Diagnosing and treating back pain is a notoriously difficult job for equine vets. Expert Andy Fiske-Jackson of the Royal Veterinary College and course organiser of The Equine Back explains why ultrasound should be used more frequently by vets investigating a painful back.
A secure diagnosis of back pain is difficult to reach. Clinical signs under saddle and pain on palpation will usually prompt diagnostic imaging of the area. In practice, this will usually be restricted to radiographs of the spinous processes in the thoracolumbar spine. However, the presence of impinging spinous processes is significantly associated with osteoarthritis of the articular process (facet) joints (APJs). The large muscle mass around the APJs reduces the ability of most portable x-ray machines to achieve diagnostic images of these areas. The diagnosis of impinging spinous processes is straightforward; a grading scale exists and a larger area of dorsoventral impingement between two spinous processes is associated with increased likelihood of pain.
Osteoarthritis of the APJs occurs either alone or in association with other bony abnormalities, especially impinging spinous processes. Lesions are most commonly seen in the caudal thoracic spine and best visualised on 20 degree oblique radiographs. It should be noted that the diaphragm and abdominal viscera further compromise the quality of images. The severity of clinical signs appears to be unrelated to lesion type or number but increases in the presence of impinging spinous processes. Nuclear scintigraphy can be used to further ascribe significance to bony abnormalities seen radiographically.
Ultrasound of the APJs is challenging, especially in thick set horses. In people and small animals computed tomography (CT) is the gold standard for assessment of bony pathology of the back. A recent study by Rhiannon Morgan compared CT and ultrasound for the diagnosis of APJ osteoarthritis in cadaver specimens. She found that the degree of periarticular remodelling of thoracolumbar APJs can be reliably assessed during an ultrasonographic examination from T14-L5 with agreement seen between ultrasonographic and CT grades. Therefore, difficult though it is, ultrasound of the APJs should form part of the assessment of back pain.
the equine back - 10 july 2021
Join us on Andy Fiske-Jackson's course at the RVC on 10 July to improve your diagnosis and treatment of back problems.
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