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Emergency Ultrasound

Tips & Tricks: Sternal Fractures Diagnosed by POCUS

Sternal fractures can result from significant blunt thoracic trauma, most commonly motor vehicle accidents.1 It used to be a rare diagnosis, but its prevalence is on the rise with increase in traffic and seat belt legislation.2 While isolated sternal fractures is considered a benign injury treated conservatively, morbidity and mortality can result from associated injuries including aortic disruption, pulmonary contusion, myocardial contusion and laceration, pericardial effusion, rib fractures, flail chest, and bone marrow embolization.3,4 Furthermore, sternal fractures can lead to long term sequelae including pseudoarthroses and overlap deformities that may require surgical intervention.5

Chest radiograph is considered the imaging modality of choice for sternal fractures.1,2,6-11 However, it has low sensitivity and specificity, especially when there is minimal displacement. Moreover, it can be difficult to obtain a lateral view in trauma or critically ill patients, which delays the diagnosis and thus further reduces its utility.1,6,8,11 CT has better results but it comes with the extra radiation, cost, time, and personnel.

Literature has demonstrated that ultrasound can be obtained rapidly at bedside with improved performance compared to plain radiographs. German studies suggested that sternal fractures were diagnosed “free of doubts” in all cases, and an examiner was able to locate the injury in less than a minute.7,9 Both Hendrich et al. and Engin et al. found that sonography was able to spot sternal fractures that eluded conventional radiography.2,6 More recent studies illustrated that sonograms can detect sternal fractures 2.5 times better than plain films.8,10 This significantly enhanced sensitivity was evident in the meta-analysis by Yousefifard et al., which indicated that ultrasound has a sensitivity of 91%.12 In our emergency room setting, You et al. showed that sonograms reached an impressive 100% sensitivity and specificity for identifying sternal fracture, compared to a mere 70.8% and 75% for radiography, respectively.11

In addition, ultrasound goes beyond diagnosis; it can assist with therapy once an injury is confirmed. Butt et al. and Wilson et al. delivered accurate and effective hematoma block under sonographic guidance.13,14 To make the treatment more target-specific, Thomas et al. employed parasternal nerve block which led to a 0/10 pain score even on sternal pressure.15 Ultrasound assistance provides direct visualization, which has the advantages of avoiding systemic narcotics use with its toxicity, reducing the amount of anesthetic injected, and preventing complications such as pneumothorax or pericardium puncture. 

These complications arise from the close juxtaposition of sternum with important structures including the heart, lungs, trachea, great vessels, ribs, and clavicles. The sternum consists of three parts: manubrium, sternal body, and xiphoid process, from cephalad to caudal. Sonographically, the sternum’s appearance is similar to other calcified bones – echogenic with posterior acoustic shadowing, relatively superficial, and parallel to the skin (Video 1). Some people have subtle transverse sternal ridges at levels of costal cartilage facets. A fracture manifests as a disruption or step off in the echogenic cortex (Figure 1 and Figure 2, Video 2 and Video 3). For higher grade fractures, ultrasound can reveal independent movement of the two fracture components on either side with respiration.1

 Fig1 tips Fig2 tips

Here are some tips for sternal fracture ultrasound:

·    The patient should be in the supine position (Figure 3).

 Fig3 tips

·    Use a high frequency linear probe. Choose the musculoskeletal, superficial, or small parts exam setting.

·    Place the probe longitudinally – parallel to the long axis of the sternum (Figure 3).

·    Start scanning at the point of maximal tenderness as this often correspond to the fracture site.

·    Apply minimal pressure on the sternum while scanning to prevent discomfort.

·    Know your anatomy - do no mistake the sternomanubrial angle or xiphisternal junction as fractures (Figure 4 and Figure 5, Video 4 and Video 5).

 Fig8 tips Fig5 tips

·    In children and young adults, there may be incomplete sternal fusion at the insertion of costal cartilage. To differentiate between the cartilage and fracture, follow the transverse ridges on the sternal body laterally to see if the cartilage starts at the same level.

·    An anechoic hematoma in situ can help distinguish fracture from normal anatomical structures.

·    Scanning during respiration can facilitate detection of nondisplaced fractures.

 Ultrasound is an excellent image modality for sternal fractures. Not only does it diagnose the pathology quickly, easily, cheaply, and accurately, it also enhances acute pain management by guiding hematoma and nerve blocks. Therefore, it improves patient care with expedited evaluation and efficient treatment. Next time a patient presents with anterior midline chest wall pain from trauma, consider extending your EFAST even more by scanning the sternum!

 

References:

1.     Nickson C, Rippey J. Ultrasonography of sternal fractures. Australas J Ultrasound Med. 2011;14(4):6-11.

2.     Hendrich C, Finkewitz U, Berner W. Diagnostic value of ultrasonography and conventional radiography for the assessment of sternal fractures. Injury. 1995;26(9):601-4.

3.     Lee WJ, Lin HY. Severe chest pain after blunt chest trauma. Emerg Med J. 2011;28(5):451-2.

4.     Recinos G, Inaba K, Dubose J, et al. Epidemiology of sternal fractures. Am Surg. 2009;75(5):401-4.

5.     Johnson I, Branfoot T. Sternal fracture--a modern review. Arch Emerg Med. 1993;10(1):24-8.

6.     Engin G, Yekeler E, Güloğlu R, Acunaş B, Acunaş G. US versus conventional radiography in the diagnosis of sternal fractures. Acta Radiol. 2000;41(3):296-9.

7.     Fenkl R, Von garrel T, Knaepler H. [Emergency diagnosis of sternum fracture with ultrasound]. Unfallchirurg. 1992;95(8):375-9.

8.     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. 2006;25(10):1263-8.

9.     Mahlfeld A, Franke J, Mahlfeld K. [Ultrasound diagnosis of sternum fractures]. Zentralbl Chir. 2001;126(1):62-4.

10.   Rainer TH, Griffith JF, Lam E, et al. Comparison of thoracic ultrasound, clinical acumen, and radiography in patients with minor chest injury. J Trauma. 2004;56(6):1211-3.

11.   You JS, Chung YE, Kim D, et al. Role of sonography in the emergency room to diagnose sternal fractures. J Clin Ultrasound. 2010;38(3):135-7.

12.   Yousefifard M, Baikpour M, Ghelichkhani P, et al. Comparison of Ultrasonography and Radiography in Detection of Thoracic Bone Fractures; a Systematic Review and Meta-Analysis. Emerg (Tehran). 2016;4(2):55-64.

13.   Butt AJ, Sharafeldin K, Masterson E, et al. Sternal fracture: the use of ultrasound in diagnosis and acute pain management. Injury Extra 2007;38:442–4.

14.   Wilson SR, Price DD, Penner E. Pain control for sternal fracture using an ultrasound-guided hemTatoma block. J Emerg Med. 2010;38(3):359-61.

15.   Thomas KP, Sainudeen S, Jose S, et al. Ultrasound-Guided Parasternal Block Allows Optimal Pain Relief and Ventilation Improvement After a Sternal Fracture. Pain Ther. 2016;5(1):115-22.

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