Trauma

Thorax injuries vary considerably from simple, uncomplicated rib fractures to large complicated injuries affecting the chest, combined with injuries in the head, abdomen and extremities. The cause of injury is most often a deceleration trauma, with blunt violence to the chest. In such cases, there is often a combination of injuries to the chest wall, pleura, lungs, and mediastinum.

When a patient with multiple injuries is examined, a lateral view of the cervical column, a frontal chest radiograph, and a frontal view of the pelvis is usually obtained. The frontal radiograph of the lungs must be obtained sitting if the patient's condition permits, otherwise lying. At this stage the primary concern is to detect life-threatening conditions such as tension pneumothorax, haemothorax, mediastinal bleeding, and rupture of the diaphragm. In recent years, it has become increasingly frequent to use CT scans early in the examination of severely multitraumatized patients. Thus, one and the same examination provides more complete details of injuries in different organs, together with the possibility of making a more precise diagnosis of the extent of the chest injury. For example, a small anterior pneumothorax is far easier to diagnose by CT scan than by a frontal view of the lungs. This also applies to bleeding in the lung and pleural cavity, and, above all, to mediastinal injuries, the most important of which is aortic rupture.

Chest wall injuries

Fractured ribs are the most common finding in trauma of the thorax. Fractures of the 5th - 9th ribs are most often seen. Fractures of the 1st, and to some extent the 2nd rib, do not usually occur as isolated findings, but are seen in combination with other injuries to the thorax, for example fracture of the clavicle. Fractures of the 1st and 2nd ribs necessitate considerable blunt violence, and are usually accompanied by injuries to vessels and nerves, together with mediastinal injuries such as

Figure 86. Fracture of sternum through the upper part of the body of the sternum with forward and cranial dislocation of the distal fragment (arrows).

Figure 87. Fracture of sternum with large retrosternal haematoma. Considerable widening of the mediastinum in PA chest x-ray.

Figure 88. Fracture of sternum with large retrosternal haematoma - CT scan.

rupture of vessels and the trachea. Fractures of the lowest ribs are often accompanied by simultaneous injuries of the liver and spleen (rupture).

Fractured ribs may be seen together with pneumothorax, indicating a penetrating pleural injury. Multiple fractured ribs may cause pulmonary collapse involving larger or smaller parts of a lung, and accompanied by unstable respiration (flail chest).

Fracture of the sternum is frequently seen with severe injuries to the thorax (Fig. 86), usually with dislocation of the different fragments in relation to each other. A retrosternal hematoma of varying size often develops. This will be visible as a widening of the mediastinum (Fig. 87). A CT scan is necessary (Fig. 88) in order to assess the extent of the hematoma and to verify the diagnosis, making certain that it is not caused

by another simultaneous large mediastinal injury such as rupture of the aorta. Cardiac injury, such as myocardial contusion or traumatic ventricular septal defect, should be considered in patients with sternal fracture.

Pleural injuries

Pleural injuries are due to complications arising from rib fractures and other penetrating injuries. The most common complications are pneumothorax (Fig. 89), and hemothorax. A chest radiograph aimed at diagnosing pneumothorax should be taken in the expiratory phase.

Tension pneumothorax may arise after penetrating injuries. Positive pressure arises in the punctured pleural cavity, with displacement of the heart and mediastinal structures over towards the contralateral side. This may compromise venous return to the heart and reduce filling pressure in the right ventricle. This is a life-threatening condition needing immediate relief, e.g. drainage of the affected pleural cavity.

Bleeding into the pleural cavity is usually caused by severance of veins, and is most often seen at the same time as pneumothorax (hemopneumothorax). If fat is present in the pleural fluid, it is a sign of chylothorax and is due to rupture of lymph vessels. Rupture of the thoracic duct may occur with blunt trauma.

Lung injuries

Lung injuries, usually contusion of lung tissue, may be accompanied by injuries of the ribs and pleura (Fig. 90), but are seen just as often without simultaneous rib fractures (Fig. 91). With a compression injury of the lungs, extravasation of blood into the alveoli occurs followed by

development of a secondary transudate. Contusion injuries may cause hypoxia. Bleeding into the lung parenchyma is often seen with contusions. The localization of the bleeding may be both interstitial and intra-alveolar. The radiological changes after contusion resolve rapidly, and after pulmonary contusion the lungs usually return to normal in the course of 5-10 days. However, it may take months before the opacities caused by a haematoma disappear. After a severe lung injury, ARDS (adult respiratory distress syndrome) frequently occurs.

Mediastinal injuries

The most frequent injuries of the mediastinum are aortic rupture, esophageal rupture, tracheal/bronchial rupture, pneumomediastinum, pneumopericardium, and diffuse mediastinal bleeding.

Aortic rupture is one of the most important causes of death after traffic accidents with thorax injuries. The sites of predilection in the aorta are the ascending aorta immediately before the origin of the innominate artery, and the descending thoracic aorta immediately after the origin of the left subclavian artery (70%). If the rupture is situated in the ascending part of the aorta, it is frequently accompanied by cardiac tamponade. Most of these patients die before hospitalization. Of the patients who survive the initial injury, 30% die in the course of the first four hours.

Chest radiography sitting in bed is an important examination in patients with thorax injuries. If the width of the mediastinum is increased in a sitting chest radiograph, or increase in width occurs during the course of the first hours after admission to hospital, aortic rupture is strongly indicated, and angiography should be done emergently (Fig. 92 a, b). A collection of blood over the apex of the left lung (pleural cap) also points strongly towards aortic rupture. It is extremely important to rapidly

establish this diagnosis, and up to 90% normal findings are accepted on aortography in order to disclose 10% of patients with aortic rupture. However, widening of the mediastinum may also occur with diffuse mediastinal bleeding caused by severance of veins. Aortography should always be performed by puncture of the femoral artery, with advancement of a catheter into the ascending aorta immediately above the aortic valves. A right posterior oblique serial radiography is the best projection for making a diagnosis of aortic rupture, although frontal and lateral views may sometimes be necessary in order to demonstrate extravasation of contrast from the aortic lumen (Fig. 93 a, b).

Computed tomography may also provide the diagnosis. The examination shows that a rupture
exists, but the site of the rupture may be difficult to demonstrate with CT, which makes angiography a better choice as the first examination with suspected aortic rupture.

Rupture of the esophagus, trachea and/or bronchial tree may be seen with severe injuries of the thorax, but may be obscured by other, more dramatic injuries. Injuries of this type usually give changes on the chest film in the course of the first 24 hours. The most common findings are pneumomediastinum (Fig. 94), pneumothorax, subcutaneous emphysema and pleural fluid. The diagnosis is made by having the patient swallow water-soluble contrast, thus demonstrating the leakage from the esophagus. If rupture is suspected, contrast media containing barium sulphate must be avoided. One of the two main bronchi usually rupture when there is tracheal/bronchial rupture. The diagnosis is most easily made by bronchoscopy, thus determining localization and extent of the injury.

Diaphragm injuries

Rupture of the diaphragm is encountered usually as a complication of blunt trauma to the thorax. The left diaphragm ruptures more often than the right (Fig. 95). The injury to the diaphragm will often be obscured by the accompanying chest injuries, and not infrequently remains undiagnosed in the period immediately after the injury. If it continues to be undiagnosed and untreated, hernias develop through which parts of the abdominal organs enter the thoracic cavity. If intestine herniates into the chest cavity, strangulation may occur. As injuries to the diaphragm are often accompanied by an elevated diaphragm, rupture of the diaphragm may be difficult to detect, especially in the initial phase when the patient's condition makes it difficult to obtain a frontal film in the standing

position. Computed tomography of the thorax will usually provide the diagnosis (Fig. 96)

Alf Kolbenstvedt, Arnulf Skjennald and Charles B. Higgins