Ultrasound examination of the fetlock joint region can be performed in horses whose lameness has been localized to the fetlock joint region via intra-articular anesthesia, regional anesthesia (low 4- or 6-point nerve blocks) or regional swelling. Ultrasound examination should be performed in concert with fetlock radiographs and is indicated when radiographs are normal, if radiographic findings are not commensurate with the degree of the horse's lameness or when findings suggest predominant soft tissue injury. Additionally, fetlock ultrasound is indicated in horses that sustain wounds to the region as ultrasound can readily identify communication with synovial structures as well as evidence of osteomyelitis earlier than radiography. Lastly, ultrasound is useful to further characterize fractures seen on radiographs, aiding in surgical planning. The fetlock ultrasound exam includes evaluation of the superficial and deep digital flexor tendons as they course over the region, the medial and lateral suspensory branches, the intersesamoidean ligament, the oblique distal sesamoidean ligament origins and the superficial and deep components of the medial and lateral collateral ligaments. The exam also includes the bony surfaces of the distal metacarpus/tarsus, proximal PI and the axial and abaxial surfaces of the proximal sesamoid bones. The fetlock examination is performed with a high frequency linear transducer (13-18MHz) and can often be performed in its entirety without the use of a stand off pad.
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