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Pearls & pitfalls for Musculoskeletal Ultrasound
1. DO YOUR HOMEWORK: More and more practitioners are using bedside ultrasound to obtain valuable data that can be used to enhance and expedite patient care. It is important to recognize the limitations of bedside ultrasonography and to stay current with the recent literature. Update your skills regularly and continue to challenge yourself by reading, scanning, and attending advanced courses.
2. AUGMENT CARE: Although ultrasound is not the first-line imaging modality used to detect acute bone fractures, in situations where X-ray is not readily available, bedside ultrasound can be used to provide useful information that can help augment patient care.
3. HIGH FREQUENCY: Most musculoskeletal applications are best performed using a high frequency linear array transducer (13-5 MHz). Remember that high frequency probes allow better visualization of superficial structures.
4. CREATING THE IDEAL SURFACE: Apply a copious amount of gel over the target surface to be scanned. To improve your acoustic window over superficial structures, use water immersion or create an acoustic standoff pad (this can be done with a 500ml bag of saline with gel on both interfaces or a water-filled glove sandwiched between two layers of gel).
5. ASSOCIATED UNDERLYING FRACTURES: An acute hemarthrosis will appear anechoic (black). As clot begins to form within the effusion, it will become more hyperechoic and heterogeneous in appearance. Whenever a traumatic effusion is visualized, always search for an associated underlying fracture.
6. BONES: Bones will appear bright white (hyperechoic) on ultrasound. An acoustic shadow will be noted farfield to the bony cortex.
7. ASSESSING FOR ACUTE FRACTURE: To assess for an acute fracture, scan along the hyperechoic cortical line in search of any break in the cortex. If a cortical irregularity is noted, correlate your sonographic findings with the physical exam. Note that large nutrient vessels can also appear as hypoechoic cortical irregularities on ultrasound. Pressure with the probe or palpation over the noted irregularity should cause pain if the irregularity noted is secondary to an acute fracture.
8. EVALUATING THE CORTEX: To fully evaluate the cortex, scan along the target bone systematically in multiple planes. If you are unsure of findings, use the opposite side for a comparison view.
9. BEDSIDE ULTRASOUND AND PEDIATRICS: Ultrasound diagnosis of fractures has been studied in all long bones and also many of the wrist bones, ankle bones, ribs, and cranium. Over the past few years, ultrasound has gained increased popularity in its ability to diagnose acute fractures in the immature skeleton of children. Because many pediatric fractures are managed non-operatively, many practitioners are using bedside ultrasound to not only make the diagnosis, but also to aid with reduction and splinting.
10. PRACTICE: Remember that practice makes perfect. With bedside ultrasound there is no substitute for experience. The more ultrasounds you do, the better you will be able to differentiate abnormal from normal, even when you may not be sure exactly what the abnormality is.
Brady Pregerson manages a free on-line EM Ultrasound Image Library and is the author of the Tarascon Emergency Department Quick Reference Guide. For more information visit www.EMresource.org.
Teresa S. Wu is the Associate Residency Director, and Director of Ultrasound and Simulation Based Training for the Maricopa Emergency Medicine Program in Phoenix, Arizona.