Seat belt injuries and prevention

Amazoniac

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- Seat belt syndrome: Delayed or missed intestinal injuries, a case report and review of literature

"The use of seat belts has increased significantly in the last two decades, leading to a decrease in mortality from road traffic accidents (RTA). While a seat belt of good design and properly worn will prevent the occupants of a car being flung violently against the steering wheel, dashboard, or wind-screen, the force applied to the body by the restraining effect of the belt is considerable and increase the chance of intra-abdominal injuries [1]. The use of seat belts is associated with a unique injury profile collectively termed “the seat belt syndrome”. Skin abrasions of the neck, chest and abdomen – i.e., the classic seat belt sign – indicate a high chance of an internal injury."

"Seat belts have gone through evolution, with the 3 points “lap and shoulder” retractable seat belt being the latest, most efficient and most commonly manufactured. In literature, the seat belt syndrome is associated mostly with the 2 points restriction “the lap belt”. In both of the previously presented cases, patients were using the 3 points restriction.

Bruising of the anterior abdominal wall is suggested to be due to the belt acting as a fulcrum on the soft muscles of the abdominal wall. It may sometimes result in a complete cut of these muscles, which happened in our second patient. Injury to abdominal viscera has been attributed to compression between the belt and the vertebral column [3], and the intestinal ischemia is primarily due to mesenteric tears [4].

Mesenteric tears usually occur due to the shearing force applied on the mesentery, which happens while the movable intestines continue moving with the same speed of the car, although the car is decelerated by the act of the brakes (described in physics as the inertia) [5]. These tears can be so trivial that a frank intestinal ischemia would not be apparent immediately."​

- Seatbelt Injury Causing Small Bowel Devascularisation: Case Series and Review of the Literature

"The use of seatbelts has increased significantly in the last twenty years, leading to a decrease in mortality from road traffic accidents (RTA). However, this increase in seatbelt use has also led to a change in the spectrum of injuries from RTA; abdominal injuries, particularly intestinal injuries have dramatically increased with the routine use of seatbelts. Such intestinal injuries frequently result from improper placement of the “lap belt”."

"These injuries are more prevalent in the paediatric population due to ill-fitting lap belts [3]. However, they also occur in adults, particularly when a seatbelt is worn incorrectly due to suboptimal placement, inadequate securing or patient factors such as obesity and poor positioning/slouching."

"The introduction of seatbelts, and increased compliance with their use [1], has reduced mortality and changed the injury profile associated with RTAs. The reduced mortality is largely attributed to a significant reduction in head injuries with reports of 50% head injury rate in the unbelted population reduced to 32% in the belted population, and a similar reduction in mortality from 7% to 3.2% in high impact RTAs [4]. However, seatbelted occupants in RTAs have been shown to sustain significantly more intra-abdominal injuries, with a two- to three-fold increase in intestinal perforations and mesenteric devascularisation reported [4, 5]. Such injuries occur when a restrained passenger is subject to rapid deceleration."

"The mechanism of injury resulting in devascularisation differs from that of perforation. The latter results from compression or crush injury; increased intra-abdominal pressure can cause a closed-loop obstruction at susceptible areas such as the terminal ileum or rectum which leads to perforation [6]. Devascularisation injury is more commonly caused by a combination of compression, crush, and deceleration. Deceleration occurs when the stabilizing portion of an organ ceases forward motion in the torso, while the mobile body part continues to move forward; this can result in shearing injury at fixed points of attachment such as mesentery, resulting in damage and loss of blood supply (Figures 1 and 2). The ileum and jejunum are particularly at risk in this situation via their mesenteric attachment to the posterior abdominal wall, which contains the superior mesenteric vessels. In a seat-belted occupant of a car in collision, when the seatbelt stops the torso suddenly, the small bowel continues to move forward until its mesenteric attachment brings it to a stop, causing shearing of the mesentery, with damage to the superior mesenteric artery (SMA) resulting in small bowel devascularisation—this is the injury observed in all 3 of the cases presented."

"All three patients in this series had significant abdominal contusions in the distribution of the seatbelt. This finding, termed “seatbelt sign”, has been shown to be associated with significant intra-abdominal injury. Sharma et al. [11] reported that patients with a seatbelt sign were twice as likely to have a hollow viscous intra-abdominal injury and three times as likely to have a solid organ injury as those without clinical evidence of a seatbelt sign. Similarly, Chandler et al. [5] report that the clinical finding of a seatbelt sign on presentation greatly increases the likelihood of abdominal injury and the need for operative intervention, in addition to an increased risk of intestinal perforation or mesenteric damage."

"The presence of a seatbelt sign is associated with an increased likelihood of abdominal and intestinal injuries and mandates a heightened index of suspicion."

"Early diagnosis and management of intra-abdominal devascularization injuries is critical to optimizing outcomes but of course, attempting to prevent such injuries is hugely important from a public health standpoint. It is recognized that these injuries result from improper or incorrect seatbelt use. Much of the literature in this regard focuses on the paediatric population, particularly with regard to the use of age-appropriate seat belts [3]. A study which investigated the effects of seating position and appropriate restraint use on the risk of injury to children in motor vehicle crashes showed that children who were restrained inappropriately were at twice the risk of serious injury compared with those who were restrained appropriately; children without restrain were three times at risk of serious injury [19]; the same study confirmed that children in the front seat were at a 40% greater risk of injury. In the adult population, three point harnesses have been shown to be favourable over lap belts and they decrease the risk of “seatbelt syndrome” injuries. In addition to encouraging people to wear their seat belts, public health strategies should also focus on education and awareness of the importance of wearing the seat belt correctly. For a seat belt to be worn correctly it should be positioned below the Anterior Superior Iliac Spine (ASIS) and above the femur, and be secure so as to couple the occupant to the vehicle during a crash. Obesity and slouching during long journeys are common ways in which a seat belt can adapt an improper position."​

- Pelvis | Britannica

1610989299605.png

- Injuries caused by the safety belts of vehicles

"This syndrome was first defined in 1962 by Garrett and Braumstein, who described the trauma caused by the side of the belt passing over the thighs [5]. The most common injuries caused by the seat belt are superficial excoriations and ecchymosis located on the neck [6], thorax and abdomen [7], associated in about 30% of cases with injuries of internal organs [8]."

Evolution of the seat belt:
1610989336974.png

"It is no longer a simple, tear-resistant textile element that does not allow the passenger to slide forward and hit the interior of the car. The seat belt is currently a system of elements that, put together, serve the same purpose and maximize the chances of the passenger or of the driver to be protected against injuries. Functions have been implemented, such as ensuring a progressive deceleration of the body at the same rate as that of the car involved in the accident, distribution of the impact force, pressure in several areas, pressure points along the pelvis and chest, considered to be locations less sensitive to such forces which, together with the airbags, do not allow the person with the belt fastened to hit the interior of the car or to be projected out of the car. Pretensioning is currently the key element of the seat belts. Belt tensioning of the seat belt works similarly to the operation of an airbag."

"Safety systems, either the belt or the airbag, save lives when used correctly. It is important for the seat belt to be positioned along the center of the chest, ensuring a safe distance from the neck. It should never be carried under the arm or on the back. The bottom of the belt should be tight in the lap, certainly under the stomach. It should also not be very tight but not too loose. It should allow the user to perform sufficiently free movements."

"If symptoms not present beforehand occur after a car accident, such as abdominal pain, dizziness, difficulty in breathing, stiff neck, bleeding, seemingly unwarranted bruises, it is imperative to contact the doctor for the application of a therapeutic approach to injuries caused by seat belts."​

- Injuries caused by seatbelts

"The lap portion of a safety belt is designed to restrain the occupant by fixing the pelvis into the seat, with the points of contact of the belt over the iliac crests. The main cause of morbidity resulting from lap belts is ‘submarining’ of the occupant underneath the belt, allowing it to ride up over the lower abdomen. During impact, this causes the belt to apply force across the lower abdomen resulting in the seat belt syndrome and associated injuries. To combat this, antisubmarining seats are now designed to stop the occupant riding forward below the belt, by the shape of the seat. The cushion frame of the seat incorporates a ramp that slopes upward toward the front of the seat, which during a collision presses against the occupant's pelvis and thighs to help keep the lower body from sliding under the lap belt. The anti-submarining airbag fulfils a complementary role in protecting the vehicle occupant in a frontal collision. It is mounted on the front seat under the occupant’s knees, and at the point of collision inflates, holding the pelvis back against the seat."​
 

JudiBlueHen

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I had a serious wreck in 1988 in which I was stopped at a light and a large old car hit me from behind at full speed (driver apparently asleep or impaired). That impact smashed me backward and broke the seatback; then my car was propelled into the car in front of me and I was slammed into my chest seatbelt. Needless to say I had whiplash, but more to the point of this study, I suffered chest contusions from the seatbelt and could not use my arms (as to steer a car) for several weeks and could not lay on my side for 6 months due to pain in the sternum area. In those days the ER just looked for broken bones (none) and sent me home with a neck brace. But there is no doubt the seatbelt saved my life.

Long term issues - headaches, neck and upper back pain from lifting, and lots of muscle spasms in my upper abdomen from angular movements, such as sneezing while not facing directly forward.

Thanks for posting this study - anyone experiencing an accident needs further assessment after the X-rays show no broken bones.
 

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