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Tips & Tricks for Musculoskeletal Ultrasound
1. Ultrasound can be used to augment clinical findings and help expedite the diagnosis in patients suspected of having a musculoskeletal injury
2. Large muscle injuries are usually easy to diagnose based on history and physical exam alone. Partial or small tears can be assessed via bedside ultrasonography.
3. Use the 7.5 to 10 MHz linear array transducer for visualization of superficial muscles. Large, deep muscles of the thigh or buttocks are best visualized using lower frequency probes.
4. The patient should be scanned in a position of comfort, allowing for full relaxation of the muscles in question.
5. The echotexture of normal skeletal muscle consists of a relatively hypoechoic background of muscle fascicles interspersed between hyperechoic strands of fibroadipose septa (Figure 1).
6. Scan along adjacent normal tissue planes to gain a better appreciation of what the patient’s normal muscles and tendons look like. Begin the scan away from the suspected area of injury and slowly work your way towards the most painful site.
7. Look for breaks in the normal muscle fibers or areas of hypoechoic edema or hematoma formation. The myotendinous junction is the weakest point along the muscle fibers, and is therefore the most common site of partial or complete muscle injury. Scanning around this site may demonstrate obvious tears, edema, or inflammation.
8. On bedside scanning, avulsion or retraction of the muscle fibers may be noted in proximity to the tendon or aponeurosis to which they attach. Contracted muscle will appear more hyperechoic than adjacent, normal fibers.
9. Remember that the angle between the ultrasound beam and the muscle is important. If the beams are not directed exactly perpendicular to the muscle fibers on the long axis view, hypoechoic artifacts may be seen and misdiagnosed as areas of injury or edema (anisotropy).
Brady Pregerson manages a free on-line EM Ultrasound Image Library and is the editor of the Emergency Medicine Pocketbook series. For more information visit EMresource.ORG.
Teresa S. Wu is the Associate Residency Director, and Director of Ultrasound and Simulation Programs and Fellowships, for the Maricopa Emergency Medicine Program in Phoenix, Arizona. She is an Associate Professor in Emergency Medicine at the University of Arizona, School of Medicine-Phoenix.