I.  Introduction and Indications

Acute sternal fractures are a common injury seen following motor vehicle collisions and blunt chest trauma.  About 8-10% of admitted patients with blunt injury to the chest have been found to have sternal fractures. (1,2)  Most commonly these occur secondary to direct chest wall impact, likely from the steering wheel or dashboard of a vehicle involved in collision.  Isolated sternal fractures can be complicated by significant cardiac contusion and arrhythmia. (3)  Ultrasound is a useful tool in evaluating for sternal fracture, which can easily be missed on standard anteroposterior chest radiography.  In addition, lateral radiography can be difficult to obtain in many of these patients.  In one study ultrasound was found to be 100% sensitive and specific in the diagnosis of acute sternal fracture. (4)
Ultrasound also can be utilized to evaluate the sternoclavicular joint.  This is an atypical joint with articulating surfaces covered with fibrocartilage.  The capsule thickens anteriorly and posteriorly to form the sternoclavicular ligaments.  Sonography can be useful in visualizing dislocation/disruption at this joint.

II.  Anatomy

The sternum is a flattened bone with a smooth surface, which forms the middle portion of the anterior chest wall.  It is comprised of the manubrium superiorly, the body, and the xiphoid process inferiorly (Illustration 1).  The superior border of the sternum presents the center to the jugular notch, the junction of the manubrium with the body forms the sternal angle. The sternum articulates on either side with the medial end of the clavicle and upper seven costal cartilages.

Illustration 1:  Anatomy and spatial relation of the sternum.

III.  Scanning Technique, Normal Findings and Common Variants

A high frequency, linear array transducer should be used to evaluate the superficial sternum.  This will allow for maximal resolution and the flat transducer surface also provides an optimum conduction interface with the chest wall.  The patient should be positioned supine, and the sternum should be scanned in its entirety (manubrium, body, xiphoid) in both longitudinal (Figure 1and video 1) and transverse (Figure 2) planes.

Figure 1:  Longitudinal view of sternum. The hyperechoic line marks the periost of the sternum (yellow), the red arrow indicates the sternal angle (Courtesy of B.Hoffmann, M.D.).

Video 1: The probe is placed over the sternal angle in longitudinal orientation
and slowly moved caudal towards the xiphoid (Courtesy of B.Hoffmann, M.D.).

Figure 2:  Transverse view of mid-sternum (yellow),
the pleural line is maked with red (Courtesy of B.Hoffmann, M.D.).

There are several variants that can mimick sternal fracture (1).  This includes (in order of incidence):

            - Sternal foramen - 4.5%; typically round in the lower 3rd of the sternum
            - Suprasternal bone - 4.1%; can be single or paired
            - Sternoxiphoid pseudoforamen - 3.6%
            - Sternal cleft - 0.8%
            - Manubrial cleft - 0.6%

IV.  Pathology

In a case of suspected sternal fracture, particular attention should be paid to the area of maximal tenderness.  The presence of fracture will be illustrated by any cortical discontinuity, disruption, or step-off (Figure 3).  The detection of localized hematoma or fluid will also aid in the localization of fracture.  In addition to fracture detection, the emergency physician can perform ultrasound-guided hematoma block for pain control. (5)

Figure 3 and Video 2: Example of sternal fracture.

Figure 4 and Video 3: Example of sternal fracture.

Figure 5 and Video 4: Example of sternal fracture (Courtesy of B.Hoffmann, M.D.)

Figure 6 and Video 5: Example of sternal fracture.

 

V.  Pearls and Pitfalls

• Mistaking sternal variants (listed above) for fracture

• Failure to scan the sternum in its entirety

• Failure to rotate the transducer ninety degrees and isolate a fracture in 2 planes

• Interpreting manubrosternal/sternoxiphoid junctions as a fracture

• Failure to realize difficulty in determining magnitude of displacement with ultrasound (can be difficult to visualize lateral/posterior aspects)

• Scanning the patient during in- and expiration can increase the accuracy of detecting non-displaced sternal fractures (Video 4)

 

VI.  References

1. 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.

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. Wiener Y, Achildiev B, Karni T, Halevi A.
Echocardiogram in sternal fracture. Am J Emerg Med. 2001;19(5):403-5.

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

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