Radiographs may overestimate C7–T1 joint size in horses: full analysis

A new Equine Veterinary Journal study adds an important caution for clinicians interpreting equine cervical imaging: lateral radiographs significantly overestimate the size of the C7–T1 articular processes compared with standing cone beam computed tomography in horses. In the retrospective study of 94 horses, Justine M. Cianci and co-authors found that CBCT-based measurements tracked osteoarthritis grades better than radiographic measurements, suggesting that apparent enlargement on radiographs may not reliably represent the true extent of pathology at the cervicothoracic junction. (pubmed.ncbi.nlm.nih.gov)

That finding lands in a part of the equine neck that already draws outsized clinical attention. Prior imaging and postmortem work has shown that bony changes in the cervical articular process joints are common, and that the caudal cervical spine, including C6 through T1, is a frequent site of modeling, flattening, osteophyte formation, and osteoarthritis. A recent study in Warmblood horses with neck-related signs found severe modeling of the articular processes at C7–T1 was more likely in cases than in controls, reinforcing that this region can be clinically relevant, not just radiographically conspicuous. (pmc.ncbi.nlm.nih.gov)

The technical issue is familiar to radiologists: projection imaging compresses three-dimensional anatomy into a two-dimensional view. In the caudal cervical spine, where anatomy is complex and positioning can be challenging, that can create misleading impressions of joint size or contour. Earlier work on equine caudal cervical radiography emphasized the need for standardized technique and noted that oblique views can add information beyond standard lateral projections. Other research has also reported low sensitivity of latero-oblique radiography for cervical articular process osteoarthritis when compared with CT or postmortem findings, underscoring the limits of radiography alone for these joints. (pubmed.ncbi.nlm.nih.gov)

Standing CBCT helps address some of those limits by providing cross-sectional imaging in sedated horses, avoiding the superimposition inherent to radiographs and, in many settings, avoiding general anesthesia. Published experience with standing CT and CBCT in horses has highlighted the appeal of faster imaging, lower procedural risk, and growing availability for head, neck, and distal limb workups, although image quality can still be affected by motion artifact and field-of-view constraints. In other words, CBCT is not perfect, but it offers a more anatomically faithful view of the caudal cervical articular process joints than a single lateral radiographic projection. (pubmed.ncbi.nlm.nih.gov)

Direct outside commentary on this specific paper was limited in publicly available sources, but the broader literature points in the same direction. Investigators have previously linked standing cone beam CT evidence of caudal cervical articular process joint osteoarthritis with inflammatory cytokine changes in synovial fluid, lending support to the clinical significance of lesions identified on advanced imaging. That doesn’t mean every enlarged-looking joint on a radiograph is incidental, but it does strengthen the case for confirming questionable or high-stakes findings with cross-sectional imaging when available. (pubmed.ncbi.nlm.nih.gov)

Why it matters: For veterinary professionals, the practical takeaway is less about replacing radiographs and more about recalibrating confidence in what they show at C7–T1. If lateral radiographs systematically overestimate articular process size, clinicians may risk overstaging disease, anchoring too heavily on apparent enlargement, or making treatment and prognosis decisions on anatomy distorted by projection. In horses with neck pain, stiffness, forelimb lameness, poor performance, or neurologic signs, that distinction could affect whether a case is managed conservatively, referred for advanced imaging, or worked up for other causes. (pubmed.ncbi.nlm.nih.gov)

The study also fits a broader shift in equine practice: advanced standing imaging is moving from referral-only novelty toward a more routine decision point in selected cases. As more hospitals add standing CT or CBCT capability, the threshold for confirming caudal cervical findings may fall, especially when radiographs and clinical signs do not line up. For veterinarians, that could mean a more nuanced imaging pathway, with radiographs remaining the first pass, but CBCT increasingly serving as the tie-breaker for the cervicothoracic junction. (dvm360.com)

What to watch: The next step is whether this measurement bias changes imaging protocols, referral patterns, or interpretation guidelines for suspected caudal cervical osteoarthritis, particularly at C7–T1, where radiographic appearance and true osseous change may diverge the most. (pubmed.ncbi.nlm.nih.gov)