Comparison between radiological and magnetic resonance imaging lesions in the distal border of the navicular bone with particular reference to distal border fragments and osseous cyst-like lesions.
Authors: Biggi, Dyson
Journal: Equine veterinary journal
Summary
# Editorial Summary: Radiographic Detection of Navicular Bone Lesions Biggi and Dyson (2010) sought to establish how reliably conventional film and computed radiography detect distal border fragments of the navicular bone compared with MRI, which served as the diagnostic gold standard. Forty-six fragments were identified on MRI in horses with foot lameness, yet conventional radiography detected only 18 of these (39% sensitivity), with computed radiography performing similarly at detecting 17 of 45 MRI-identified fragments—indicating no clinically meaningful difference between the two radiographic modalities. Large fragments (grades 4–5) were detected radiologically far more frequently than small lesions, and importantly, radiographic findings of distal border fragments showed significant correlation with concurrent MRI abnormalities in that region. Whilst both radiographic techniques demonstrated high specificity (meaning positive findings are reliable), their poor sensitivity means that negative radiographic findings do not exclude distal border pathology; practitioners should maintain a low threshold for MRI when navicular disease is suspected despite inconclusive radiographic appearances, particularly in cases of persistent foot lameness, as smaller fragments and early-stage lesions will likely be missed on conventional imaging alone.
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Practical Takeaways
- •If a distal border fragment is visible on radiographs, it is likely to be significant and associated with other navicular pathology; however, absence on radiographs does not rule out smaller fragments—MRI may be warranted for complete evaluation
- •Small or low-grade navicular fragments will be missed on standard radiography; practitioners managing subtle navicular cases should consider MRI for definitive diagnosis
- •Conventional film and digital radiography are equally unreliable for detecting small navicular lesions, so upgrade to digital does not improve fragment detection
Key Findings
- •Conventional and computed radiography showed similar low sensitivity (39% in Group A, 38% in Group B) but high specificity for detecting distal border fragments compared to MRI as gold standard
- •Large-sized (Grades 4-5) fragments were identified radiologically in most cases, while low-grade fragments were rarely detected
- •46 and 45 fragments were identified on MRI in Groups A and B respectively, compared to only 18 and 17 on radiographs
- •Radiologically identified fragments showed significant correlation with other pathological abnormalities of the distal border of the navicular bone on MRI