FIGURE 131.27 Hyperechoic spinous processes In most cases, the static technique is used to identify anatomical landmarks before the procedure It is feasible to use ultrasound in real time; however, there are challenges to the dynamic technique First, the procedure requires a sterile sheath and sterile gel Second, it may require a second person to hold the probe while the clinician performing the lumbar puncture inserts the needle In the dynamic technique, the probe is placed in the longitudinal axis and the needle inserted below the probe (Fig 131.30 ) This technique may be cumbersome for the novice sonographer Pitfalls The major pitfall with imaging the spine is being off axis Like the spinous process, the transverse process will also appear hyperechoic and may confuse the sonographer To avoid confusion, clinicians should scan side to side, and up and down, and ensure that the bony landmarks identified as the spinous processes are the most superficial Then the transverse view of the spine can confirm the image is midline and not off axis FIGURE 131.28 Neonatal spinal canal in long axis FIGURE 131.29 Neonatal spinal canal short axis SOFT TISSUE ULTRASOUND Soft Tissue Infections POCUS is useful for differentiating cutaneous abscesses from cellulitis in children presenting to the ED with soft tissue infections Ultrasound can also be used to identify the most fruitful site for incision into an abscess and to identify critical structures to avoid during incision (e.g., blood vessels and nerves), thereby minimizing procedural complications FIGURE 131.30 Photograph displaying dynamic technique for lumbar puncture FIGURE 131.31 Normal soft tissue Technique Most soft tissue structures are superficial and are best interrogated using a highfrequency linear transducer Scanning should extend from nearby uninvolved structures through the entire region of the affected area Images should be obtained in both the longitudinal and transverse planes Normal dermis and epidermis appear hyperechoic in relation to the deep subcutaneous fat globules (Fig 131.31 ) Fascia appears as a linear hyperechoic layer and muscle can be identified as hypoechoic cylindrical structures surrounded by hyperechoic perimysium (Fig 131.32 ) Interstitial edema in cellulitis is apparent as hypoechoic fluid separating the hyperechoic fat globules This effect is known as “cobblestoning” (Fig 131.33 ) Abscesses have a variable appearance, but most often are identified as anechoic or hypoechoic collections of fluid (Fig 131.34 ) Gentle compression of the abscess with the US probe can elicit fluid movement confirming the presence of a fluid collection ( Video 131.30 ) Pitfalls Cysts appear as anechoic structures with posterior enhancement and can be mistaken for abscesses However, they often have a more regular oval shape and not exhibit surrounding interstitial edema as seen in cellulitis Normal or