Distal border fragments of the equine navicular bone: association between magnetic resonance imaging characteristics and clinical lameness.
Authors: Yorke, Judy, Saveraid, McGowan, Caldwell
Journal: Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association
Summary
# Editorial Summary: Navicular Bone Distal Border Fragments and Equine Lameness Improved MRI resolution has led to increasingly frequent detection of distal border fragments of the navicular bone, yet their clinical relevance remains poorly understood. Yorke and colleagues retrospectively analysed archived MRI studies from 453 horses (874 limbs) collected between 2006 and 2008, identifying 90 limbs (10.3%) with distal border fragments—predominantly located at the lateral aspect (62.2%) or involving both medial and lateral borders (28.9%)—and correlated these findings with recorded lameness severity using confidence interval comparisons and linear regression. The authors found no significant association between fragment presence and lameness status, no correlation between fragment volume and lameness severity, and only a marginally increased probability of lameness when bilateral medial and lateral fragments were present. These findings suggest that distal border fragments detected incidentally on MRI are unlikely to be primary drivers of clinical lameness, which has important implications for diagnostic interpretation: farriers and veterinarians should exercise caution against over-pathologising these fragments and consider concurrent soft tissue pathology (deep digital flexor tendon lesions, collateral sesamoidean ligament damage) or biomechanical factors when investigating navicular-region lameness. This distinction becomes increasingly critical as imaging sensitivity improves and incidental findings accumulate in clinical records.
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Practical Takeaways
- •Detection of a distal border fragment on MRI should not automatically be assumed to be the cause of a horse's lameness, as these fragments are not reliably associated with clinical signs
- •Fragment location and size alone do not predict lameness severity, so clinical evaluation must remain the primary diagnostic tool rather than relying solely on MRI findings
- •Incidental discovery of these fragments during MRI examination warrants caution in attributing clinical significance without supporting lameness evidence
Key Findings
- •Distal border fragments were identified in 13.25% of horses (60/453) and 10.3% of limbs (90/874) examined by MRI
- •50% of affected horses had unilateral fragments and 50% had bilateral fragments, with lateral location most common (62.2%)
- •No significant association was found between fragment presence and lameness classification, nor between fragment volume and lameness severity
- •Only horses with both medial and lateral fragments showed slightly increased probability of lameness classification