Imaging: Thoracic Trauma Tony Tiemesmann Diagnostic Radiology Bloemfontein Hospital Complex

Heart, Great Vessels, Esophagus, Tracheobronchial Tree, & Lungs Introduction Vital Structures Heart, Great Vessels, Esophagus, Tracheobronchial Tree, & Lungs 25% of MVC deaths are due to thoracic trauma 12,000 annually in US Abdominal injuries are common with chest trauma. Prevention Focus Gun Control Legislation Improved motor vehicle restraint systems Passive Restraint Systems Airbags

Thoracic Skeleton Anatomy 1 12 Pair of C-shaped ribs Sternum Manubrium Ribs 1-7: Join at sternum with cartilage end-points Ribs 8-10: Join sternum with combined cartilage at 7th rib Ribs 11-12: No anterior attachment Sternum Manubrium Joins to clavicle and 1st rib Jugular Notch Body Sternal angle (Angle of Louis) Junction of the manubrium with the sternal body Attachment of 2nd rib Xiphoid process Distal portion of sternum

Anatomy 2 3 weeks of gestation in humans

Anatomy 3 Neural crest Step 1: Neural groove forms.

Anatomy 4 Mediastinum Central space within thoracic cavity Boundaries Lateral: Mediastinal pleura Inferior: Diaphragm Superior: Thoracic inlet Posterior: Thoracic spine Anterior: Sternum & costal cartilages Superior & Inferior mediastinum Inferior mediastinum Anterior Middle Posterior

Anatomy 5 Structures (superior) Structures (inferior) Great Vessels Oesophagus Trachea Nerves Vagus Phrenic Thoracic Duct Structures (inferior) Anterior – fat, lymph nodes Middle – heart, aorta, lower SVC, Trachea & main bronchi, lymph nodes, pulmonary veins & arteries, phrenic nerve Posterior – Aorta, oesophagus, azygous & hemiazygous, thoracic duct, vagus

Heart Heart General Structure Pericardium Epicardium Myocardium Surrounds heart Visceral Parietal Serous 35-50 ml fluid Epicardium Outer Layer Myocardium Muscular layer Endocardium Innermost layer 4 weeks 6 weeks

Great Vessels Great Vessels Aorta Superior Vena Cava Fixed at three sites Annulus Attaches to heart Ligamentum Arteriosum Near bifurcation of pulmonary artery Aortic hiatus Passes through diaphragm Superior Vena Cava Inferior Vena Cava Pulmonary Arteries Pulmonary Veins

Oesophagus Esophagus Enters at thoracic inlet Posterior to trachea Exits at esophageal hiatus

Pathophysiology Blunt & Penetrating Trauma Results from kinetic energy forces Subdivision Mechanisms Blast Pressure wave causes tissue disruption Tear blood vessels & disrupt alveolar tissue Disruption of tracheobronchial tree Traumatic diaphragm rupture Crush (Compression) Body is compressed between an object and a hard surface Direct injury of chest wall and internal structures Deceleration Body in motion strikes a fixed object Blunt trauma to chest wall Internal structures continue in motion Age Factors Pediatric Thorax: More cartilage = Absorbs forces Geriatric Thorax: Calcification & osteoporosis = More fractures

Cardiovascular 1 Myocardial Contusion Occurs in 76% of patients with severe blunt chest trauma Right Atrium and Ventricle is commonly injured Injury may reduce strength of cardiac contractions Reduced cardiac output Electrical Disturbances due to irritability of damaged myocardial cells

Pericardial Tamponade Cardiovascular 2 Pericardial Tamponade Restriction to cardiac filling caused by blood or other fluid within the pericardium Occurs in <2% of all serious chest trauma However, very high mortality Results from tear in the coronary artery or penetration of myocardium Blood seeps into pericardium and is unable to escape 200-300 ml of blood can restrict effectiveness of cardiac contractions Removing as little as 20 ml can provide relief

Myocardial Aneurysm or Rupture Cardiovascular 3 Myocardial Aneurysm or Rupture Occurs almost exclusively with extreme blunt thoracic trauma Secondary due to necrosis resulting from MI Signs & Symptoms Severe rib or sternal fracture Possible signs and symptoms of cardiac tamponade If affects valves only Signs & symptoms of right or left heart failure Absence of vital signs

Traumatic Aneurysm or Aortic Rupture Cardiovascular 4 Traumatic Aneurysm or Aortic Rupture Aorta most commonly injured in severe blunt or penetrating trauma 85-95% mortality Typically patients will survive the initial injury insult 30% mortality in 6 hrs 50% mortality in 24 hrs 70% mortality in 1 week Injury may be confined to areas of aorta attachment Signs & Symptoms Rapid and deterioration of vitals Pulse deficit between right and left upper or lower extremities

Other Vascular Injuries Cardiovascular 5 Other Vascular Injuries Rupture or laceration Superior Vena Cava Inferior Vena Cava General Thoracic Vasculature Blood Localizing in Mediastinum Compression of: Great vessels Myocardium Esophagus

Traumatic Esophageal Rupture Oesophagus Traumatic Esophageal Rupture Rare complication of blunt thoracic trauma 30% mortality Contents in esophagus/stomach may move into mediastinum Serious Infection occurs Chemical irritation Damage to mediastinal structures Air enters mediastinum Subcutaneous emphysema and penetrating trauma present

Imaging: Radiography NB NB Delay only in life-threatening conditions Haemo/Pneumothorax Fractures (ribs - flail chest) Mediastinum – widened, air Diaphragmatic rupture Foreign bodies

Imaging: Computed tomography Blunt lung trauma – blood in bronchi, interstitial blood Cardiac & major vessel trauma (with or without angio) critical area to evaluate on CT scans is the aorta at the level of the left main pulmonary artery (90% of all CT-detected aortic injuries begin at or just above this level and that 85% of aortic injuries end at or just below it) CTA Bony elements & surrounding tissue

Imaging: MRI Stable patients CT unequivocal NB: vascular and spinal injuries

Imaging: Ultrasound Quick & non-invasive FAST (focussed assessment for sonographic evaluation of the trauma patient) Percardiac – percardiocentesis Sternum Pleural Pulmonary contusion Diaphragm NB: Degree of confidence

Imaging: Echocardiography Acute blunt cardiac injury – chamber disruption, valvular incompetence, coronary artery thrombosis, ventricular aneurysm formation, myocardial contusion Detectable functional changes – cardiac function, motion abnormalities of the cardiac wall, pericardial effusions, valvular injury

Imaging: Angiography Widened mediastinum on CXR (3% aortic injury) Aortogram – rupture/pseudoaneurysm

Imaging: Nuclear medicine Continuing symptoms with no radiological signs Skeletal - technetium-99m diphosphonate Cardiac - thallium-201 chloride

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References Kaewlai R, Avery L, Asrani A, Novelline R. Multidetector CT of Blunt Thoracic Trauma. RadioGraphics 2008; 28:1555–1570. Jin W, Yang DM, Kim HC, Ryu KN. Diagnostic values of sonography for assessment of sternal fractures compared with conventional radiography and bone scans. J Ultrasound Med. Oct 2006;25(10):1263-8; quiz 1269-70. Gavelli G, Canini R, Bertaccini P. Traumatic injuries: imaging of thoracic injuries. Eur Radiol. Jun 2002;12(6):1273-94. Khan AL et al. Trauma thoracic imaging. Medscape Oct 2011. DiMaio VJM, Dana SE. Handbook of forensic pathology 2nd ed. CRC Press. 2006.