Development and multi-level validation of a computational model to predict traumatic aortic injury

Traumatic aortic injury (TAI) is one of the leading causes of fatalities in blunt impact. However, there is no consensus on the injury mechanism of TAI in traffic accidents, mainly due to the complexity of occurrence scenarios and limited real-world crash data relevant to TAI. In this study, a computational model of the aorta with nonlinear mechanical characteristics and accurate morphology was developed and integrated within a thorax finite element model that included all major anatomical structures. To maximize the model's capability for predicting TAI, a multi-level process was presented to validate the model comprehensively. At the component level, the in vitro aortic pressurization testing was simulated to mimic the aortic burst pressure. Then, a sled test of a truncated cadaver was modeled to evaluate aorta response under posterior acceleration. The frontal chest pendulum impact was utilized to validate the performance of the aorta within full body model under direct chest compression. A parametric study was implemented to determine an injury tolerance for the aorta under these different loading conditions. The simulated peak pressure before aortic rupture was within the range of the experimental burst pressure. For the sled test, the simulated chest deflection and cross-sectional pressure of the aorta were correlated with the experimental measurement. No aorta injury was observed in simulated results of both sled test and chest pendulum impact, which matched the experimental findings. The present model will be a useful tool for understanding the TAI mechanisms, evaluating injury tolerance, and developing prevention strategies for aortic injuries.

The Association of Body Mass Index and Outcomes in Adult Patients with Chest Wall Injuries

BACKGROUND

Thoracic injury secondary to rib fractures following motor vehicle collisions (MVCs) significantly contribute to morbidity and mortality. While obesity has reached epidemic proportions, little is known regarding how BMI impacts outcomes in MVCs. The aim of this study was to examine how BMI impacts outcomes in MVC patients with rib fractures.

METHODS

The ACS-TQIP Database was utilized to evaluate adult MVC patients with ≥3 rib fractures. Patients with a non-thoracic AIS ≥3 were excluded, to focus on chest injuries. Patients were sorted according to the presence or absence of flail chest injuries and BMI into groups with a low (<15), intermediate (15-24), or severe (≥25) ISS.

RESULTS

Overweight and obese patients in the non-flail cohort had decreased odds of pneumothorax in all ISS groups (P < 0.05). Overweight (P = 0.049) and obese (P = 0.011) patients in the low ISS non-flail cohort had decreased odds of splenic laceration. In the non-flail cohort, obese patients with a low and intermediate ISS had decreased odds of pulmonary contusion (P < 0.01). Obese patients in the low and intermediate ISS non-flail cohorts had increased odds of PE (P < 0.05). In both the flail and non-flail cohorts, obese patients with an intermediate ISS had decreased odds of liver laceration (P < 0.05), as well as a longer HLOS, ICU-LOS, and mechanical ventilation time (P < 0.01).

CONCLUSION

Obesity affects associated injuries, complications, and hospital outcomes in a complex way after MVC related chest wall trauma. Thus, the effect of BMI should be taken into consideration when assessing and treating obese MVC trauma patients.

Thoracic Trauma: Aortic Injuries

Thoracic aortic injuries caused by high impact trauma are life-threatening and require emergent diagnosis and management. With improvement in the acute care services, an increasing number of such injuries are being managed such that patients survive to undergo definitive therapies. A high index of clinical suspicion is required to order appropriate imaging. Computed tomography angiography is used to classify the injuries and guide treatment strategy. While low-grade injuries might be managed conservatively, high-grade injuries require urgent surgical or endovascular intervention. Over the past decade, endovascular repair of the thoracic aorta with or without a surgical bypass has become the preferred treatment with reduced mortality and morbidity. Rapid advancements in the stent graft technology have reduced the anatomic barriers to endovascular therapy and increased the confidence of the operators. Detailed planning prior to the procedure, understanding of the anatomy, correct choice of hardware, and adherence to technical protocol are essential for a successful endovascular procedure. These patients are often young and the limited data on the long-term outcome of aortic stent grafts make a case for a robust follow-up protocol.

The influence of sample geometry and size on porcine aortic material properties from uniaxial tensile tests using custom-designed tissue cutters, clamps and molds

The aim of this study was to identify the influence of specimen geometry and size on the results of aortic uniaxial tensile tests using custom-designed tissue cutters, clamps and molds. Six descending thoracic aortas from pigs were used for rectangular sample tests, in which the circumferential and axial specimens had widths of 6 mm, 8 mm and 10 mm. The other six aortas were used for the dog-bone-shaped sample tests and were punched into circumferential, axial and oblique specimens with widths of 2 mm, 4 mm and 6 mm. We performed uniaxial tensile tests on the specimens and compared the test results. The results showed that mid-sample failure occurred in 85.2% of the dog-bone-shaped specimens and in 11.1% of the rectangular samples, which could be caused by Saint-Venant’s principle. Therefore, rectangular specimens were not suitable for aortic uniaxial tensile testing performed until rupture. The results also showed that the size effect of the aorta conformed to Weibull theory, and dog-bone-shaped specimens with a width of 4 mm were the optimal choice for aortic uniaxial tensile testing performed until rupture.

Die traumatische Aortenruptur

Verkehrsunfälle sind für den größten Teil der traumatischen Aortenrupturen verantwortlich, meist zusammen mit weiteren schweren Begleitverletzungen. Die prähospitale Sterblichkeit ist hoch. Bei Verdacht auf eine beteiligte Aortenverletzung, aufgrund eines hohen traumatic aortic injury scores, ist eine Computertomographie durchzuführen. Es erfolgt eine Triage der Verletzungen, und die Versorgungspriorität der Aorta richtet sich nach dem Schweregrad der Aorten- und Begleitverletzungen sowie dem Zustand des Patienten. Bis zur definitiven Versorgung der aortalen Läsion muss der Blutdruck konsequent gesenkt werden. Grad I und II können in Einzelfällen unter enger Kontrolle inital konservativ gemanagt werden. Grad III (gedeckte Ruptur) und Grad IV (freie Ruptur) benötigen eine raschestmögliche Versorgung (interventionell, chirurgisch). In ausgesuchten Fällen kann auch eine verzögerte Versorgung günstig sein.

Als bevorzugte Versorgungsform hat sich die interventionelle Stentgrafttherapie etabliert.

Biomechanics of aortic wall failure with a focus on dissection and aneurysm: A review

Aortic dissections and aortic aneurysms are fatal events characterized by structural changes to the aortic wall. The maximum diameter criterion, typically used for aneurysm rupture risk estimations, has been challenged by more sophisticated biomechanically motivated models in the past. Although these models are very helpful for the clinicians in decision-making, they do not attempt to capture material failure. Following a short overview of the microstructure of the aorta, we analyze the failure mechanisms involved in the dissection and rupture by considering also traumatic rupture. We continue with a literature review of experimental studies relevant to quantify tissue strength. More specifically, we summarize more extensively uniaxial tensile, bulge inflation and peeling tests, and we also specify trouser, direct tension and in-plane shear tests. Finally we analyze biomechanically motivated models to predict rupture risk. Based on the findings of the reviewed studies and the rather large variations in tissue strength, we propose that an appropriate material failure criterion for aortic tissues should also reflect the microstructure in order to be effective. STATEMENT OF SIGNIFICANCE: Aortic dissections and aortic aneurysms are fatal events characterized by structural changes to the aortic wall. Despite the advances in medical, biomedical and biomechanical research, the mortality rates of aneurysms and dissections remain high. The present review article summarizes experimental studies that quantify the aortic wall strength and it discusses biomechanically motivated models to predict rupture risk. We identified contradictory observations and a large variation within and between data sets, which may be due to biological variations, different sample sizes, differences in experimental protocols, etc. Based on the findings of the reviewed literature and the rather large variations in tissue strength, it is proposed that an appropriate criterion for aortic failure should also reflect the microstructure.

Traumatic aortic injury presenting to an adult major trauma centre

Introduction

Traumatic aortic injury is an uncommon condition. Timely diagnosis may enable early haemostatic resuscitation, essential to prevent worsening of the injury prior to definitive management. The aim of this study was to assess the utility of initial vital signs and presenting clinical characteristics to confirm or rule out aortic injury.

Methods

A retrospective review of patients from The Alfred Trauma Registry was conducted. Patients presenting between January 2006 and July 2014 and diagnosed with aortic injury were identified. Demographics and presenting clinical characteristics were extracted. Sensitivity of individual clinical variables for the detection of aortic injury was calculated.

Results

There were 77 patients identified with aortic injury, with an in-hospital mortality rate of 19.5% (95% CI: 10.6–28.3%). Of these, 68 (88.3%) patients presented after high-energy blunt mechanisms. Clinical signs and early chest X-ray findings were poorly sensitive to detect aortic injury. Patients who presented with hypotension had a greater severity of aortic injury, more commonly had associated abnormal investigation findings and were more likely to require blood products and inotropic agents (p < 0.05). However, sensitivity of initial hypotension to rule out aortic injury was 39.0% (95% CI: 28.1–49.9%).

Conclusions

The diagnosis of aortic injury was uncommon in hospital. Most injuries were secondary to high-velocity road traffic crashes or high falls. Clinical signs were not adequately sensitive to be used for the exclusion of aortic injury. We recommend a high degree of clinical suspicion and liberal imaging among cases where aortic injury is possible.

Case Report of Traumatic Aortic Disruption: A Lethal Injury Requiring Rapid and Accurate Diagnosis to Lower Mortality

Traumatic aortic disruption is an uncommon but frequently emphasised condition in trauma management in the emergency department. We report a case in which a middle aged woman was hit by a moving vehicle, sustaining multiple severe injuries. Multidetector computed tomography revealed an unexpected but potentially fatal condition – traumatic aortic disruption. A pseudoaneurysm was detected over the aortic arch. In view of the multiple trauma, she was put on conservative treatment. Traumatic aortic disruption should be borne in mind during the emergency evaluation and management of unstable trauma victims, especially those with significant trauma mechanisms. Radiological evaluation plays an important diagnostic role.

Blunt Force Trauma in Veterinary Forensic Pathology

Veterinary pathologists commonly encounter lesions of blunt trauma. The development of lesions is affected by the object’s mass, velocity, size, shape, and angle of impact and by the plasticity and mobility of the impacted organ. Scrape, impact, and pattern abrasions cause localized epidermal loss and sometimes broken hairs and implanted foreign material. Contusions are best identified after reflecting the skin, and must be differentiated from coagulopathies and livor mortis. Lacerations—traumatic tissue tears—may have irregular margins, bridging by more resilient tissue, deviation of the wound tail, crushed hairs, and unilateral abrasion. Hanging or choking can cause circumferential cervical abrasions, contusions and rupture of hairs, hyoid bone fractures, and congestion of the head. Other special forms of blunt trauma include fractured nails, pressure sores, and dog bites. Ocular blunt trauma causes extraocular and intraocular hemorrhages, proptosis, or retinal detachment. The thoracic viscera are relatively protected from blunt trauma but may develop hemorrhages in intercostal muscles, rib fractures, pulmonary or cardiac contusions or lacerations with subsequent hemothorax, pneumothorax, or cardiac arrhythmia. The abdominal wall is resilient and moveable, yet the liver and spleen are susceptible to traumatic laceration or rupture. Whereas extravasation of blood can occur after death, evidence of vital injury includes leukocyte infiltration, erythrophagocytosis, hemosiderin, reparative lesions of fibroblast proliferation, myocyte regeneration in muscle, and callus formation in bone. Understanding these processes aids in the diagnosis of blunt force trauma including estimation of the age of resulting injuries.

CT Chest with IV Contrast Compared with CT Angiography after Blunt Trauma

Blunt aortic injury (BAI) after chest trauma is a potentially lethal condition. Rapid diagnosis is important to appropriately treat patients. The purpose of this study was to compare CT with intravenous contrast (CTI) to CT with angiography (CTA) in the initial evaluation of blunt chest trauma patients. This was a retrospective review of all blunt trauma patients who received a CTI or CTA during the initial evaluation at an urban Level I trauma center from January 1, 2010 to December 31, 2013. Two-hundred and eighty-one trauma patients met inclusion criteria. Most, 167/281 (59%) received CTI and 114/281 (41%) received CTA. There were no differences between cohorts in age, gender, initial heart rate, systolic blood pressure, and Glasgow Coma Scale in emergency department. Mortality rates were similar for CTI and CTA (4% vs 8%, P = 0.20). CTI identified an injury in 54 per cent compared with 46 per cent in CTA ( P = 0.05). Overall, 2 per cent of patients had BAI with similar rates in CTI and CTA (2% vs 2%, P = 0.80). BAI was not missed using either CTI or CTA. Trauma patients studied with CTI had similar diagnostic findings as CTA. CTI may be preferable to CTA during the initial assessment for possible BAI because of a single contrast injection for whole body CT.

The usefulness of post-mortem CT angiography in injuries caused by falling from considerable heights: three fatal cases

OBJECTIVE

Post-mortem computed tomography is a diagnostic tool forming part of the arsenal available to forensic pathologists today. In addition to its usefulness in detecting bone lesions, which has long been recognized, this technique has nowadays been enhanced by the development of CT angiography. The role of multiphase post-mortem computed tomography angiography (multiphase PMCTA) is primordial, improving detection of solid organ lesions and permitting vascular lesions to be visualized directly.

MATERIAL AND METHODS

Our paper presents a series of three deaths by falling from a considerable height recorded since the beginning of 2012. We report the usefulness of PMCTA and the various mechanisms involved in the trauma.

RESULTS

Most of the lesions were diagnosed by both PMCTA and autopsy, including the rare lesions, but the peripheral bone lesions and the hemopneumatocele were diagnosed only by PMCTA, while dislocation of vertebrae and the testicular fractures were detected solely by autopsy.

CONCLUSION

PMCTA is a new, minimally-invasive technique which, combined with autopsy, provides better visualization and detection of certain lesions, particularly in the case of death by falling from a great height.

Laceration of the Aorta: An Autopsy Series

Of 145 autopsies on subjects of impact trauma, 35 had lacerations of the aorta located as follows: proximal aorta ( 5 ), isthmus (22), and descending aorta ( 11 ) (three subjects had lacerations of the isthmus and the descending aorta). Four of the five lacerations of the proximal aorta ruptured into the pericardial sac. All lacerations at the isthmus were full thickness. Five were double, parallel, adjacent lacerations, of which only one was circumferential. Three of the 22 also had intimal tears of the descending aorta. One of the 22 lacerations was tamponaded and did not rupture into a body cavity. In eight, rupture and bleeding occurred into both pleural cavities, whereas 12 had rupture only into the left pleural cavity. Fourteen of the 22 had evidence of transient tamponade in the form of a mediastinal hematoma. Of the 11 subjects with lacerations of the descending aorta, one had only intimal tears. The other ten had full thickness lacerations that were located throughout the descending aorta. Four of the ten had more than one aortic laceration. Six of the total 11 had a vertebral dislocation. Three of the ten also had a laceration at the isthmus. Severe wounds of the head and thoracoabdominal viscera other than the aorta were common. Most subjects died at the scene.

Novel to this study are the explicit descriptions of 1) aortic lacerations involving less than the circumference of the aorta, 2) aortic lacerations that are double, and 3) the tendency for double lacerations to be less than circumferential.

Trend of management of traumatic thoracic aortic injuries in a single center

The purpose of this study was to review the shift in the trend of management and mid-term outcomes of all patients who sustain thoracic aortic injury. A Retrospective analysis was performed of all patients sustaining blunt thoracic aortic trauma admitted to our unit. Forty-seven patients were presented with injury to the thoracic aorta following blunt chest injury. Ten patients underwent open surgical repair of their thoracic aortic injury. The mean age ± SD (range) was 29.4 ± 7.9 years (18-41) with a mean Injury Severity Score (ISS) of 41 ± 14.7 (25-75). Fifteen patients underwent thoracic endovascular repair for blunt aortic transections with a mean age of 35.1 ± 14.5 years (17-65), mean ISS of 40.8 ± 13.9 (20-75) and an average length of hospital stay of 25.6 ± 14.5 days (3-77). The mean aortic diameter proximal to the aortic injury was 23.46 ± 3.02 mm (19-28) with a mean aortic angulation of 58.46° ± 17.73 (44-80°). The mean oversizing was 24.4 ± 5.4% (17-32%). At our institution, there has been a paradigm shift in the emergent repair of blunt thoracic aortic injury from open surgery to endovascular repair. Oversizing of the stent-graft did not translate to a poorer outcome.

[Endovascular treatment of traumatic ruptures of the thoracic aorta]

Traumatic rupture of the descending aorta is an acute life-threatening event. The most common cause is deceleration trauma resulting in a sudden stretching of the aortic isthmus as for example in car and motorcycle accidents and falls from a great height. Exemplified by a case report of a multiply injured 57-year-old male the diagnostic pathways, therapy and postoperative complications are presented.

Vascular trauma in geriatric patients: a national trauma databank review

BACKGROUND

The epidemiology of vascular injuries in the geriatric patient population has not been described. The purpose of this study was to examine nationwide data on vascular injuries in the geriatric patients and to compare this with the nongeriatric adult patients with respect to the incidence, injury mechanisms, and outcomes.

METHODS

Geriatric patients aged 65 or older with at least one traumatic vascular injury were compared with an adult cohort aged 16 years to 64 years with a vascular injury using the National Trauma Databank version 7.0.

RESULTS

During the study period, 29,736 (1.6%) patients with a vascular injury were identified. Of those, geriatric patients accounted for 7.6% (2,268) and the nongeriatric adult patients accounted for 83.1% (n=24,703). Compared with the nongeriatric adult patients, the geriatric vascular patients had a significantly higher Injury Severity Score (26.6±17.0 vs. 21.3±16.7; p<0.001) and less frequently sustained penetrating injuries (16.1% vs. 54.1%; p<0.001). The most commonly injured vessels in the elderly were vessels of the chest (n=637, 40.2%), including the thoracic aorta and innominate and subclavian vessels. The overall incidence of thoracic aorta injuries was significantly higher in geriatric patients (33.0% vs. 13.9%; p<0.001) and increased linearly with progressing age. After adjusting for confounding factors, geriatric patients demonstrated a fourfold increase in mortality following vascular injuries (adjusted odds ratio, 3.9; 95% confidence interval, 3.32-4.58; p<0.001).

CONCLUSION

Vascular trauma is rare in the geriatric patient population. These injuries are predominantly blunt, with the thoracic aorta being the most commonly injured vessel. Although vascular injuries occur less frequently than in the nongeriatric cohort, in the geriatric patient, vascular injury is associated with a fourfold increase in adjusted mortality.

Pressure waves in the aorta during isolated abdominal belt loading: the magnitude, phasing, and attenuation

While rupture of the aorta is a leading cause of sudden death following motor vehicle crashes, the specific mechanism that causes this injury is not currently well understood. Aortic ruptures occurring in the field are likely due to a complex combination of contributing factors such as acceleration, compression of the chest, and increased pressure within the aorta. The objective of the current study was to investigate one of these factors in more detail than has been done previously; specifically, to investigate the in situ intra-aortic pressure generated during isolated belt loading to the abdomen. Ten juvenile swine were subjected to dynamic belt loads applied to the abdomen. Intraaortic pressure was measured at multiple locations to assess the magnitude and propagation of the resulting blood pressure wave. The greatest average peak pressure (113.6 +/- 43.5 kPa) was measured in the abdominal aorta. Pressures measured in the thoracic aorta and aortic arch were 70 per cent and 50 per cent, respectively, that measured in the abdominal aorta. No macroscopic aortic trauma was observed. To the authors' knowledge the present study is the first one to document the presence, propagation, and attenuation of a transient pressure wave in the aorta generated by abdominal belt loading. The superiorly moving wave is sufficient to generate hydrostatic and intimal shear stress in the aorta, possibly contributing to the hypothesized mechanisms of traumatic aortic rupture.

Chest impact experiments aimed at producing aortic rupture

There are a number of proposed mechanisms of traumatic aortic rupture. These experiments involved three different chest impacts that may be associated with aortic rupture. Eleven unembalmed cadavers were repressurized and impacted by a 24-34 kg mass at 8.6-14.9 m/sec. Three impact orientations were studied with the torso axis: (1) 30-45° up from horizontal and impact 28-45° clockwise of the midsagittal axis, (2) 105-130° up from horizontal and impact 15° counterclockwise, and (3) 75° up from horizontal and impact 15° counterclockwise. Spinal acceleration was measured at T1, T8, and T12 and chest compression was determined by high-speed video. Detailed autopsy determined injuries. Impact loads averaged 9.65 ± 2.45 kN and resulted in 52.8 ± 5.4% chest compression and 3.53 ± 0.94 m/sec Viscous response. The resultant spinal acceleration was 124.5 ± 105.4 g at T1, 141.3 ± 80.5 g at T8 and 89.3 ± 39.1 g at T12. The severity of impact resulted in multiple rib fractures and severe chest injury averaging AIS = 4.2 ± 1.0. There were four cases of heart laceration and one transection of the ascending aorta 20 mm from the cusp of the aortic valve. The impacts were severe enough that aortic rupture was expected; however, only one occurred. In retrospect, the position of the heart and aorta in the upright cadaver may not have been representative of the position during human injury, thus reducing the incidence of aortic rupture in these experiments.

Brain-stem laceration and blunt rupture of thoracic aorta: is the intrapleural bleeding postmortem in origin?: an autopsy study

Some of the fatally injured car occupants could have had both blunt rupture of thoracic aorta with great amount of intrapleural blood, and pontomedullar laceration of brain-stem as well, with both injuries being fatal. The aim of this study was to answer if all intrapleural bleeding in these cases was antemortem, or the bleeding could also be partially postmortem. We observed the group of 66 cases of blunt aortic rupture: 21 case with brain-stem laceration, and 45 cases without it. The average amount of intrapleural bleeding in cases without brain-stem laceration (1993 ± 831 mL) was significantly higher than in those with this injury (1100 ± 708 mL) (t = 4.252, df = 64, P = 0.000). According to our results, in cases of the thoracic aorta rupture with concomitant brain-stem laceration, the amount of intrapleural bleeding less than 1500 mL, should be considered mostly as postmortem in origin, and in such cases, only the brain-stem injury should be considered as cause of death.

Characteristics of chest injury in falls from heights

This study included 660 victims injured due to high fall. All cases are with injuries caused by the free-fall model of high fall. The range of the heights was from 0 to 70 m. The sample was divided into three groups of growing height: low falls up to 7 m, high falls from 7 to 30 m, and very high falls above 30 m. Statistical analysis was performed using two way ANOVA according to Scheirer-Ray-Hare in complete uneven block. Males were 71% (469), females 29% (191). In the analyzed sample, apart from the height of fall, the number of accidents is about 44% (290 cases) and suicides about 56% (370 cases). Thirty six percent, i.e., 238 of 660 victims had consumed alcohol before death (alcoholemia >0.5 per thousand). The objective of our study was to analyze characteristics of chest injuries made by falling from a height. The frequency of thoracic injuries is statistically significantly related to the height of fall (p<0.05); it increases constantly in falls from heights beyond 3m, so that the rib fractures were present in all falls from heights beyond 40m. The aortic ruptures were found in 21%, and the heart injuries in 16% of all cases. The frequency of aortic and heart ruptures was not statistically significantly related to the height of fall (p>0.05). A rupture of the aorta was the most commonly located on its arch (82%). The heart ruptures were the most commonly located on the atrial posterior wall (70%).

Mechanisms of traumatic rupture of the aorta and associated peri-isthmic motion and deformation

This study investigated the mechanisms of traumatic rupture of the aorta (TRA). Eight unembalmed human cadavers were tested using various dynamic blunt loading modes. Impacts were conducted using a 32-kg impactor with a 152-mm face, and high-speed seatbelt pretensioners. High-speed biplane x-ray was used to visualize aortic motion within the mediastinum, and to measure deformation of the aorta. An axillary thoracotomy approach was used to access the peri-isthmic region to place radiopaque markers on the aorta. The cadavers were inverted for testing. Clinically relevant TRA was observed in seven of the tests. Peak average longitudinal Lagrange strain was 0.644, with the average peak for all tests being 0.208 +/- 0.216. Peak intraluminal pressure of 165 kPa was recorded. Longitudinal stretch of the aorta was found to be a principal component of injury causation. Stretch of the aorta was generated by thoracic deformation, which is required for injury to occur. The presence of atherosclerosis was demonstrated to promote injury. The isthmus of the aorta moved dorsocranially during frontal impact and submarining loading modes. The aortic isthmus moved medially and anteriorly during impact to the left side. The results of this study provide a better understanding of the mechanisms associated with TRA, and can be used for the validation of finite element models developed for the examination and prediction of TRA.

Acute traumatic aortic injury: imaging evaluation and management

Despite recent advances in prehospital care, multidetector computed tomographic (CT) technology, and rapid definitive therapy, trauma to the aorta continues to be a substantial source of morbidity and mortality in patients with blunt trauma. The imaging evaluation of acute aortic injuries has undergone radical change over the past decade, mostly due to the advent of multidetector CT. Regardless of recent technologic advances, imaging of the aorta in the trauma setting remains a multimodality imaging practice, and thus broad knowledge by the radiologist is essential. Likewise, the therapy for acute aortic injuries has changed substantially. Though open surgical repair continues to be the mainstay of therapy, percutaneous endovascular repair is becoming commonplace in many trauma centers. Here, the historical and current status of imaging and therapy of acute traumatic aortic injuries will be reviewed.

Motor vehicle collisions and their demographics: a 5-year retrospective study of the Hamilton-Wentworth Niagara region

This retrospective study examined population demographics associated with motor vehicle collision (MVC) fatalities over a 5-year period in the Hamilton-Wentworth Niagara region. Variables were drawn from the five factors proposed by Fierro (1) for investigating deaths caused by transportation: human, chemical, environmental, vehicular, and highway. Factors analyzed included age, gender, position to the vehicle, site(s) of injury, toxicology, environmental contributors, and vehicular findings. From 1999 to 2004, there were 321 MVC fatalities that primarily involved males 20 to 29 years of age and commonly drivers or pedestrians. Cars and trucks were the most frequent vehicles. Fatalities occurred most often on local and regional roads on Fridays and Sundays between 6 pm and 6 am. Mechanical failure and weather conditions were not significant contributors. Toxicological analyses (275/321) were performed on the majority of the study population. Ethanol was present in isolation and with other substances, especially cannabis, mostly in male drivers 20-59 years of age.

Evaluation of aortic injury in driver fatalities occurring in motor vehicle accidents in the State of Maryland for 2003 and 2004

Incorporating epidemiological and pathologic factors, a retrospective analysis of aortic injury and driving fatalities was conducted. To better understand the mechanism of injury, data were compiled for decedent demographics, autopsy and toxicology findings, and accident circumstances, with emphasis on directional impact. Review of the autopsy files of the Office of the Chief Medical Examiner in the State of Maryland in 2003 and 2004, identified 150 cases of aortic injury recorded in 537 autopsied drivers. Aortic lacerations occurred in 96% of the cases with aortic injury, two thirds of which were complete or near complete transections. A large percentage of cases involved a side impact collision. Consistent with extant research on frontal and lateral impacts, the majority of aortic injuries occurred at the ligamentum arteriosum. Also, the mechanism of aortic injury seems to be similar for side and frontal impact collisions, involving a combination of rapid deceleration forces along with chest and/or upper abdominal compression. This study emphasizes the importance of side impact collisions as a cause of aortic injury. Aortic lacerations have a high mortality rate and better motor vehicle design may prevent this type of injury.

Traumatic rupture of thoracic aorta in real-world motor vehicle crashes

OBJECTIVE

Traumatic rupture of thoracic aorta (TRA) was reported in the literature to be a major cause of death in motor vehicle crashes. This study aims at evaluating the most relevant risk factors of TRA. It also aims at analyzing the types of TRA as a function of car crash conditions and rib cage fractures.

METHODS

In-depth crash data collected from 1998 to 2006 as part of the Co-operative Crash Injury Study (CCIS) were retrospectively investigated to assess frontal, near-side, and far-side injury risks. This database includes 15,074 occupants with individual detailed autopsy reports. Multivariate statistical analyses were performed. The influence of the following variables on TRA occurrence was studied: gender and age of the involved occupant, ETS, compartment intrusion, and restraint system. Features of TRA and rib cage fractures were described thanks to autopsy data.

RESULTS

Although TRA occurred in only 1.2% of all occupants, TRA victims accounted for 21.4% of all fatalities. The incidence of TRA was found twice higher in side impacts (2.4%) than in frontal ones (1.1%). TRA injury risk increased with ETS, intrusion, and age and decreased with the absence of intrusion regardless of the impact direction. It also decreased for belted occupants in frontal impacts. Except for the site of injury, the TRA features were similar whatever the crash conditions. The multiple ribs fractures were the most common injuries associated with TRA (79.1%) and TRA victims with uninjured or slightly injured (AIS 1) rib cage were significantly younger (p < 0.0001) than other TRA victims. Whatever the impact type, the TRA victims sustained mostly bilateral rib fractures (68%). Results also emphasized a close relationship between the principal direction of force and the body side with more fractured ribs. However, whatever the impact type, the aortic injury site or the side of the thorax, fractures concerned mainly the 2nd up to the 7th ribs of TRA victims.

CONCLUSIONS

This study emphasized four main variables influencing the TRA occurrence: ETS, compartment intrusion, age, and seat belt use. The results suggested that the injury site may be different depending on the occupant or the impact type. However, the typical TRA, i.e., a partial or complete aorta transection within the peri-isthmic region, affected any occupant independently of age and impact type. The high frequency of bilateral rib cage fractures observed in TRA victims and the significant influence of intrusion on TRA occurrence emphasized that the aortic injury mechanism mainly involves a severe direct chest impact or compression.

A novel model of blunt thoracic aortic injury: a mechanism confirmed?

BACKGROUND

There is no consensus on the mechanism of traumatic injury to the thoracic aorta and no reproducible animal model. Advances in injury scene analysis suggest that lateral and oblique force vectors cause aortic injury. We hypothesized that the spectrum of aortic injury could be reproduced in an animal model by application of an obliquely directed load to the pressurized aorta.

METHODS

Graded air impulses of 80, 100, 110, and 120 pounds per square inch (PSI) were delivered to the descending thoracic aorta of 19 swine with a novel pneumatic device. Aortic isthmus strain was recorded with microminiature probes. Gross and microscopic injury was recorded with digital photography.

RESULTS

The spectrum of human aortic injury was reproduced in this model. Deep injuries to the aortic media were common. The majority of injuries occurred within the region of the isthmus. Impulse pressure of 120 PSI caused transections, whereas lower impulse pressure resulted in less severe injuries. Aortic isthmus strain was greater in the animals exposed to 120 PSI than those receiving lower PSI (19.6 +/- 4.9% vs. 8.7 +/- 2.5%, p = 0.067).

CONCLUSIONS

Direct loading of the pressurized descending thoracic aorta causes isthmus injury secondary to aortic wall strain. Deep medial lesions are common and could propagate soon after injury to form pseudoaneurysms. A critical load is required to cause complete uncontained transection with exsanguination, which may have relevance to injury scene death.

Mechanisms of Aortic Blunt Rupture in Fatally Injured Front-Seat Passengers in Frontal Car Collisions

We tried to explain the mechanisms of the aortic blunt ruptures in fatally injured drivers and front passengers, unrestrained by seatbelts, by analyzing the frequencies of both aortic ruptures and concomitant injuries to 12 organs and body regions. The sample consisted of 393 subjects: 251 drivers and 142 front passengers (325 male and 68 female passengers, the mean age 41.0 +/- 15.5). The total number of the complete blunt aortic ruptures in the sample was 116 (80 in the drivers and 36 in the front passengers). The weakest part of the aorta seems to be the isthmus (47 isthmus ruptures in the drivers and 27 in the front passengers). The statistically significant concomitant injured organs and body regions with the aortic ruptures were the liver, the sternum, and the diaphragm in the car drivers and the head and the neck in the front passengers. According to these results, the mechanisms of thoracic aorta rupture are different for fatally injured drivers and front passengers. For car drivers, they are associated and simultaneous with both thoracic and abdominal compression due to deceleration of the body at the moment when the driver's body slides forward and flexes across and against the steering wheel. For the front passengers, the mechanism is the caudorostral hyperextension of the thoracic aorta at the moment when the body is stopped by a dashboard, but the head continues forward with great velocity: the carotid vessels pull the aortic arch forward at the same time as the intercostal arteries fix the thoracic part of the aorta and pull it downwards.

Computer simulation and validation of the Archimedes Lever hypothesis as a mechanism for aortic isthmus disruption in a case of lateral impact motor vehicle crash: a Crash Injury Research Engineering Network (CIREN) study

OBJECTIVES

Can aortic isthmus disruption occurring in a lateral motor vehicle crash (LMVC) be explained by the Archimedes Lever Hypothesis, where the intrathoracic aorta, super-pressurized by the thoracic impact force, functions as a rigid lever system? The long arm of this lever system is the proximal aorta-aortic arch, the short arm is the aortic isthmus fixed distally at the descending aorta, and the fulcrum is at the great vessels, especially the left subclavian artery.

METHODS

The theory was tested by a simulation technique using a computer-based finite element numerical model system. This simulation model included the dynamics of the crashed vehicles, the direction of force impact, and the structure of the thorax and intrathoracic viscera, including the entire intrathoracic aorta. The specific patient whose data were entered into the model was chosen from a study of 34 LMCV aortic injuries (AIs). The model was constrained by patient and vehicle data from this surviving case.

RESULTS

Three sequential lateral thoracic levels impacted by the vehicle side structures were selected. At each level, the maximum mean intra-aortic pressure was 50 to 100 ms after impact, the structure dynamics of the actual crash and the resultant vehicle deformation were simulated; only when the lateral impact was induced in a transverse plane including the first 4 ribs at the level of the aortic arch/isthmus system, with intra-aortic pressures from 200 to 500 mm Hg, were AI-compatible stresses and deformations in the aortic wall achieved at the isthmus.

CONCLUSIONS

In LMVC AI, the simulation suggests that the aorta functions as an Archimedes Lever System in which the magnified force mediated by the long lever arm produces sufficient strain on the short lever arm to rupture the aorta at the isthmus.

Steering wheel deformity and serious thoracic or abdominal injury among drivers and passengers involved in motor vehicle crashes

STUDY OBJECTIVE

We assess the relationship between steering wheel deformity and serious thoracic or abdominal injury among drivers and front seat passengers involved in motor vehicle crashes, while adjusting for important crash factors.

METHODS

This was a national population-based cohort of adults involved in motor vehicle crashes from 1995 to 2002 and included in the National Automotive Sampling System Crashworthiness Data System database. Participants were front seat occupants aged 16 years or older involved in motor vehicle crashes with collision. Outcome measure was serious thoracic or abdominal injury, defined as an Abbreviated Injury Scale score greater than or equal to 3 in these body regions.

RESULTS

There were 42,860 persons involved in motor vehicle crashes and seated in the driver or front passenger seat whose data were available for analysis. Five hundred fifty-four (1.3%) persons had serious thoracic injuries, and 169 (0.4%) persons had serious abdominal injuries. In multivariable logistic regression models that adjusted for important crash factors and the National Automotive Sampling System Crashworthiness Data System sampling design, increasing steering wheel deformity was associated with serious thoracic injury in drivers (odds ratio [OR] for each 5-cm increase in steering wheel deformity 1.28, 95% confidence interval [CI] 1.04 to 1.59) and front seat passengers (OR 1.77, 95% CI 1.26 to 2.49). Increasing steering wheel deformity was associated with serious abdominal injury in front seat passengers (OR 1.45, 95% CI 1.11 to 1.89) but not in drivers (OR 0.95, 95% CI 0.79 to 1.15).

CONCLUSION

Steering wheel deformity is an independent predictor of serious thoracic injury in drivers and front seat passengers and is associated with serious abdominal injury among front seat passengers. For these occupants, the risk of these injuries increases incrementally with increasing steering wheel deformity.

Thoracic aortic injury in motor vehicle crashes: the effect of impact direction, side of body struck, and seat belt use

BACKGROUND

Using in-depth, real-world motor vehicle crash data from the United States and the United Kingdom, we aimed to assess the incidence and risk factors associated with thoracic aorta injuries.

METHODS

De-identified National Automotive Sampling System Crashworthiness Data System (U.S.) and Co-operative Crash Injury Study (U.K.) data formed the basis of this retrospective analysis. Logistic regression was used to assess the level of risk of thoracic aorta injury associated with impact direction, seat belt use and, given the asymmetry of the thoracic cavity, whether being struck toward the left side of the body was associated with increased risk in side-impact crashes.

RESULTS

A total of 13,436 U.S. and 3,756 U.K. drivers and front seat passengers were analyzed. The incidence of thoracic aorta injury in the U.S. and U.K. samples was 1.5% (n = 197) and 1.9% (n = 70), respectively. The risk was higher for occupants seated on the side closest to the impact than for occupants involved in frontal impact crashes. This was the case irrespective of whether the force was applied toward the left (belted: relative risk [RR], 4.6; 95% confidence interval [CI], 2.9-7.1; p < 0.001) or the right side (belted: RR, 2.6; 95% CI, 1.4-5.1; p < 0.004) of the occupant's body. For occupants involved in side-impact crashes, there was no difference in the risk of thoracic aorta injury whether the impacting force was applied toward the left or toward the right side of the occupant's body. Seat belt use provided a protective benefit such that the risk of thoracic aorta injury among unbelted occupants was three times higher than among belted occupants (RR, 3.0; 95% CI, 2.2-4.3; p < 0.001); however, the benefit varied across impact direction. Thoracic aorta injuries were found to be associated with high impact severity, and being struck by a sports utility vehicle relative to a passenger vehicle (RR, 1.7; 95% CI, 1.2-2.3; p = 0.001).

CONCLUSION

Aortic injuries have been conventionally associated with frontal impacts. However, emergency clinicians should be aware that occupants of side-impact crashes are at greater risk, particularly if the occupant was unbelted and involved in a crash of high impact severity.

Change in Velocity and Energy Dissipation on Impact in Motor Vehicle Crashes as a Function of the Direction of Crash: Key Factors in the Production of Thoracic Aortic Injuries, Their Pattern of Associated Injuries and Patient Survival A Crash Injury Research Engineering Network (CIREN) Study

OBJECTIVE

To examine the effect of change in velocity (MV) and energy dissipation (IE) on impact, above and below the test levels for federal motor vehicle crash (MVC) safety standards, on the incidence of aortic injury (AI) and its mortality and associated injury patterns in frontal (F) and lateral (L) MVCs. Comparison of 80 AI and 796 non-AI patients of AIS=3.

METHODS

Eight hundred seventy-six MVC adult drivers or front-seat passengers (552 F and 324 L) evaluated by 10 Level I CIREN study Trauma Centers together with vehicle and crash scene engineering reconstruction. Patient seatbelt and/or airbag use correlated with clinical or autopsy findings.

RESULTS

In AI, 63% of cases were dead at the scene and only 16% survived to leave hospital. The relation between IE dissipated in the MVC and the DeltaV on impact was exponential as DeltaV increased, but the rise in IE for a given DeltaV was greater in LMVC than in FMVC (p <0.05). A more rapid rise in IE/DeltaV occurred above the mean DeltaV of 48 +/- 19.7 kph (30 mph) in FMVC and above the mean DeltaV of 36 +/- 16.2 kph (23 mph) in LMVC. As DeltaV increased above these means, 65% of 46 FMVC aortic injuries (AIs) and 64% of 34 LMVC AIs occurred. In AI patients there was evidence of focusing of the point of IE impact on the upper chest with a higher incidence of rib1-4 fractures than in non-AI (p <0.01) and more brain, heart, lung and spleen injuries (p <0.01) consequent to lower seatbelt use (p <0.01), but LMVC also had more pelvic fx (p <0.05). Airbags + seatbelts in FMVC and seatbelts in LMVC reduced mortality (p <0.05) Comparison of AI incidence in three successive 4-year vehicle model year periods showed a progressive decrease as new safety devices were introduced (p < 0.05).

CONCLUSIONS

The implications for AI of the focused IE at the upper chest suggest a probable mechanism for MVC AI with the pressurized aortic arch acting as the long arm of a lever system with the fulcrum at the subclavian artery, producing maximum torsional strain at the short arm of the isthmus where 75% of the AIs occurred. AI mortality is also influenced by the associated injuries. To develop more effective safety systems to prevent AI, MVC safety testing with airbags and seatbelts should be carried out at DeltaVs of 1 SD above means for FMVC and LMVC.

Blunt trauma to large vessels: a mathematical study

BACKGROUND

Blunt trauma causes short-term compression of some or all parts of the chest, abdomen or pelvis and changes hemodynamics of the blood. Short-term compression caused by trauma also results in a short-term decrease in the diameter of blood vessels. It has been shown that with a sudden change in the diameter of a tube or in the direction of the flow, the slower-moving fluid near the wall stops or reverses direction, which is known as boundary layer separation (BLS). We hypothesized that a sudden change in the diameter of elastic vessel that results from compression may lead not only to BLS but also to other hemodynamic changes that can damage endothelium.

METHODS

We applied Navier-Stokes, multiphase and boundary layer equations to examine such stress. The method of approximation to solve the BL equations was used. Experiments were conducted in an aerodynamic tube, where incident flow velocity and weight of carriage with particles before and after blowing were measured.

RESULTS

We found that sudden compression resulting from trauma leads to (1) BLS on the curved surface of the vessel wall; (2) transfer of laminar boundary layer into turbulent boundary layer. Damage to the endothelium can occur if compression is at least 25% and velocity is greater than 2.4 m/s or if compression is at least 10% and velocity is greater than 2.9 m/s.

CONCLUSION

Our research may point up new ways of reducing the damage from blunt trauma to large vessels. It has the potential for improvement of safety features of motor vehicles. This work will better our understanding of the precise mechanics and critical variables involved in diagnosis and prevention of blunt trauma to large vessels.

Endovascular treatment of traumatic thoracic aortic rupture combined with diaphragmatic rupture--a case report

The purposes of this report are to describe the immediate repair of a diaphragmatic rupture and subsequent endovascular treatment of a thoracic aortic rupture secondary to blunt chest and abdominal trauma and to discuss the outcome in the light of the trauma scores. A 29-year-old man was injured in a car collision. There were signs of a left diaphragmatic rupture and spleen injury. After urgent laparotomy, the diaphragm was repaired. The spleen appeared uninjured; however, there was a dissection with a transmural tear of the thoracic aorta, which was subsequently treated intraluminally by using a Talent endovascular graft and two AneuRx aortic extension cuffs. The patient fully recovered, and the thoracic endograft showed no evidence of endoleak both 1 month and 1 year after treatment. Fourteen months after the operation, the patient is doing well. Endoluminal techniques can be used successfully in the immediate repair of thoracic aortic injuries, even in the presence of a diaphragmatic rupture. With the introduction of advanced repair modalities, such as endovascular techniques, mortality rates will decrease and may eventually alter injury-scoring systems such as the Injury Severity Score.

Occupant- and collision-related risk factors for blunt thoracic aorta injury

BACKGROUND

Blunt thoracic aortic injury (BAI) is a rare and highly lethal injury. We sought to identify occupant and collision characteristics associated with motor vehicle collision (MVC)-related BAI.

METHODS

The 1995 to 2000 National Automotive Sampling System data files were used. The National Automotive Sampling System is a national probability sample of passenger vehicles involved in police-reported tow-away MVCs. The risk of BAI was calculated according to specific occupant (e.g., age, seat belt use) and collision (e.g., delta-V [estimated change in velocity], vehicular intrusion) characteristics. The association between BAI and these characteristics was calculated using risk ratios (RRs) and associated 95% confidence intervals (CIs).

RESULTS

Specific occupant and collision characteristics demonstrated independent association with BAI. Occupant characteristics included age >or= 60 (RR, 3.6; 95% CI, 2.5-5.2), seat belt use (RR, 0.3; 95% CI, 0.2-0.5), and being a front-seat occupant (RR, 3.1; 95% CI, 1.5-6.3). Frontal and near-side MVCs were associated with an increased risk (RR, 3.1; 95% CI, 1.9-5.1; and RR, 4.3; 95% CI, 2.6-7.2, respectively) relative to other collision types. Collisions with a delta-V >or= 40 km/h (RR, 3.8; 95% CI, 2.6-5.6) or that produce extensive vehicle crush (>or= 40 cm) (RR, 4.1; 95% CI, 2.7-6.3) or intrusion (>or= 15 cm) (RR, 5.0; 95% CI, 3.5-7.3) also increase the risk of BAI.

CONCLUSION

The risk factors for BAI identified in this study support generally accepted etiologic mechanisms for this injury.

Prediction of injuries to the heart and thoracic aorta in unrestrained drivers

The purpose of the study was to investigate factors predicting injuries to the heart and/or thoracic aorta (H/TA) of unrestrained drivers in frontal motor vehicle collisions. We retrospectively analyzed findings of forensic autopsies of 37 unrestrained drivers of automobiles without airbags involved in frontal collisions. Mechanisms of injury, injury severity, presence of major injuries, and the number of fractured ribs were examined in each case. Victims were subdivided for comparison into those with (19 cases) and without (18 cases) H/TA injuries. The injury severity score and the abbreviated injury scale of the chest were significantly higher in persons with H/TA injuries (65.3+/-15.7 and 5.4+/-0.9) than in persons without (31.6+/-22.0 and 1.8+/-1.9). Because univariate analysis showed that the presence of multiple fractured ribs was an important predictor of H/TA injuries, we examined the relation between H/TA injuries and the number of fractured ribs. Copas's nonparametric smooth binary regression model showed that H/TA injuries were more likely in persons with eight or more fractured ribs. The presence of eight or more fractured ribs predicts H/TA injuries in unrestrained drivers.

Analysis of ionic ratios in myocardial tissue and their relation to cardiac damage

The authors evaluated the usefulness of the postmortem biochemical analysis of ionic ratios in different parts of the heart and their relation to cardiac damage caused by chest trauma, as observed by anatomopathologic study. Fifty-nine 59 cases were studied, selected from routine necropsies, and samples were taken from different sites of cardiac tissue. The cause of death was trauma in 40 cases and nontraumatic causes in 19 cases. The object of this study was to analyze the levels of Na+, K+, Ca+2, Mg+2, and Zn+2 in different zones of the heart, and the relationship between intracellular and extracellular ion ratios and the different causes of death and any anatomopathologic alterations observed. The biochemical tests revealed a possible relation between the ionic values and cause of death. Alterations in cell membrane permeability and corresponding modification of the ionic ratios were produced earlier than histologic alterations, which need longer to establish themselves whether or not they follow a traumatic process.

Incidence and characteristics of motor vehicle collision-related blunt thoracic aortic injury according to age

BACKGROUND

Motor vehicle collision-related blunt thoracic aorta injury (BAI) is rare and highly lethal. Vascular disease as related to advancing age potentially subjects older adults to increased risk of BAI; the mechanisms associated with such injuries may be different as compared with younger adults. The goal of the present study is to test this hypothesis using population-based data.

METHODS

The 1995 to 1999 National Automotive Sampling System data files were used. The National Automotive Sampling System is a national probability sample of passenger vehicles involved in police-reported tow-away crashes. BAI was defined according to the Abbreviated Injury Scale codes. Among those with BAI, information on occupant (age, seating position, restraint use), collision (collision type, delta-V, vehicle intrusion), and outcome characteristics were obtained and compared according to age.

RESULTS

The overall incidence of BAI was 6.8 per 10,000 occupants and there was a steady increase in the BAI rate for advancing decades of life. The proportion of occupants with BAI who die at the scene of the collision is relatively consistent across all age groups ( approximately 85%). Among those who survive to receive medical care, ultimate survival is lowest among those aged 60 and older. Near-side collisions were responsible for more BAI among older adults than other age groups (50% vs. 20.6%, p < or = 0.05). Older adults sustained BAI in collisions with lower delta-V values compared with younger persons (p < or = 0.05).

CONCLUSION

Older adults have the highest rate of motor vehicle collision-related BAI, and their injuries tend to occur in less severe collisions. A high level of suspicion for BAI among older adults should not be reserved for high-energy collisions only.

Blunt traumatic rupture of the thoracic aorta: a report of an unusual mechanism of injury

Classic teaching suggests that blunt thoracic aortic rupture (BTAR) results from high-speed deceleration injury mechanisms. Our recent experience with a patient who sustained fatal aortic rupture resulting from a low-speed crushing injury emphasizes the importance of maintaining a high index of suspicion for BTAR, even in patients with "low-risk" injury mechanisms. Several potential pathophysiologic mechanisms of BTAR are discussed.