Prepurchase examinations increasingly include cervical radiographs, which can identify various abnormalities. But of those radiographic lesions, which are clinically relevant? Which are likely to pose either a resale or an athletic risk?
Kathryn Bills, VMD, DACVR, DACVR-EDI, from the University of Pennsylvania’s New Bolton Center, tackled this topic at the National Alliance of Equine Practitioners’ (NAEP) 2024 Saratoga Equine Practitioners’ Conference, held Sept. 25-28, hoping to help practitioners weed out the relevant from the unimportant.
“It’s uncommon to get a totally normal neck radiograph,” she noted. “It’s important to appreciate that certain findings are associated with higher risk of future athletic performance, but others we aren’t so sure of.”
Moderate- to High-Risk Pathology
Bills relayed that the most important lesions in the neck include osteochondral (OC) fragments, osteoarthritis (OA) in young animals, and vertebral canal stenosis.
“There is a lower risk of these lesions affecting performance in older horses without concurrent OA or clinical signs,” she said. “The risk increases dramatically in a young horse, especially when accompanied by OA.”
Pro Tip: Look for OC fragments in the caudodorsal aspect of the cranial articular process and cranial aspect of the caudal process.
For OA, age certainly affects risk. Specifically, OA in the necks of young animals is concerning.
“The articular processes are large, and osteoproliferation obscures the intervertebral foramen,” said Bills.
But, she cautioned, be sure to look at positioning: “If the radiographs are crooked, this artifactually obscures the foramen. The consequence is that the horse’s neck may be normal, and the veterinarian may say the horse has osteoarthritis when it really doesn’t.”
Pro Tip: Don’t confuse a small foramen with obliquity.
In contrast to young horses, cervical OA in older horses is very common. It can be performance-limiting, but if the lesions are radiographically stable over time and there are no clinical signs, then the lesions are not particularly concerning.
Another concerning lesion is vertebral canal stenosis, diagnosed if the ratio of vertebral canal height to vertebral body height is less than 50%. Stenosis can occur at one site, but the risk of affecting performance increases when it occurs at multiple sites. Causes for stenosis can include caudal extension of the lamina over the intervertebral disc space, dorsal lamina dysplasia or osteoproliferation of the dorsal lamina, and intervertebral disc degeneration.
Double (or Triple) Trouble
Bills noted that we should be cognizant not only of individual lesions but also a combination of findings when assessing risk.
To demonstrate her point, she presented the case of a 3-year-old Hanoverian with a history of appendicular (in the limbs) osteochondrosis. Neck radiographs showed mild OA of C6-C7. Six weeks later, he was acutely ataxic, Grade 3 out of 5. Neck radiographs were repeated, and the horse was referred.
“The original interpretation of the X-rays was only mild C6-C7 OA,” Bills explained. “The degree of arthritis was actually greater in the opinion of myself and our neurologist, which is concerning in such a young horse. When the rDVM repeated the radiographs, they thought they identified a fracture, but it was actually an osteochondral fragment not associated with acute fracture. Additionally, the original review of the images did not identify that the horse had a region of canal stenosis. In combination, the OA, osteochondral fragment, and stenosis made cervical vertebral stenotic myelopathy a likely cause of clinical signs in this horse.”
Congenital Anomalies
In young animals, the term “congenital anomalies” refers to any deviation from normal. Veterinarians need to be aware of congenital anomalies because they occur relatively frequently, with a prevalence of about 24% to 38%.
“In most horses, congenital anomalies do not cause clinical signs. In the rare cases they do cause signs it is usually secondary to concurrent osteoarthritis,” Bills added.
Examples of congenital anomalies include:
- Homologous transposition where part of one or both C6 transverse processes are present on C7.
- Caudoventral lamina transposition. This is a hot topic right now, according to Bills, that could be clinically relevant because muscles attach to the lamina and might cause biomechanical issues.
- Vestigial ribs on C7 and absent ribs on T1.
“There is only an unsubstantiated resale risk when vestigial ribs are seen alone,” Bills said. “There are stories of horses being euthanized for this, but the peer-reviewed literature does not support this.”
Take-Home Message
Regardless of what you find, Bills said, “radiographic findings should always be correlated to the current and expected level of work, clinical exam findings, known medical history, and consideration of resale potential.”
Further, Bills encouraged veterinarians to perform a targeted neurologic evaluation or refer to a neurologist if radiographically concerning findings are identified that would predispose the horse to developing neurologic dysfunction.
Related Reading
- Managing Lumbosacroiliac Joint Region Pain in Horses
- Disease Du Jour: Nuchal Bursitis in Horses
- Approach to Horses with Poor Performance
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