disease, which closely agreed with previous findings. However, forensic signs indicated that only 20.6% of deceased drivers had attempted avoidance manoeuvres such as braking or steering before the fatal accident, which contradicts previous findings.

Analysis of seating position and anthropometric parameters of pregnant Japanese drivers.

OBJECTIVE: An anthropometric study was performed to understand the quantitative characteristics of the seating posture of Japanese pregnant drivers. METHODS: Twenty pregnant women with a mean gestation of 31.4 +/- 1.9 weeks and 20 age-matched, non-pregnant women provided written informed consent to participate in this study. A mid-sized, sedan-type passenger vehicle was used for measurement. The subjects, wearing light clothing, sat in the driver's seat of the vehicle and fastened the seatbelt after adjusting the seat to their usual driving posture. Longitudinal displacement of the slide adjuster and the reclining angle of the seat back were measured, relative to the reference position. Seating posture was investigated by measuring the coordinates of the anthropometric datum points of the drivers (head, shoulder, hip joint, knee joint, and the clearance between the steering wheel and the upper torso). RESULTS: The mean horizontal clearance between the lower rim of the steering wheel and the abdomen of the pregnant women was 146 +/- 56 mm, significantly smaller than that of the non-pregnant women (251 +/- 51 mm), due to the protrusion of the abdomen. There was no significant difference in seat adjustment position between the two groups. The height of the pregnant women and the horizontal distance from the lower rim of the steering wheel to the abdomen showed a moderate linear correlation in the pregnant group (R2 = 0.56). CONCLUSIONS: Compared to previous studies, the differences of longitudinal distance were found between American and Japanese subjects without significant differences of body heights, due to the difference of body weights and abdominal circumferences. This is the first report to analyze the seating position and anthropometric parameters of pregnant drivers in an Asian population.

Analysis of cervical injuries in persons with head injuries.

To determine which clinical factors are useful for predicting concomitant injuries of the cervical spine and cervical spinal cord in persons with head injuries, we examined the nature and mechanisms of cervical injuries. For 109 forensic autopsies of persons with head injuries, the cause of injury, mechanism of cervical injury, survival time, and anatomic injury severity (1990 revision of the abbreviated injury scale [AIS] and injury severity score) were determined. Traffic accidents were the most common cause of injuries (41.3%), followed by slips and falls (24.8%), assaults (17.4%), and falls from height (9.2%). The mean maximum AIS scores and the AIS scores of the head or neck were similar in the 4 groups. Cervical spine injuries and epidural or subdural hemorrhages of the cervical spinal cord were more common in persons dying in traffic accidents and falls from height than in persons dying in slips and falls or assaults. Cervical injuries were significantly more common in persons sustaining frontal impacts than lateral or rear impacts. The most common cervical hyperextension injuries were atlanto-occipital and atlantoaxial dislocation and injuries of the 5th intervertebral disc. Our results suggest that persons with injuries of the head due to high-energy frontal impacts should be carefully examined for concomitant cervical injuries. These findings should be helpful for decreasing preventable deaths from undiagnosed cervical injuries in head-injured persons.

A retrospective analysis of oral and maxillofacial injuries in motor vehicle accidents.

PURPOSE: To clarify the relations of the severity of oral and maxillofacial injuries from traffic accidents (TAs) to seating position and the use of restraint systems. PATIENTS AND METHODS: Hospital records were reviewed for all patients who had sustained oral or maxillofacial injuries in TAs and then were admitted to the Department of Oral and Maxillofacial Surgery, Dokkyo University School of Medicine (Tochigi, Japan), from 1994 through 2003. RESULTS: A total of 201 patients, with a mean injury severity score (ISS) of 7.9 +/- 7.6, were included in this study. Although patients with any oral or maxillofacial injury with an Abbreviated Injury Scale (AIS) score of 2 or more had extremely low ISSs, hospitalization was relatively long. The ISS and AIS score of the head or neck were significantly higher in unrestrained drivers (12.4 +/- 11.2, 1.2 +/- 1.4, respectively) than in restrained drivers (6.5 +/- 4.6, 0.4 +/- 1.0, respectively). However, AIS scores of the face were similar in unrestrained drivers (1.9 +/- 0.7) and restrained drivers (1.7 +/- 0.5). Furthermore, the incidence of maxillofacial fractures did not differ between the 2 groups. CONCLUSION: Because wearing seat belts cannot prevent all oral and maxillofacial injuries in motor vehicle occupants, both physicians and engineers must pay greater attention to the mechanisms of oral and maxillofacial injuries in TAs.

Traffic injuries of the pregnant women and fetal or neonatal outcomes.

OBJECTIVE: To investigate the relationship between pregnancy outcome and injury severity of pregnant woman in traffic accidents. METHOD: We reviewed insurance reports of traffic accidents and collected data on injuries of pregnant women and outcomes of their pregnancies. RESULT: A total of 135 pregnant women, with a mean injury severity score of 1.8+/-4.0, were involved in traffic accidents from 1994 through 2003. Injury severity score, abdominal abbreviated injury scale score were significantly higher in women whose neonates died than in women with healthy newborns. However, neither the likelihood of having been subjected to direct external forces during the accident nor injury severity differed between women with spontaneous abortions and woman with healthy newborns. CONCLUSION: Predicting abortion on the basis of maternal injury severity is difficult. Because unknown variables may contribute to fetal loss, further studies of traffic injuries are needed.