Page 322 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.8 Soft-tissue injuries 297

VetBooks.ir 1.560 1.561

Fig. 1.561 A subacute, peripheral hypoechogenic
lesion on a cross-sectional (transverse) ultrasonographic
scan of the palmar aspect of the metacarpus.

Fig. 1.560 A subacute, hypoechogenic central periphery (Fig. 1.561), or anywhere in the tendon.
core lesion (arrows) on a cross-sectional (transverse) The size of the defect should be measured and its
ultrasonographic scan of the palmar aspect of the ratio to the whole cross-sectional area (CSA) of the
metacarpus. This is the most common site for lesions tendon can be calculated (most scanners have soft-
to occur. ware that make this possible). Longitudinal scans
should always be performed because they will show
the extent of the lesion and loss of the normal par-
1.562 allel fibre pattern. The latter gives an insight into
the normal fascicular organisation of tendon fibres
(Fig. 1.562).
Associated swelling of the tendon due to oedema,
haemorrhage and cell infiltration causes an increased
CSA. Some lesions may be more diffuse and less
defined (Fig. 1.563). Decreased echogenicity is due
to the loss of large enough interfaces. It can therefore
represent fluid, necrotic materials or poorly organised
immature tissue. Early haemorrhage is echogenic
because of aggregating cells in the thrombus. In fact,
it may be indistinguishable from surrounding, intact
tissue on cross sections (Figs. 1.564, 1.565). As the
cells are lysed, the haematoma organises and echo-
genicity decreases (Fig. 1.566). Early granulation
Fig. 1.562 Longitudinal, sagittal ultrasonographic tissue, made up of very small fibres, a gel-like water-
scan of the SDFT of a horse with subacute tendonitis. rich matrix, microscopic vascular buds and sparse
There is loss of the normal fibre alignment within the cells, remains hypo- to anechogenic (Fig. 1.560).
SDFT (arrowheads), which also appears significantly As the repair tissue matures, vessels and fibres orga-
enlarged and hypoechogenic. The underlying DDFT nise into large enough structures to cast echoes, thus
shows a normal echostructure. increasing the lesions echogenicity (Fig. 1.567).