Diagnostics

Emergency bedside ultrasound for the diagnosis of rib fractures

Stewart Siu-Wa Chan MBBS (Syd), FRCSEd, FHKAM (Emergency Medicine)?

Emergency Department, Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China

Received 3 March 2008; revised 22 March 2008; accepted 13 April 2008

Abstract The scope of clinical applications of emergency ultrasonography continues to expand. Bedside ultrasound has been typically described as an “extension of the palpating hand” and a “visual stethoscope” during physical examination. One of the relatively newer applications is its use in the detection of rib fractures. The author discusses the technique, applicability, limitations, and role of emergency ultrasound in the diagnosis of rib fractures.

(C) 2009

Introduction

The use of ultrasound in emergency medicine is rapidly expanding. A growing number of emergency departments (EDs) have now acquired ultrasound scanners. More and more emergency physicians are formally trained to use ultrasound, applying this modality to guide clinical practice. This paper discusses the technique, applicability, limitations, and value of using ED ultrasound in the diagnosis and subsequent management of acute rib fractures.

Sonography has been reported to be useful in the detection of fractures. High-resolution ultrasound is thought to have a unique role especially for fractures that are difficult to detect with Plain radiography, such as fractures of unossified bone in children. Hence, several authors have reported using ultrasound to diagnose elbow and forearm fractures in children and infants [1-3]. Ultrasound has also

* Emergency Department, Prince of Wales Hospital, 30-32 Ngan Shing Street, Shatin, NT, Hong Kong, China. Tel.: +852 2632 2219; fax: +852

2337 3226.

E-mail address: [email protected].

been used to guide reduction of Femoral shaft fractures, thoracolumbar burst fractures, and zygomatic arch fractures [4-6]. Ultrasound avoids the ionizing radiation of fluoro- scopy, and it allows for real-time evaluation of the reduction. Recently, emergency physicians have reported using bedside ultrasound as a reliable and convenient method to guide reduction of forearm fractures in children [7,8].

Accuracy

A MEDLINE search using the terms ultrasound and rib fractures found only 4 studies published in English language indexed literature that investigated the accuracy of ultra- sound in the diagnosis of rib fracture on ED patients. Radiologists performed the ultrasound scanning in all these studies [9-12]. Griffith et al [9] found that ultrasound is more sensitive than chest radiography (78% against 12%) in detecting rib fractures in a prospective study of 50 patients with clinical suspicion of rib fracture. In another prospective observational study, Kara et al [10] reported that ultrasound revealed rib fractures in approximately 40% of 37 patients with minor blunt chest trauma and initially undetected rib

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fractures on chest radiographs. Furthermore, Rainer et al [11], in a prospective study of 88 patients having isolated mild-to-moderate Blunt chest injury, found that the sensitiv- ities of ultrasound, clinical acumen, and chest radiography were 80.3%, 26.0%, and 23.7%, respectively, for the detection of chest wall fractures. Finally, Hurley et al [12] prospectively assessed a smaller series of 14 patients with clinical suspicion of rib fracture and found that ultrasound was marginally more sensitive than radiography for diagnosing rib fracture. Ultrasound also detects costal cartilage fractures and costochondral junction fractures better than radiography [9,13]. Healing fractures with callous formation may also be detected sonographically [9]. Overall, these studies show that the use of ultrasound greatly improves the sensitivity in detecting rib fractures in ED patients. In addition, ultrasound is also found to be useful in detecting sternal fractures [14].

Applicability

Although the correct identification of rib fractures by ultrasound as opposed to clinical suspicion usually does not alter patient management to a large extent, there are, in fact, a number of important advantages in practice. First, early diagnosis of rib fractures may prompt initiation of an appropriate pain management protocol, such as that which justifies the use of regular parental opiates or Intercostal nerve blocks. An accurate diagnosis is also important to

Fig. 1 Normal sonogram of the anterior chest wall using a 7.5- MHz linear transducer. The double arrows show the short-axis view of a rib, with its hyperechoic margin and posterior acoustic shadowing. P denotes the “pleural line” that is also hyperechoic and that should not be mistaken as the rib margin.

Fig. 2 Long-axis view of a fractured left third rib of a patient using a 12-MHz linear transducer. The disruption of the hyperechoic cortical alignment is shown by the arrows.

guide patient Disposition decisions. Rib fractures have been found to correlate significantly to morbidity and mortality in the elderly population; hence, Prompt diagnosis and precau- tionary measures taken to monitor for complications are essential [15-17]. Admission to hospital is frequently recommended for patients with 3 or more rib fractures. For those with multiple mid-to-lower rib fractures, Abdominal computed tomography scanning may be indicated to rule out hepatic, splenic, and other Intra-abdominal injuries. Further, with a diagnosis of rib fracture, more accurate patient information regarding the estimated time for resolution of pain can be given. This is important in regard to advice for

Fig. 3 Left oblique chest radiograph demonstrating the fracture.

return to work and activities, especially for manual workers and athletes.

Technique

The technique of ultrasound scanning in detecting rib fractures is not complicated and can easily be learned by an emergency physician already trained in the basics of goal- oriented ultrasonography [18]. It involves first identifying the site of maximal tenderness by clinical examination. A high-frequency 7- to 12-MHz linear transducer is used [9-13,18]. The transducer is placed perpendicular to the long axis of the rib to identify the posterior surface of the rib by its distinct acoustic shadowing (Fig. 1). This short-axis view is useful for distinguishing the posterior rib margin from the pleural line (P), both appearing as bright white or hyperechoic lines. The rib demonstrates posterior (dark or anechoic) shadowing because bone reflects a large propor- tion of the ultrasound beam uniformly back toward the transducer. The transducer is then rotated 90 degrees and aligned parallel to the long axis of the rib. The site of maximal tenderness is then assessed to look for discontinuity of cortical alignment, visualized as a break in the hyperechoic rib margin. As a routine, the entire length of the rib is scanned, followed by further assessment of adjacent ribs as indicated from clinical examination. One advantage of ultrasound is that multiple views of different planes can be readily obtained and visualized in real time.

Fig. 2 shows the scan of a 78-year-old woman who presented to the ED with left upper lateral chest wall pain after a fall. A posteroanterior chest radiograph did not detect any fracture. In this long-axis sonographic view of the third rib, a break in the cortical continuity is revealed, identifying the fracture. The scan was performed by one of several emergency physicians credentialed to perform ultrasound in the author’s department. This was also the physician who initially saw the patient. In this case, the fracture was also demonstrated by chest radiography in an oblique rib view (Fig. 3). Other reported but less common sonographic signs suggestive of fracture are the following: (a) a linear acoustic edge shadow posterior to the fracture, (b) a reverberation artifact posterior to the fracture, and (c) the presence of a hypoechoic hematoma [9,10,12,18]. Once a rib fracture is diagnosed, ultrasound can then be used conveniently and reliably to exclude the likely complications of pneumothorax and hemothorax [19,20].

Limitations

There are 2 specific limitations. First, the ultrasound protocol may be time consuming. In their studies, Hurley et al

[12] reported an average time of 13 minutes, whereas Griffith et al [9] also reported that each ultrasound examination

required 10 to 15 minutes. Nevertheless, these scans were performed by radiologists in radiology departments. It may be more feasible if the scans are performed by emergency physicians in the ED at the time of consultation and physical examination. Modern portable machines and handheld scanners can conveniently provide for such practice. The additional time required would not be very significant when compared with the waiting time for chest radiography in a busy ED. In the author’s experience and opinion, a clinician is likely to be able to complete the ultrasound protocol in less time than that required by a radiologist or an ultrasound technician. However, the relative time constraint does render ultrasound diagnosis of rib fractures less valuable in major trauma cases in which “fast” scans are preferred. A second limitation is that retroscapular ribs and the infraclavicular portion of the first rib are technically inaccessible by sonography. However, these are uncommon sites for rib fractures [9].

In conclusion, bedside ultrasound is a valuable modality for the diagnosis of rib fractures and should be used more frequently in the ED. Although the technique described is not new and is already being used in some academic emergency centers and by radiologists, it is hoped that this report can stimulate its practical use even in smaller EDs and for more emergency physicians to be able to master the skill. There is also a need for more good quality emergency medicine research on this area of focus, including studies of improved patient outcomes, cost-effectiveness, and learning curves. With handheld equipment, the technique may also be applied to clinical areas where radiography is not available, such as out-of-hospital care, wilderness medicine, tactical medicine, and disaster medicine.

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