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The ultrasound transducer used is defined by the area to be evaluated. For long bones and flat bones, a linear transducer (7.5–13.0 MHz) is optimal. The elongated flat contact footprint and high frequency optimize the resolution of superficial structures. Although the long axis view is used, in some instances it can be technically easier to dynamically survey in short axis then use oblique and longitudinal views to build up information once the area has been localized. Rotating from long to short axis also helps to discriminate the bone cortex from other echogenic structures. Long axis evaluation can also assess angular and step displacement. Irrespectively, a second orthogonal plane is routinely used to complete fracture evaluation. Axial and most proximal appendicular structures can be assessed using alcohol/spirit contact. However, when assessing superficial, acute injuries, the probe should be placed gently using ultrasound coupling gel to minimize patient discomfort. Depending on the degree of soft tissue swelling, a stand‐off may be contributory, but this may be offset by patient sensitivity since the increased pressure used to produce reasonable contact may not be tolerated.

A convex low‐frequency (2.0–6.0 MHz) transducer is employed for deeper structures or if a wider field of view is required. There is a loss of axial resolution, but this does not usually inhibit fracture identification. When surveying ribs, a convex probe can be used first. The wide field of view enables more than one rib to be imaged which makes it easier to discern specific rib numbers. Once abnormalities are located, a linear probe with improved resolution can then be employed to assess displacement and/or callus formation.

Other transducers should be used as needed to evaluate specific structures. A micro‐convex transducer (4.0–10.0 MHz) may be required for assessment of the deep digital flexor tendon in horses that have sustained an accessory carpal bone fracture [47] (Figure 5.5) while, a linear rectal transducer (8.0–12.0 MHz) is used for transrectal evaluation of the pelvis, sacrum and caudal lumbar spine.