Page 315 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

290 CHAPTER 1

VetBooks.ir necessary for some applications over areas covered 1.548
by large muscle masses (e.g. ilial wing fractures),
overlying irregular bony contours or to approach
structures that lie at an angle to the skin (e.g. intra-
articular ligaments, distal fetlock). They are also of
use to examine the palmar foot area, as the poorly
echogenic tissue in this area frequently significantly
attenuates higher frequency beams.
The hair should be clipped as finely as possible
(using a No. 40 or finer clipper blade) over the whole
area of interest. It is not necessary to shave the area
as this will often lead to skin damage and subsequent
swelling and pain. It is possible to scan a horse with-
out clipping, but the hair coat traps air and debris
and markedly attenuates the sound beam, causing Fig. 1.548 A low-field, open magnet MRI machine
major loss of information and artifacts. The use of used to acquire distal limb images. (Photo courtesy
surgical spirit helps to improve sound transmission Alex Font)
through the hair. A gel stand-off pad may be useful
in some irregular or curved areas.
Ultrasonography requires experience and a thor- • Conditions in the proximal plantar
ough knowledge of the normal anatomy for accurate metatarsus or palmar metacarpus, where it
interpretation of the images. Comparison with the provides significant information regarding
contralateral limb is always useful and will assist the the enthesis of the SL, underlying bone
operator in differentiating between normal varia- structures and peritendinous tissues.
tions in ultrasonographic appearance and significant • Soft-tissue lesions and complex bony
lesions. Beware, however, of bilaterally symmetrical abnormalities in the foot, for which it is
anomalies. considered the imaging technique of choice.
The technique is described in further details in • Portions of the flexor tendons and sesamoidean
the superficial digital flexor tendinopathy section ligaments located around the ergot area,
(p. 292). where ultrasonographic imaging may not be
adequate.
Other techniques
MRI has proved to be a very accurate means of MRI has been found to provide precise informa-
detecting and assessing soft-tissue lesions in the tion regarding the nature of soft-tissue injury and is
musculoskeletal system in the horse and coinci- particularly sensitive to detect haemorrhage. It may
dentally increased our understanding of associated be difficult, however, to distinguish acute from
pathology. The increasing access to the modal- chronic tendon injury. There still remains some
ity throughout the world, plus the improvements doubt regarding the significance of certain altera-
in technology, in particular low-field, open MRI tions on MRI and further large-scale studies are still
magnets allowing imaging in the standing horse required to improve specificity and correlate images
(Fig. 1.548), has rapidly expanded the use of MRI to the histological abnormalities in various tissues.
for soft-tissue limb injuries. It has proved very use- Furthermore, the technique necessitates an excellent
ful for imaging soft-tissue structures that may not knowledge of the technology to optimise acquisi-
be adequately visualised with other means, including tion protocols and specialist standard experience for
ultrasonography. In particular MRI has tremendous adequate interpretation.
potential diagnostic value for: