Authors: Pige Charlene, Spriet Mathieu, Perez-Nogues Marcos, Katzman Scott, Le Jeune Sarah, Galuppo Larry
Journal: Equine veterinary journal
Summary
# Editorial Summary: 18F-Sodium Fluoride PET Imaging in Nonracehorse Fetlock Disease Whilst 18F-NaF positron emission tomography (PET) has proven valuable for evaluating racehorses with fetlock pathology, its application in nonracehorses remains largely unexplored. This retrospective analysis of 36 fetlocks (predominantly forelimbs) from 25 nonracehorses compared PET imaging findings with computed tomography (CT) to characterise the metabolic activity patterns associated with fetlock disease and pain. Increased 18F-NaF uptake clustered in predictable locations—the medial subchondral bone of the proximal phalanx and the dorsomedial and dorsosagittal distal metacarpal/metatarsal subchondral regions—with moderate correlation to sclerotic changes on CT, though PET proved notably superior at detecting proximal sesamoid bone (PSB) abnormalities (12/36 fetlocks versus 3/36 on CT). Critically, maximal standardised uptake values (SUVmax) were significantly higher in clinically painful fetlocks (mean 22.0) compared to nonpainful ones (mean 11.9), suggesting that metabolic activity intensity, not merely the presence of structural change, carries clinical significance. For practitioners, this indicates that PET's capacity to quantify bone remodelling activity may better inform prognosis and treatment decisions than anatomical imaging alone, particularly regarding PSB involvement, and that SUVmax values warrant consideration when interpreting imaging findings in relation to clinical lameness.
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Practical Takeaways
- •18F-NaF PET is more reliable than CT for detecting fetlock pathology in nonracehorse populations, with better consistency between observers
- •PET is particularly superior to CT for identifying early proximal sesamoid bone changes, which may be clinically relevant to lameness assessment
- •Quantitative SUVmax values from PET can help distinguish clinically significant lesions from incidental findings when assessing painful fetlocks
Key Findings
- •18F-NaF PET showed higher interobserver agreement (0.62) compared to CT (0.47) for fetlock imaging in nonracehorse populations
- •Increased 18F-NaF uptake was most common in medial subchondral bone of proximal phalanx (23/36) and dorsomedial metacarpal/metatarsal distal subchondral bone (20/36)
- •PET detected abnormalities in proximal sesamoid bones (12/36) more frequently than CT (3/36, p=0.02)
- •Maximum standardized uptake values were significantly higher in painful fetlocks (22.0) compared to nonpainful fetlocks (11.9, p=0.038)