Effect of <scp>X</scp> ‐Ray Beam Angle and Superimposition on Radiographic Evaluation of Kissing Spines Syndrome
Authors: Djernæs J, Vedding Nielsen J, Berg L
Journal: Equine Veterinary Journal
Summary
# Editorial Summary: Radiographic Assessment of Kissing Spines Syndrome Kissing spines syndrome remains a significant diagnostic challenge in equine practice, with radiographic measurement of interspinous spaces forming a cornerstone of evaluation in clinical, sale, and insurance contexts. Djernæs and colleagues investigated two critical sources of error inherent to radiographic imaging: the effects of X-ray beam angle across the image field and the inevitable superimposition of three-dimensional anatomical structures onto two-dimensional radiographs. Using cadaver material from six horses (four with confirmed KSS, two normal controls), the researchers compared latero-lateral radiographic measurements against simultaneous CT and MR imaging of the thoracic dorsal spinous processes. X-ray beam angle significantly affected interspinous space measurements by up to 2 mm between positions only three vertebrae apart (P<0.02), whilst radiographic measurements consistently underestimated interspinous space widths compared to CT and MR by margins reaching 3 mm (P<0.0001 for both modalities). These findings have important implications for practitioners relying on radiographs for diagnosis: apparent narrowing of interspinous spaces may reflect geometric distortion rather than true pathology, standard radiographic positioning protocols may inadvertently introduce systematic bias, and cross-referencing radiographic findings with cross-sectional imaging should be considered in equivocal or borderline cases, particularly where treatment decisions hinge on precise measurement.
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Practical Takeaways
- •Radiographic measurements of interspinous spaces in KSS cases may underestimate actual spacing by up to 3 mm — use consistent beam angle positioning and consider supplemental CT/MR imaging for accurate diagnosis
- •When interpreting radiographs for KSS, account for measurement variability of up to 2 mm depending on beam angle and position within the image
- •Radiographic findings should be interpreted cautiously for KSS diagnosis; 2D imaging limitations may lead to false positives or misinterpretation of disease severity
Key Findings
- •X-ray beam angle significantly affected interspinous space (ISS) measurements with differences up to 2 mm between positions
- •Radiographic ISS measurements were significantly lower than CT measurements by up to 3 mm (P<0.0001)
- •Radiographic ISS measurements were significantly lower than MR measurements by up to 3 mm (P<0.0001)
- •Superimposition of anatomical structures on 2D radiographs leads to systematic underestimation of interspinous spaces compared to 3D imaging