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Pedestrian Struck: Trauma Radiology and the Car You Drive

Pedestrian Struck: Trauma Radiology and the Car You Drive. A Sedlic, MD; S Gershony, BSc; D Tso, BSc; C Chingkoe, BSc; S Nicolaou, MD . Objectives.

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Pedestrian Struck: Trauma Radiology and the Car You Drive

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  1. Pedestrian Struck: Trauma Radiology and the Car You Drive A Sedlic, MD; S Gershony, BSc; D Tso, BSc; C Chingkoe, BSc; S Nicolaou, MD

  2. Objectives • To present radiological manifestation of injuries seen in cases of pedestrians struck by motor vehicles as demonstrated by plain film, CT, and ultrasound • To introduce and describe commonly encountered injury patterns • To compare mechanism of injury and radiological findings in collisions involving different types and sizes of vehicles

  3. Outline • Introduction • Mechanism of injury and vehicle type • Patterns of Injury: • Collisions involving midsized vehicles seen as lower extremity injuries and head trauma • Injury patterns involving sport utility vehicles or light trucks with an emphasis on blunt chest and abdominal trauma. • Collisions involving small compact vehicles resulting in projection over the vehicle and secondary head and spine trauma

  4. Introduction • Pedestrian motor vehicle collisions account for 13% of all traffic injuries(1) • The mechanism of injury is complex, and patients often present with multiple traumas • Vehicle type can dictate injury pattern • Structural and design characteristics influence the mechanism of impact and resultant injury patterns. (1)Peng RY, Bongard FS. J Am Coll Surg. 1999 Oct;189(4):343-8.

  5. Injury Patterns: Sedan Type Vehicles • 85% of patients are struck laterally • Musculoskeletal injury accounts for 41.4% • Lower extremity injuries are more common than upper extremities • Most injuries are secondary to “bumper impact” Peng RY, Bongard FS. J Am Coll Surg. 1999 Oct;189(4):343-8. Simms CK, Wood DP. J. Auto Engin. 2006 May;220:1085-1100.

  6. Mechanism of Injury: Automobile Type Peng RY, Bongard FS. J Am Coll Surg. 1999 Oct;189(4):343-8.

  7. Likelihood of Injury: Sedan Type Vehicle Impact Brainard BJ, et al. Ann Emerg Med. 1989 Aug;18(8):881-3 Demetriades D, et al. J Am Coll Surg. 2004 Sep;199(3):382-7. Vives MJ, et al. J Spinal Disord Tech. 2008 Jun;21(4):281-7. *Increased incidence in elderly (>65)

  8. Spinal Injuries • Spinal injuries are not uncommon in pedestrian motor vehicle collisions • Reported in 8% of patients • Injuries distributed throughout the spine Vives MJ, et al. J Spinal Disord Tech. 2008 Jun;21(4):281-7.

  9. Head and Extremity Injuries • MSK, Head, and external injuries predominate in pedestrian motor vehicle collisions • 86.3% of all injuries sustained • Consistently reproduced finding in adult pedestrian trauma Brainard BJ, et al. Ann Emerg Med. 1989 Aug;18(8):881-3.

  10. Lower Extremity Injuries • Sedan type passenger vehicles result in lower extremity initial impact • Tibia-fibula fractures are most common • Tibia-Fibular fractures = 33.9% • Pelvis fractures = 30.4% • Femoral fractures = 27% Brainard BJ, et al. Ann Emerg Med. 1989 Aug;18(8):881-3. Image source: www.theaa.com

  11. B A C 36 yo male struck by mid-size sedan CT: intra-articular fracture involving lateral tibial plateau and fibular head Portable Radiograph demonstrates lateral plateau injury

  12. Associated Head Trauma A B • 36 y.o. male pedestrian struck with lateral tibial plateau fracture (previous slide) with associated depressed skull fracture of the left frontal bone • 20 y.o. female struck by sedan type vehicle with right fibular neck fracture (not shown) and associated right fronto-parietal skull fracture.

  13. Traumatic Brain Injury Right posterior subdural haemorrhage and left frontal contusion (white arrow) in a pedestrian stuck. Frontal hemorrhagic contusions In a 41 yo male pedestrian struck

  14. Traumatic Brain Injury Right frontal hemorrhagic contusion and a left sided epidural hematoma (green arrow) in 27 y.o. female pedestrian with no additional injury. 66 yo male pedestrian struck with bilateral subarachnoid hemorrhage (non-contrast CT)

  15. Light Truck Vehicles • Light truck vehicles (LTV) or larger vehicles includes sport utility vehicles, minivans, and pick-up trucks • LTVs have a greater mass, increased bumper height, and increased stiffness of the front bumper

  16. Light Truck Vehicle Impact • Increased bumper height relates to more severe initial impact to the upper leg and pelvis, as well as doubling of injuries to head, thorax, and abdomen • SUV impact occurs approximately 30 cm higher and much closer to the pedestrian centre of gravity (57% of height from ground) • Following impact, centre of gravity velocity is 62% of impact velocity for cars compared to 96% impact velocity for SUVs • There is also less amelioration of impact by rotation Roudsari, B., et al. Injury Prev., 2004, 10, 154–158.

  17. Light Truck Vehicle Impact and Injury Severity • Greater mass translates to higher inertia and force at the time of impact, often leading to more severe injuries. • Threefold increase in injury severity with LTV-caused accidents* • AIS > 3 more common at all speeds** • LTV-struck pedestrians have an increased risk of death for pedestrians struck by cars • 11.5% vs 4.5%*** *Roudsari, B., et al. Injury Prev., 2004, 10, 154–158. **Longhitano, D., et al. SAE paper 2005-01- 1876, 2005. ***Lefler, D. E. and Gabler, H. C. Accid. Analysis Prev., 2004, 36(2).

  18. Head injuries by LTV • Overall, large vehicles cause a slightly higher rate of head injuries at 54% in contrast to the 46% caused by small vehicles • Speed as a factor: • Cars are more likely to cause head injuries at lower speeds (18km/h) • Larger vehicles are more common culprits at higher speeds (54km/h) • Ground contact accounts for more head injuries in SUV impact (39%) compared with cars (7%) Longhitano, D., et al. SAE paper 2005-01- 1876, 2005. Liu, X. J., et al. Traff. Injury Prev., 2002, 3(31), 42. Simms CK, Wood DP. J. Auto Engin. 2006 May;220:1085-1100. Bhalla, K., et al. In Proceedings of IRCOBI Conference, Munich, Sept 2002.

  19. Head injuries by LTV 20 yo female, struck by SUV with impact to ground injuries: Left fronto-parietal epidural hematoma with an open basal skull fracture, evidenced by gas locules (arrow) within the hematoma. 40 yo pedestrian struck by light truck Right fronto-parietal depressed skull fracture.Right parietal cortical irregularity (arrow) secondary to dragging following impact by SUV

  20. Chest injuries due to LTV • Hemothoraces, pneumothoraces, and pulmonary contusions are most common intra-thoracic injuries • Traumatic aortic injuries are rare and are most commonly seen in elderly pedestrians (> 65), incidence = 1.5% • 37% chance of thoracic injury in SUVs compared with 20% for car impacts Demetriades D, et al. J Am Coll Surg. 2004 Sep;199(3):382-7.

  21. LTV Pedestrian Impact Chest Injuries 72 yo female struck by SUV Portable supine chest radiograph demonstrating a right pneumothorax seen as a deep sulcus (arrowheads) Chest CT demonstrating right pneumothorax with pulmonary contusions involving both lungs. Six contiguous rib fractures not shown

  22. LTV Impact: Thoracic Trauma CT of the same patient showing small pneumothorax (green arrow) with pulmonary contusion (blue arrow) and right hemothorax. 32 yo male struck by SUV - right sided impact Coronal reformat CT image showing a right-sided pulmonary contusion (black arrows)

  23. Abdominal and Pelvic Injuries • Vehicle acceleration tests involving cadavers show that pelvic and chest accelerations are approximately half as much as for thigh and head accelerations • Suggests that pelvis and chest are relatively protected during impact

  24. Abdominal and Pelvic Injuries • Demetriades et al. demonstrated a specific organ pattern • Liver 2.4% of all injuries • Spleen: 1.7% of all injuries • Renal: 0.8% of all injuries • Gastrointestinal: 4.1% of all injuries • Simms et al. reported 33% chance of abdominal injury for LTVs compared with 18% for cars Demetriades D, et al. J Am Coll Surg. 2004 Sep;199(3):382-7. .Simms CK, Wood DP. J. Auto Engin. 2006 May;220:1085-1100.

  25. Abdominal Trauma 29 yo female hit by SUV. Coronal formal CT showing a grade IV splenic laceration (black arrow) with hemoperitoneum (green arrows) 38 yo male hit by delivery truck. Coronal CT reformat showing a complex hepatic laceration (arrow) and extensive hemoperitoneum (green arrows)

  26. Abdominal injuries 37 yo pedestrian struck by minivan at 55 km/h Grade IV laceration of the liver (green arrows) 44 yo pedestrian struck by small truck Multiple splenic pseudoaneurysms (arrows)

  27. Abdominal injuries 50 yo pedestrian struck by an SUV Perinephric hematoma (green arrow) and active contrast extravasation (black arrow)

  28. Pelvic Trauma • High impact required for pelvic fracture • Often seen accompanying abdominal injuries • SUVs = elevated bumper height (approximately 25 cm above that of a car) results in doubling of the impulse to pelvis and upper thighs Simms CK, Wood DP. J. Auto Engin. 2006 May;220:1085-1100.

  29. Pelvic injuries Coronal CT reformat of 40 yo pedestrian struck by a light truck. Right acetabular fracture (black arrow) and liver laceration (green arrows) 36 yo pedestrian struck by an SUV. Plain radiographs show bilateral pelvic fractures

  30. Pelvic injuries 41 y.o. male struck by minivan Portable radiograph showing an intraarticular acetabular fracture (arrow) as well as widened pubis symphysis (arrowheads) 55 yo pedestrian struck Coronal CT reformat showing left superior pubic ramus fracture and adjacent hematoma

  31. Conclusion • Pedestrians struck by motor vehicles often presenting with multiple injuries • Vehicle type influences mechanism of trauma. • Mechanism of trauma dictates pattern of injuries • Sedan pedestrian impact commonly causes lower extremity trauma and associated head injury

  32. Conclusion • Light truck vehicle collisions result in significantly increased force of impact; point of impact higher • Pattern of injuries differs from sedan type vehicles • Pelvic and femoral trauma more common with increased incidence of associated blunt abdominal and thoracic trauma

  33. References • Peng RY, Bongard FS. Pedestrian versus motor vehicle accidents: an analysis of 5,000 patients. J Am Coll Surg. 1999 Oct;189(4):343-8. • Simms CK, Wood DP. Pedestrian risk from cars and sport utility vehicles- a comparitive analytical study. J. Auto Engin. 2006 May;220:1085-1100. • Brainard BJ, Slauterbeck J, Benjamin JB, Hagaman RM, Higie S. Injury profiles in pedestrian motor vehicle trauma. Ann Emerg Med. 1989 Aug;18(8):881-3. • Demetriades D, Murray J, Martin M, Velmahos G, Salim A, Alo K, Rhee P. Pedestrians injured by automobiles: relationship of age to injury type and severity. J Am Coll Surg. 2004 Sep;199(3):382-7. • Vives MJ, Kishan S, Asghar J, Peng B, Reiter MF, Milo S, Livingston D. Spinal injuries in pedestrians struck by motor vehicles. J Spinal Disord Tech. 2008 Jun;21(4):281-7. • Lefler, D. E. and Gabler, H. C. The fatality and injury risk of light truck impacts with pedestrians in the United States. Accid. Analysis Prev., 2004, 36(2). • Roudsari, B., Mock, C., Kaufmann, R., Grossman, D., Henary, B., and Crandall, J. Pedestrian crashes: higher injury severity and mortality rate for light truck vehicles compared with passenger vehicles. Injury Prev., 2004, 10, 154–158. • Longhitano, D., Henary, B., Bhalla, K., Ivarsson, J., and Crandall, J. Influence of vehicle body type on pedestrian injury distribution. SAE paper 2005-01- 1876, 2005. • Liu, X. J., Yang, J. K., and Lovsund, P. A study of influences of vehicle speed and front structure on pedestrian impact responses using mathematical models. Traff. Injury Prev., 2002, 3(31), 42. • Anderson, R. W. G., McClean, A. J., Farmer, M. J. B., Lee, B. H., and Brooks, C. G. Vehicle travel speeds and the incidence of fatal pedestrian crashes. Accid. Analysis Prev., 1997, 29(5), 667–674. • Bhalla, K., Montazemi, P., Crandall, J., Yang, J., Liu, X., Dokko, Y., Takahashi, Y., Kikuchi, Y., and Longhitano, D. Vehicle impact velocity prediction: trade offs between throw formulae, crash simulators and detailed multi-body modelling. In Proceedings of the IRCOBI Conference, Munich, September 2002.

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