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Nonpenetrating Injuries to the Thoracic Aorta

1969; Radiological Society of North America; Volume: 92; Issue: 3 Linguagem: Inglês

10.1148/92.3.541

1527-1315

Timothy T. Flaherty, Gene P. Wegner, Andrew B. Crummy, William P. Francyk, Florencio A. Hipona,

Hip and Femur Fractures

THIS YEAR over 50,000 persons in the United States will die as a result of automobile accidents. Autopsy examination shows that 1 in 6 sustain fracture of the thoracic aorta (4). Immediate exsanguination occurs in most, but 10 to 20 per cent of the injured will survive long enough for reparative surgery provided the diagnosis is established (8, 12, 16). Correlation of radiologic with clinical evidence allows the diagnosis to be made with confidence. I t is our purpose to review the findings in 12 cases of aortic fracture, 10 of which were seen in the acute phase. Pathogenesis Nonpenetrating injuries of the thoracic aorta may be produced by direct forces such as compression or blast or by indirect forces such as deceleration, or by a combination of these. The forces generated by rapid deceleration in either the vertical or horizontal plane are the most common causes of aortic fracture (8, 12, 16). Haas (5) studied patients who died in airplane accidents and showed that vertical forces of deceleration produce aortic fracture just above the aortic valve. In contrast, horizontal deceleration, the type usually seen in automobile accidents, characteristically produces aortic fracture just distal to the left subclavian artery at the site of the insertion of the ligamentum arteriosum (1, 4, 8, 12). The majority of aortic fractures occur at this site, a fact which is a reflection of the preponderance of automobile victims. The aortic fracture is caused by the shearing force generated by differences in inertia between the mobile and the relatively immobile segments of the vessel (1, 7, 9, 13, 19). Cammack (1) concluded that the tear begins in the intima and proceeds outward and may vary from only intimal disruption to a fracture of all layers of the aortic wall (8). Typically, the fracture is transverse and may be circumferential. If the disruption is circumferential, the involved layers may retract (Fig. 1). In some patients the adventitia, which has been estimated to provide 60 per cent of the tensile strength of the aorta (2), may remain intact and prevent immediate exsanguination. Early survival in others is dependent upon the formation of a mediastinal hematoma which .tamponades the rupture. In reported series (8, 16) 80 per cent of the patients with aortic rupture at the isthmus were dead on arrival at the hospital. Parmley (8) reviewed 125 cases of fracture of the aortic isthmus. In 24 of these the patient survived the initial incident, and 25 per cent of these survivors were dead in twenty-four hours. Sixtyseven per cent were dead within four weeks if untreated. Six of his untreated patients (25 per cent) survived the first month. One died at the seventy-sixth, one at the one hundred twentieth, and one at the three hundredth day while 3 others died between the second and fourth years. There were 2 survivors and they underwent surgical correction at three and eighteen months.