Читать книгу Fractures in the Horse - Группа авторов - Страница 104

The advantages of ultrasonography over other imaging modalities include the practicality of being a patient side tool, it does not involve ionizing radiation, the acquisition is real time and it can be used in a dynamic manner.

Bone surfaces reflect approximately two‐thirds of incident acoustic waves, and the other one‐third is absorbed. Reflection is caused by the large difference in acoustic impedance between bone and surrounding soft tissues. The surface of compact bone creates a smooth, hyperechoic, continuous contour with strong acoustic shadowing artefact. The latter ordinarily produces a ‘clean’ shadow as absorption of the incident ultrasound beam at the bone surface is larger than the beam width [45, 46]. Discontinuity in compact bone is necessary for positive fracture identification. However, in the acute phase, secondary signs of bone trauma such as soft tissue swelling, fluid accumulation around the cortex/periosteum and haematoma formation are also useful findings. In the subacute phase identification of periosteal callus and entheseous new bone can also be helpful.

Ultrasound is commonly used to identify suspected pelvic (Chapter 33) and rib (Chapter 35) fractures and other locations not amenable to radiography. It is also utilized to assess concomitant injuries to soft tissues and/or synovial cavities.