Stephen Ramaley, MD
Sternal fractures and Evidence of Blunt Cardiac Trauma
Image courtesy of google images: medicine.medscape.com
A 44-year-old male presents to the ER after an MVC. The patient was a restrained driver, stopped at a stoplight when he was rear-ended by another vehicle traveling at 25 m.p.h. There was no airbag deployment. He is talking on presentation, complaining of chest pain and shortness of breath. He has bilateral breath sounds. Vitals were notable for tachycardia at 100 BPM and tachypnea at 22 breaths per minute. On examination there is an obvious seatbelt sign across his chest and he is exquisitely tender to palpation over the sternal area. There is no crepitus or noticeable displacement of the sternum. There were no other injuries seen on exam. A chest x-ray, 12-lead EKG,and e-FAST exam were normal. His vitals normalized with morphine administration. Labs were normal including troponin. During his stay in the ED, he continued to complain of sternal pain. CT scan of the sternum revealed sternal body fracture. He was admitted to telemetry for observation, serial EKGs, and ECHO which were all normal. He was discharged in 2 days to home with a pain control regimen. Two week follow-up in trauma clinic revealed patient’s pain had greatly improved.
Sternal fractures occur in about 3% of cases of blunt anterior chest trauma, usually associated with deceleration injuries. Like the above case, over 60% of sternal fractures are secondary to MVCs2. Sternal fractures are worrisome for their association with blunt cardiac injury, pneumo/hemothorax, pulmonary contusion, rib fractures, flail chest, spinal column injury, aortic and other vasculature injury. Many presentations of blunt cardiac injury (BCI) such as pericardial injury, valvular dysfunction, coronary artery injury and cardiac chamber rupture are evident during or soon after initial evaluation. More occult presentations of BCI, such as cardiac contusion, often leading to dysrhythmia (incidence of about 1.5%3), may not manifest during the initial evaluation. Due to this possible delayed presentation of BCI these patients are often admitted for observation.
The initial management of the suspected sternal fracture patient should begin as any other trauma patient (airway, breathing, circulation, disability and exposure). In regards to possible sternal fractures, patients usually complain of isolated pain to the sternum. The pain is usually worst with chest wall motion, and is easily reproduced on palpation. Crepitation and displacement is usually not evident on examination unless the fracture of the sternum is significantly unstable. The clinician must also assess for associated pathology, as a trauma with enough force to cause a sternal fracture can cause significant injury.
While the role of imaging (discussed below) is important in the workup to assess for associated injuries, the diagnosis of sternal fracture can be made clinically. Primarily, this includes cardiac enzymes and a12- lead EKG to assess for dysrhythmia or ST changes indicating cardiac injury. Multiple studies have shown that an EKG alone is not sufficient to rule out BCI 4,5. One prospective study showed that use of EKG to rule out BCI has a NPV of 95%. When combined with troponin-I, NPV approaches 100%5. These studies incorporated two troponin levels drawn 8 hours apart. A study of patients with blunt chest trauma determined that CK and CK-MB markers are unable to differentiate patients with cardiac injury from those without 6.
There are a few imaging modalities available for the emergency clinician. Lateral plain films remain the diagnostic tool of choice while AP chest views are usually sufficient to detect associated injuries. Single blinded studies comparing plain films to ultrasound have shown that sensitivity for detection of sternal fracture is 70.8% with plain films7. Sternal views can provide a better view of the sternum and can also be useful. Ultrasound in recent research has been shown to be promising in its diagnostic utility. Studies have shown that the sensitivity for the ultrasound detection of sternal fractures approaches 100%4. Sternal fracture on ultrasound is evidenced by the discontinuity of the bony cortex. Ultrasound also has the benefit of being able to assess the pericardium, pleural space and vasculature as well.
The location of the sternal fracture has been shown to have a impact on the outcome. While the most common diagnosed area of sternal fracture is of the body. The manubrium, the broad upper part of the sternum with a quadrangular shape, has a higher incidence of BCI as well as other related injuries. A recent retrospective study showed that patients with fractures of the manubrium have worse outcomes (23.8% died) and are admitted to the ICU more frequently (76.2%) 9. These findings were due to the increase in associated injuries. Specifically, they found with manubrium fractures, rib and thoracic spinal fractures were much more common.
Since there has been various practice and controversy on exactly how to manage sternal fractures the Eastern Association for Surgery of Trauma revised their guidelines. In 2012, now a level 2 recommendation (moved from level 3), the presence of sternal fracture in the setting of a normal EKG and one normal troponin level does not require further evaluation for BCI. There is no recommendation for a screening echocardiography. The full list of recommendations regarding the screening of blunt cardiac injury can viewed at www.east.org/resources/treatment-guidelines/blunt-cardiac-injury,-screening-for.
In summary, in the emergency department, after the primary and secondary surveys are complete, the workup of sternal fracture (not involving the manubrium) is fairly straight-forward. Initially, the clinician should do a 12-lead ECG looking for any ST changes or dysrhythmias. Trop-I should also be sent. Imaging is optional for the diagnosis of sternal fracture but helpful in ruling out other pathologies. In isolated sternal injuries (not of the manubrium) the patient can be safely discharged after normal ECG and Troponin levels. If a fracture of the manubrium is diagnosed or suspected, the clinician should realize that these patients have poorer outcomes due to associated injuries and should consider further detailed studies.
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