Use of radiography, computed tomography and magnetic resonance imaging for evaluation of navicular syndrome in the horse.
Authors: Widmer, Buckwalter, Fessler, Hill, VanSickle, Ivancevich
Journal: Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association
Summary
Conventional radiography has long struggled to reliably diagnose navicular syndrome in horses, as radiographic findings frequently fail to correlate with clinical signs, whilst scintigraphy produces both false positives and false negatives. Widmer and colleagues compared computed tomography (CT) and magnetic resonance imaging (MRI) against radiography and histopathological findings in cadaver specimens, examining how each modality visualised the navicular bone and associated soft tissues. CT and MRI revealed substantially more osseous pathology than radiography alone—including synovial fossa alterations, medullary opacification, cyst formation and bone remodelling—with CT providing the clearest definition of bony changes; critically, MRI identified soft tissue involvement of the deep digital flexor tendon, impar ligament and bone marrow that remained invisible on radiographs. The multiplanar and tomographic capabilities of both advanced imaging modalities enable detection of pathological changes earlier and more accurately than conventional radiography, supporting earlier intervention and more definitive diagnosis. For equine practitioners, these findings underscore that whilst radiography remains useful for screening, cross-sectional imaging—particularly CT for osseous detail and MRI for soft tissue characterisation—should be considered essential for comprehensive navicular evaluation, especially in cases where clinical signs persist despite unremarkable radiographic findings.
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Practical Takeaways
- •If navicular syndrome is suspected but radiographs appear normal or inconsistent with clinical signs, CT or MRI can reveal significant pathology not visible on conventional radiography and guide more targeted therapeutic decisions
- •CT provides superior bony detail while MRI excels at soft tissue visualization; consider requesting CT for osseous assessment and MRI for tendon and ligament evaluation of the navicular region
- •Radiographic changes alone should not be used to rule out navicular syndrome; advocate for advanced imaging when clinical signs persist despite normal or equivocal radiographic findings
Key Findings
- •CT and MRI revealed significantly more osseous changes than conventional radiography, with CT providing the clearest definition of bony remodeling including altered synovial fossae, medullary opacity changes, cyst formation and shape changes
- •MRI successfully identified histologically confirmed soft tissue alterations of the deep digital flexor tendon, impar ligament and marrow that were not visible on conventional radiography
- •Many osseous changes visible on CT and MRI were not radiographically evident, suggesting conventional radiography significantly underestimates navicular pathology
- •The multiplanar and tomographic capabilities of CT and MRI facilitate earlier and more accurate diagnosis compared to conventional radiography