Gross and histological evaluation of early lesions of navicular bone and deep digital flexor tendon in horses

The study aimed at evaluation of pathological lesions on flexor surface of navicular bone and deep digital flexor tendon in horses graded in standard X-ray examination as 2 (fair). The evaluation was performed on fifteen horses (6-9 years of age). Analysis procedure involved examining navicular bones on X-ray pictures, post-slaughter preparation of navicular bones from the hoof capsule, macroscopic evaluation of fibrocartilage on flexor surface, and analysis of histologic preparations. In horses with navicular bones graded as 2, early pathological changes have already developed, even if such horses were not lame. The pathological changes included fibrillation and disruption of deep digital flexor tendon surface, loss of fibrocartillage in sagittal ridge area of navicular bone, thinning of subchondral bone on its flexor surface, and fibromyxoid changes in chondroid matrix. In terms of clinical relevance, more studies are needed to understand the sequence of changes in a better way.