Radiographs may overestimate C7–T1 joint size in horses

Lateral radiographs appear to make the C7–T1 articular processes look larger than they are when compared with standing cone beam computed tomography, according to a retrospective Equine Veterinary Journal study of 94 horses by Justine M. Cianci and colleagues. The study found that radiographic measurements significantly overestimated articular process size at C7–T1, while measurements from standing CBCT aligned more closely with osteoarthritis grading on CBCT. That matters because the caudal cervical region, especially C7–T1, is already recognized as a common site of clinically relevant bony change in horses, and cross-sectional imaging is increasingly being used to evaluate these joints without general anesthesia. (pubmed.ncbi.nlm.nih.gov)

Why it matters: For equine veterinarians, the paper is a reminder that superimposition and projection effects on lateral radiographs can distort the apparent size of caudal cervical articular processes, particularly at the cervicothoracic junction. In practice, that means radiographs may be useful for screening, but they may overcall enlargement at C7–T1 and may not reflect the severity of osteoarthritic change as accurately as standing CBCT. Earlier work has already shown that advanced imaging can reveal clinically important caudal cervical joint pathology, with abnormalities often reported from C5 through T1 and severe modeling at C7–T1 associated with horses showing primary neck-related signs. (pubmed.ncbi.nlm.nih.gov)

What to watch: Expect more discussion around when standing CBCT should be used to confirm equivocal radiographic findings in horses with suspected caudal cervical osteoarthritis, neck pain, stiffness, poor performance, or neurologic concerns. (aaep.org)