[Scanning electron microscopic findings of the navicular bone and deep flexor tendon in podotrochlosis of horses].
Authors: Drommer, Damsch, Winkelmeyer, Hertsch, Kaup
Journal: DTW. Deutsche tierarztliche Wochenschrift
Summary
Podotrochlosis, commonly termed navicular syndrome, remains a significant cause of forelimb lameness in horses, yet its pathogenesis remains incompletely understood. Drommer and colleagues used light and scanning electron microscopy to examine the podotrochlear apparatus in 49 forelimbs from 25 horses, stratifying animals into three groups: those with clinical podotrochlosis, deep flexor tendon pathology alone, and clinically sound controls. Microscopic examination revealed extensive degenerative changes in affected horses—including cartilage and tendon matrix loss, collagen fibril denudation, necrosis, fissuring and significant surface defects—that were often absent or minimal on radiographs, suggesting that radiographic assessment substantially underestimates the true extent of soft tissue pathology. The morphological distribution of lesions indicated that initial damage originates at the deep flexor tendon surface from repetitive microtrauma and progressively extends to the navicular bone's flexor cortex, with cartilage and synovial involvement being secondary rather than primary. For practitioners managing navicular cases, these findings underscore the value of advanced imaging (ultrasound, MRI) in detecting early degenerative changes and suggest that therapeutic interventions targeting the deep flexor tendon–navicular bone interface may be more mechanistically sound than those assuming primary osseous or articular disease.
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Practical Takeaways
- •Radiographic normality does not exclude significant navicular bone or DDFT pathology—subclinical microscopic changes can be severe and warrant closer clinical monitoring and conservative management
- •The deep flexor tendon surface is the likely primary site of damage in podotrochlosis; management strategies should prioritize reducing repetitive microtrauma to this structure
- •Early detection and intervention targeting the tendon before navicular bone involvement occurs may alter progression and potentially preserve function
Key Findings
- •Podotrochlosis lesions consist of cartilage and tendon matrix loss with collagen fibril denudation, superficial degeneration, necrosis, fissures, and defects sometimes with tendon-bone adhesions
- •Light and scanning electron microscopy revealed moderate to severe pathological changes in radiologically normal or minimally altered tendons and navicular bones
- •Lesion distribution indicates initial pathology originates at the deep flexor tendon surface from repeated microtrauma and subsequently spreads to the navicular bone facies flexoria
- •Involvement of hoof joint cartilage and synovial layer in podotrochlosis was rare and considered secondary manifestation