Identification of Heterotopic Mineralization and Adjacent Pathology in the Equine Fetlock Region by Low-Field Magnetic Resonance Imaging, Cone-Beam and Fan-Beam Computed Tomography.
Authors: Lin Szu-Ting, Peter Vanessa G, Schiavo Stefano, Pokora Rachel, Patrick Hayley, Bolas Nick, Foote Alastair K, Sargan David R, Murray Rachel C
Journal: Journal of equine veterinary science
Summary
Heterotopic mineralization (HM) in the equine fetlock has long been dismissed as clinically irrelevant, yet little objective data exists about its imaging characteristics or associated soft tissue damage. Researchers examined 12 cadaver limbs and retrospectively reviewed standing horse images using cone-beam CT, fan-beam CT, and low-field MRI, correlating findings with gross pathological examination. Both CT modalities identified twelve discrete mineralizations—most commonly affecting the oblique sesamoidean ligament (five cases without macroscopic change) and suspensory branch (six cases with documented pathology)—whilst MRI proved less sensitive for detecting mineralization itself but excelled at revealing concurrent soft tissue injury including ligament splitting, discoloration, and oedema (T2/STIR hyperintensity). The findings challenge the assumption that HM is merely incidental; cases involving the suspensory apparatus showed consistent structural disruption and inflammatory changes, suggesting these lesions warrant investigation and may influence prognosis and ridden work. For clinical practitioners, this work demonstrates that multimodal imaging—combining CT's superior mineralization detection with MRI's soft tissue characterization—provides the most complete assessment when HM is suspected, particularly in performance horses presenting with subtle fetlock dysfunction.
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Practical Takeaways
- •CBCT should be preferred when heterotopic mineralization in the fetlock is suspected, as it reliably detects lesions that MRI may miss; however, MRI adds critical information about associated soft tissue damage that affects prognosis and treatment.
- •Suspensory branch mineralization frequently occurs with ligament splitting and discoloration—findings that carry clinical significance for lameness assessment and may warrant conservative management or specific rehabilitation protocols.
- •Use multimodal imaging (CT plus MRI) for comprehensive evaluation of fetlock pathology in performance horses with unclear lameness, as each modality provides complementary diagnostic information.
Key Findings
- •CBCT and FBCT identified 12 heterotopic mineralizations with high sensitivity; CBCT found 5 in oblique sesamoidean ligament (no macroscopic abnormality) and 6 in suspensory branch (with macroscopic abnormalities).
- •MRI failed to identify all mineralizations but detected associated soft tissue pathology including suspensory branch splitting and T2/STIR hyperintensity in 4 suspensory branches and 3 oblique sesamoidean ligaments.
- •Both CT systems were superior to MRI for detecting heterotopic mineralization, while MRI provided unique information on soft tissue damage that may guide clinical management decisions.
- •All 7 ossified fragments were identified by CT; MRI best visualized fragments on T1 images with associated T2/STIR hyperintensity indicating ligament disruption.