Page 128 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.3 The foot 103

VetBooks.ir 1.179 1.180

Fig. 1.179 Navicular disease. Erosion on the flexor
cortex of the distal sesamoid.

Fig. 1.180 Adhesion between the flexor surface of
the distal sesamoid and the deep digital flexor tendon.

Fig. 1.181 T2*-weighted MR image of an erosion of 1.181
the flexor cortex of the navicular bone (arrow).

forms of navicular disease based on the pathology
and MRI appearance of lesions:

1 Degenerative disease of the palmar surface of
the navicular bone results in degeneration and
loss of fibrocartilage and cortical bone from
the flexor surface. This has been named ‘classic
navicular disease’. Secondary remodelling
changes in the spongiosa include oedema, venous
congestion and fibrosis of the marrow spaces,
trabecular thickening, focal osteolysis and
formation of osseous cyst-like lesions. Palmar 1.182
bone degeneration is frequently accompanied by
degenerative surface changes in the bursal part
of the DDFT and inflammatory synovitis of the
navicular bursa (Figs. 1.179–1.181).
2 Osseous fragmentation occurs at the lateral or
medial angles of the distal border of the navicular
bone. Distal border fragments may result in
remodelling changes of the adjacent cortical bone
and spongiosa at the distal border of the navicular
bone. Remodelling changes may include bone
oedema, focal osteolysis, sclerosis and formation of
osseous cyst-like lesions. Distal border fragments
may also result in a degenerative change in
the distal impar ligament. Remodelling and Fig. 1.182 T1-weighted MR image of a distal border
degeneration may eventually result in lameness, fragment and a corresponding concave defect at the lateral
although this is not seen in every case (Fig. 1.182). angle of the distal margin of the navicular bone (arrow).