Page 363 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

338 CHAPTER 1

VetBooks.ir 1.663 1.664

Fig. 1.664 Transverse scan obtained from the
palmarolateral aspect of the pastern, immediately
distal to the base of the lateral PSB in a horse with
severe injury to the DSLs. The ODSL is enlarged
with loss of definition of its contours (yellow arrows).
Fig. 1.663 Similar view as in 1.657. This horse There is heterogeneous decrease in echogenicity.
sustained partial breakdown of the distal sesamoidean A small, avulsed bone fragment is visible (red arrow).
ligaments (DSLs). The short (deep) DSLs are ruptured
with frayed proximal fragments visible (yellow roughening and irregularity of the PSB surface at
arrows). The straight DSL was partially torn from the the ligament origin (Fig. 1.664). Chronic injuries
proximal scutum, with amorphous tissue filling the are more commonly encountered, with loss of nor-
space between the scutum and ligament (red arrow). mal fibre pattern and mineralisation (Fig. 1.665).
This was associated with fragmentation of the base of SDSL injuries are most often localised in the middle
the PSB (not visible in this image). portion of the ligament. A discrete, hypo- to anecho-
genic core lesion is visualised, although diffuse
Ultrasonography lesions are also encountered (Figs. 1.666, 1.667).
This is a difficult anatomical area to scan and may Rupture of the SDSL is uncommon but will be evi-
require some experience. Each ligament must be dent with complete loss of the ligament continuity,
approached specifically from the base of the PSBs. absence of fibre pattern and presence of a poorly
The use of a microconvex array transducer may delineated, hypoechogenic and heterogeneous area
be helpful to evaluate the short and cruciate DSLs separating the frayed proximal and distal portions
(Fig. 1.657). The affected ligaments are mark- of the ligament (Fig. 1.668). Chronic lesions are
edly enlarged, they appear hypoechogenic and het- characterised by a marked increase in CSA, loss of
erogeneous, and there is usually evidence of bone normal fibre alignment, abnormal heterogeneity and
remodelling at the sesamoidean and phalangeal hyperechogenic foci. Focal, ectopic mineralisation
insertion areas in chronic cases. Complete rupture may be present. This may occasionally be an inci-
is rare and is usually associated with either com- dental finding but probably represents an old lesion
plete DSL breakdown or fracture of the base of that was overlooked.
the PSBs (Fig. 1.663). ODSL desmitis presents as
obvious thickening and heterogeneous decrease in Magnetic resonance imaging and computed
echogenicity of the affected ligament(s), most often tomography
near the sesamoidean origin. They can affect one or MRI and CT may be useful to identify complex DSL
both ODSLs and are rarely bilateral. Lesions may injuries, and are most useful to look for proximal
be diffuse or discrete and there is usually marked DSL injuries.