Ultrasound uses high-frequency sound waves to generate real-time dynamic images that are used to evaluate and elucidate both normal and abnormal anatomical structures in horses. This same tool is also used to assist in treatments and procedures throughout the equine body.
The real-time nature of ultrasound allows visualization of needles as they penetrate the body and are simultaneously advanced toward a target. Sonography also allows visualization of sensitive structures that should be avoided during a procedure. Ultrasound guidance thereby improves the accuracy of treatments, plus distribution of the treatment material can be observed at or in the target.
Targets include almost any anatomical structure, fluid-filled structures such as joints, tendon sheaths, bursas or abnormal fluid-filled structures such as cysts. The guidance can be used for both placement of treatment substances or for aspiration of fluid for analysis or as part of the treatment.
More recently, ultrasound guidance has also been used to assist the direct intralesional placement of orthobiologic substances such as extracellular matrices, stem cells and platelet-rich plasma into tendons, ligaments, muscles, joints, tendon sheaths and bursas.
Stem cells are also administered via an intra-arterial route (i.e., via the median artery), and the author feels this should not be attempted without ultrasound guidance.
No matter what is being treated, accurate placement with sonographic guidance will improve treatment outcomes.
Ultrasound-guided local anesthesia is a prime example of the importance of accuracy. Nerve blocks and structural blocks (i.e., joints, tendon sheaths and bursas) are highly accurate with sonographic guidance, especially with deeper structures. The practitioner can avoid contact with target nerves—preventing unnecessary pain—and blood vessels—preventing excessive bleeding.
The median nerve of the forelimb is an excellent example. It is a deep structure that cannot be “blocked” accurately without this guidance. Contacting this nerve can elicit an extreme reaction by the patient, and the large median artery and veins are very close to the nerve. There is also a dense fascia that will prevent the block from working if the anesthetic is not placed within its confines. Ultrasound-guided local anesthesia is much more accurate than external “landmark” guided “blocking,” preventing possibly having to re-perform the procedure.
Ultrasound guidance can be used to perform standing cerebrospinal fluid acquisition at the atlanto-occipital space and the atlantoaxial space, though it is safest at the atlantoaxial space. Sonography permits visualization of the spinal cord and the adjacent blood vessels, allowing the practitioner to avoid needle contact of the cord and avoid blood vessels that would cause blood contamination of the sample.
Sonography can also be used for procedures such as biopsies of abnormal tissues and retrieval of foreign bodies. Again, this significantly improves the accuracy of the procedure and helps practitioners to avoid adjacent sensitive structures.
About the Author
Cooper Williams, VMD, DACVSMR, Certified ISELP Instructor, grew up in Cecil County Maryland, where he learned to play polo and train polo ponies with his family. He ultimately obtained a five goal rating and played professionally for five years. In the summer of 1981, he was a member of the United States polo team that competed throughout England. He coached the Valley Forge Military Academy polo team from 1981 to 1985. In 1984, he graduated with honors from the University of Pennsylvania School of Veterinary Medicine. He accepted a post graduate internship at Delaware Equine Center, where he developed their ultrasound imaging program. In 1987, he moved to Maryland where he worked for two years at Maryland Equine Center, also developing their ultrasound program. In 1989, Williams started his own practice, focusing on diagnostics and sports medicine in equine athletes. After three years of rigorous study, learning in depth about advanced diagnostic imaging, Williams passed his examination and was certified by the International Society of Equine Locomotor Pathology (ISELP) in 2009 and has continued on as a certified instructor with ISELP, teaching other equine veterinarians all over the world. Cooper is one of a small group of veterinarians in the world who is certified by the International Society of Equine Locomotor Pathology in advanced ultrasound imaging. In August 2014, Williams successfully passed his examination and is officially a Diplomate of the American College of Veterinary Sports Medicine and Rehabilitation. There are only a small group of veterinarians in the world that now can claim they are a specialist in sports medicine and rehabilitation. He is an active member of the North American Regenerative Medicine Association as well as being on the veterinary advisory board for ACell, Inc., a tissue engineering company.
Williams is a paid advisor for Butterfly Network.