Histopathology in horses with chronic palmar foot pain and age-matched controls. Part 2: The deep digital flexor tendon.
Authors: Blunden, Dyson, Murray, Schramme
Journal: Equine veterinary journal
Summary
# Editorial Summary: Deep Digital Flexor Tendon Pathology in Chronic Palmar Foot Pain Blunden and colleagues examined histological changes in the deep digital flexor tendon (DDFT) from horses with chronic palmar foot pain compared to sound age-matched controls, investigating whether degenerative changes correlate with lameness severity and other structures implicated in navicular disease. Using tissue samples from the DDFT spanning from the proximal interphalangeal joint to its insertion point, the researchers graded lesion severity across multiple sites and assessed relationships with pathology in the navicular bone, associated ligaments, bursa, and distal interphalangeal joint structures. Significantly, dorsal layer abnormalities of the DDFT distinguished lame horses from controls, whereas palmar-aspect lesions did not; moreover, specific correlations emerged between the superficial dorsal DDFT and the flexor aspect of the navicular bone, and between deep dorsal DDFT changes and the proximal navicular bone and medulla. The navicular bursa showed strong correlation with degenerative changes across multiple DDFT layers, suggesting the bursa may be a common site of pathological involvement; notably, age alone did not predict lesion severity, indicating that lameness history rather than chronological age drives tissue degeneration. For practitioners, these findings support the concept that DDFT pathology commonly accompanies navicular disease and may represent early vascular and matrix changes preceding structural failure of the navicular bone itself—highlighting the importance of imaging and palpating the DDFT in cases of chronic palmar foot pain, and suggesting that future therapeutic strategies targeting tendon vascularity and matrix composition could offer new avenues for managing this frustratingly prevalent condition.
Read the full abstract on PubMed
Practical Takeaways
- •DDFT pathology is commonly present alongside navicular bone lesions in lame horses; diagnostic imaging should assess both structures systematically
- •Dorsal DDFT changes appear more significant than palmar changes in chronic palmar foot pain, which may inform therapeutic targeting
- •Early intervention addressing vascular and matrix integrity of the DDFT may potentially prevent or slow progression of navicular disease pathology
Key Findings
- •Significant histological differences in dorsal layers of DDFT exist between lame and control horses, but not in palmar aspect lesions
- •Strong associations found between superficial dorsal DDFT lesions and flexor aspect of navicular bone, and between deep dorsal DDFT and proximal border/medulla of navicular bone
- •Navicular bursa grade correlated with superficial dorsal, deep dorsal, and deep palmar DDFT layers
- •Vascular and matrix changes in DDFT may precede fibrocartilage changes in navicular bone, suggesting these are primary pathological events