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Seat Belt Injury

Seat Belt Injuries

Seat belt injuries occur as a result of the improper use of these protective devices in restrained occupants involved in traffic accidents. Patients that sustain these injuries can have abdominal organ damage, and fractures in the sternum and spinal vertebra.


Presentation

The overall clinical picture is influenced by which sites have undergone trauma. For example, patients with a sternal fracture suffer from pain in that area. Note this injury may be accompanied by spinal and rib damage. however, intestinal trauma is not often associated with sternal fractures. Also, there should be suspicion for rare conditions such as a myocardial contusion.

Patients with bowel injuries may not exhibit signs such as abdominal pain and peritonitis on initial assessment [12]. Since the clinical manifestations may be delayed, this presents a diagnostic challenge.

Regarding vital signs, patients may present with hemodynamic stability and then deteriorate. Hence, there should be a high index of suspicion for looming emergencies. Furthermore, one study [10] observed that a systolic blood pressure below 90mm Hg was suggestive of morbidity. Other signs indicative of hemorrhage and shock are lightheadedness, dizziness, weakness, and mental status changes.

Physical exam

Tenderness and abdominal distention are among the concerning and worrisome findings on the physical exam. Furthermore, patients with the "seat belt sign" display a band of abrasions, contusions, and petechiae across the abdomen. One study [13] linked this pattern to a higher risk of abdominal trauma and the need for surgical intervention.

In addition to the abdominal exam, the clinician should evaluate for fractures and spinal cord nerve damage. Hence, musculoskeletal and neurologic examinations must also be performed.

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Workup

The clinical evaluation of the individual warrants a detailed history, a thorough physical examination with a specific focus on the abdomen, and imaging studies.

Physical exam

The patient's vitals should be monitored and serial abdominal exams must be done. Additionally, assessment of the bones and joints should also be performed.

In cases where the patient is hemodynamically unstable, there is no time for imaging as emergency laparotomy takes immediate precedence.

Imaging

The diagnostic tools for stable patients include radiography, computed tomography (CT) and focused abdominal sonography in trauma (FAST).

Regarding the CT scan, it is specific for identifying solid organ injuries although it is not sensitive for depicting bowel and mesenteric traumas.

The noninvasive FAST scan is done rapidly and can be quite useful in revealing peritoneal fluid. This test can be performed on unstable patients suspected to have abdominal trauma. Note that FAST lacks sensitivity and therefore a CT scan should be performed to confirm negative abdominal findings.

Due to the increased use of CT, diagnostic peritoneal lavage (DPL)is not frequently employed. This can be substituted in place of CT for those who are unsuitable for the latter. Additionally, the adjunct use of these 2 diagnostic studies yields sensitive results, which lead to fewer diagnostic laparotomies [14].

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Treatment

The therapeutic approach will depend on the overall clinical picture.

Hemodynamically stable

Hospital admission and serial exams are warranted for patients suspected to have abdominal injuries that have not become apparent yet. These patients present with stable vital signs and an unremarkable physical exam on initial assessment.

Hemodynamically unstable

Immediate intervention is required in this case as delay in treatment increases the risk of morbidity and mortality [12]. Moreover, abdominal injuries diagnosed within the first 6 hours are associated with better postoperative outcomes and fewer complications. Those with a delayed diagnosis are susceptible to sequelae such as sepsis, small bowel obstruction, and longer hospital stays. Note that age, other present injuries, and general health are also factors contributing to the recovery.

Fractures

Pain control and appropriate expert consultation are necessary for the management of fractures.

Overall, the treatment is focussed upon the clinical presentation of the disease and the degree of severity.

Prognosis

Patients exhibiting the seat belt sign should be admitted for close monitoring and serial physical examinations. A delay in the recognition of bowel injuries may lead to greater chance of morbidity and death [9]. Hence, if abdominal pain is emerging, this is a signal indicating an immediate need for surgical exploration [10].

With regards to better outcomes, backseat of the vehicle is usually safer than front seat [11].

Etiology

Seat belt injuries arise from the increased number traffic accidents as well as the greater compliance in the use of this devices. One of the most predominantly observed injuries is the sternal fracture. Additionally, since the seat belt has been mandated, the incidence of sternal fracture has tripled [4]. Other commonly seen injuries are subcutaneous bruising and abrasions on the chest and abdomen at the location of contact between the restraint device and the body. The improper placement of the seat belt is the main causative factor associated with this disease.

Epidemiology

Epidemiology studies report that the increased usage of seat belts has led to a reduction in fatalities. This improved mortality rate is heavily explained by the decrease in head injuries. To explain further, head trauma was observed in 50% of unrestrained individuals, yet occurred in 32% of those with seat belts. This decline was projected in the death rate, which dropped from 7% to 3.2% in high impact accidents [5].

On the other hand, there is an increase in a group of injuries known as the "seat belt syndrome," which includes lumbar fractures, damage to the intestinal viscera, and tears/perforations of the gastrointestinal tract [6]. While these occur in adults due to inappropriate placement or factors such as obesity, these injuries are more common in children secondary to improperly positioned belts [7].

Sex distribution
Age distribution

Pathophysiology

While there is a profound decline in head injuries due to seat belt use [5], the number of restrained passengers who suffer from intestinal perforations and mesenteric devascularization are increased by 2 to 3 times [5]. These types of trauma are the result of restrained passengers who undergo rapid deceleration.

Devascularization

This is a consequence of the cumulative impact of deceleration, compression, and crush injuries. The is explained best by the following mechanism: the seat belt halts the torso suddenly, but the small bowel continues to move forward. This act causes shearing trauma in the mesentery which leads to damage of the superior mesentery artery (SMA), and the loss of perfusion.

Overall, devascularization affects the small intestine more than the large bowel. This is evidenced by a study of 333 patients with blunt abdominal trauma in which there were 30 cases of small bowel devascularization versus 4 large bowel devascularization [8].

Perforation

This phenomenon is the result of compression or crush traumas. The increased pressure in the abdomen leads to obstruction of vulnerable segments such as the terminal ileum or rectum. This is usually followed by perforation.

Lumbar spine fractures

Almost 5% of seat belted occupants in traffic accidents suffer from lumbar fractures as they sustain hyperflexion of their spinal vertebrae. Patients with these fractures are likely to have seat belt syndrome.

Other

Reports have shown a multitude of other types of fractures in the seat belt population involved in traffic accidents. Such fractures may occur in the femur, radius, clavicle, etc.

Prevention

Seat belt use and its correct placement are public health concerns. Due to the serious injuries associated with the improper use of this restraint system, preventative strategies aim to educate and guide the public on the safe method to wear the seat belt.

Since inappropriately restrained children are at double the risk of sustaining serious injury in comparison to those with correct restraints, a great deal of attention focuses on the pediatric population. There is a significant amount of literature and other forms of media dedicated to counseling and teaching parents about the correct way to use the restrained devices in children according to their age.

With regards to adults, they are highly encouraged to wear seat belts, especially the three-point harnesses. Also, public health strategies provide education on how to wear seat belts as well as the importance of correct positioning. For example, the seat belt should be positioned above the femur but below the anterior superior iliac spine (ASIS). Factors such as obesity and slouching can affect this positioning.

Summary

Since the use of seat belts has become mandatory in the past decades, the utilization of this safety system has led to a reduced risk of injuries in traffic collisions [1] as well as a decreased mortality rate. However, investigations have reported that incorrect use of this protective device can cause an injury profile known as seat belt syndrome, which consists of lumbar spine fractures [2], sternal fractures, and/or intestinal damage [3]. These injuries occur as a result of improper placement of this restraint system.

The clinical presentation of seat belt injuries varies according to the type of trauma present. Patients can sustain fractures in the spinal vertebra and sternum, and serious trauma to the bowel and mesentery. Since these individuals may be hemodynamically stable and initially asymptomatic, the clinician should remain aware and suspicious of impending clinical deterioration.

Assessment includes a complete physical exam as well as monitoring of the vital signs. Stable patients should have imaging studies done to determine the presence of abdominal trauma. However, hemodynamically unstable patients usually forego imaging and undergo urgent exploratory laparotomy. Note that early diagnosis is paramount for the prevention of morbidity and mortality.

Public health measures advocate for the use of seat belt to prevent related injuries and death. Moreover, safety strategies focus on the appropriate positioning of seat belts in all individuals, especially children. Hence, there are plenty of educational resources that guide parents about age-appropriate safety devices and their method of use.

Patient Information

While seat belts are known to prevent severe injuries and death, this protective system can itself cause injuries if not worn properly. In fact, the seat belt syndrome can occur in individuals wearing seatbelts incorrectly while involved in traffic accidents. This syndrome can include serious bowel damage, fractures in the lumbar spine, fractures in the sternum, and other trauma as well.

Who is affected by these injuries?

These injuries occur in individuals who do not wear the seat belt correctly. While adults sustain seat belt damage, children are especially affected. Furthermore, children who wear seatbelts incorrectly have double the risk of injuries compared to the children who wear the seat belt properly.

What are the signs and symptoms of seat belt injuries?

The pressure of the seat belt on the abdomen can cause serious damage to the organs and the blood vessels. These patients may not have abdominal pain in the beginning but may develop it the upcoming hours. Also, when the bleeding starts, the blood pressure may be normal for a while. However, when the volume of blood loss increases, the blood pressure falls and the patient experience lightheadedness, weakness, and other similar symptoms.

The pressure of the seat belt can cause damage in the abdomen and pelvis, which can lead to bleeding in the vomit, cough, urine or stools.

The pressure of the seat belt on the chest can result in damage to the lungs and/or heart, which causes difficulty in breathing.

Also, fractures and nerve damage will result in pain and weakness.

Signs of seat belt injuries may be shown on the body through bruising, swelling, and skin discoloration.

How are these injuries diagnosed?

The clinician will perform a full physical exam to assess injuries to the abdomen, bones, etc. Also, vital signs are critical as they must be monitored very closely. If the patient's vital signs are normal, the following imaging techniques can be performed to determine the presence of organ damage:

  • X-rays
  • CT scans
  • Abdominal ultrasonography

Note that since fractures of the sternum, lumbar spine, and other bones can occur, x-rays are performed to detect these injuries.

How are they treated and managed?

It is very important to recognize that a delay in the diagnosis of abdominal trauma can result in complications and death. Hence, the clinicians must be vigilant of present trauma that has not become obvious yet. Patients that are stable are monitored closely as the medical team will record their vital signs and repeat the physical exam frequently.

Patients that present with low blood pressure are hemodynamically unstable and should be rushed to emergency surgery. The surgical team will perform an open incision in the abdomen to search for injuries and repair them.

Patients with fractures require orthopedic consultation and subsequent treatment.

How are seat belt injuries prevented?

Public health strategies aim to encourage all individuals to use seat belts and to wear them correctly. There is a lot of education material available to guide the public how to properly position the seat belts. Note that there is a special focus on children safety as they should be wearing age-appropriate seat belts.

References

Article

  1. Crandall CS, Olson LM, Sklar DP. Mortality reduction with air bag and seat belt use in head-on passenger car collisions. Am J Epidemiol . 2001;153(3):219-224.
  2. Jones HK, McBride GG, Mumby RC. Sternal fractures associated with spinal injury. J Trauma. 1989; 29(3):360-364.
  3. Arajarvi E, Santavirta S, Tolonen J. Abdominal injuries sustained in severe traffic accidents by seatbelt wearers. J Trauma. 1987;27(4):393-407.
  4. Budd JS. The effect of seat belt legislation on the incidence of sternal fractures seen in the accident department. BMJ. 1985; 291:785.
  5. Rutledge E, Thomason M, Oller D, et al. The spectrum of abdominal injuries associated with the use of seat belts. J Trauma. 1991; 31(6):820-5; discussion 825-6.
  6. Garrett JW and Braunstein PW. The seat belt syndrome. J Trauma. 1962;2:220-38.
  7. McGrath N, Fitzpatrick P, Okafor I, Ryan S, Hensey O, and Nicholson AJ. Lap belt injuries in children. Ir Med J. 2010; 103(7):216-8.
  8. Xeropotamos NS, Nousias VE, Ioannou HV, and Kappas AM. Mesenteric injury after blunt abdominal trauma. European Journal of Surgery. 2001;167(2):106-9.
  9. Fakhry SM, Brownstein M, Watts DD, et al. Relatively short diagnostic delays (<8 hours) produce morbidity and mortality in blunt small bowel injury: an analysis of time to operative intervention in 198 patients from a multicenter experience. J Trauma. 2000; 48(3):408-414.
  10. Frick EJ Jr, Pasquale MD, Cipolle MD. Small-bowel and mesentery injuries in blunt trauma. J Trauma. 1999; 46(5):920-926.
  11. Huelke DF and Compton CP. The effects of seat belts on injury severity of front and rear seat occupants in the same frontal crash. Accid Anal Prev. 1995;27(6):835-8.
  12. Asbun H, Irani H, Roe EJ, et al. Intra-abdominal seatbelt injury. J Trauma. 1990; 30(2):189-193.
  13. Chandler CF, Lane JS, Waxman KS. Seatbelt sign following blunt trauma is associated with increased incidence of abdominal injury. American Surgeon. 1997;63(10):885-888.
  14. Cha JY, Kashuk JL, Sarin EL et al. Diagnostic peritoneal lavage remains a valuable adjunct to modern imaging techniques. J Trauma. 2009;67(2):330-4; discussion 334-6.

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Last updated: 2018-06-22 07:34