Page 177 - The Veterinary Care of the Horse

tendons and ligaments. The longitudinal scan shows the alignment of the tendon fibrils. In

this way, the extent and severity of a lesion can be seen (see figures 7.3a and b).
VetBooks.ir • The following measurements are made.

The site of the lesion.

• The length of the lesion.
• The cross-sectional area of the tendon or of a core lesion within it. The injured tendon is

usually enlarged in cross sectional area. As healing progresses, the diameter of the whole

tendon and of any discrete lesions visible within it reduce.
• The shape of the tendon. This may be altered if the lesion is restricted to one side of the

ligament or tendon.
• Any changes in the expected pattern of echogenicity showing if the tissue is more or less

dense than expected. Recently damaged tendons and ligaments generally appear darker
(less white) than normal due to disruption of the fibrils as a result of inflammation and

bleeding within the tissue. As healing progresses, the tissue regains a more homogeneous
appearance. If dense scar tissue forms or bone is deposited within the tissue during

healing, it will eventually appear whiter than it was originally on the image.
• Assessment of the alignment of the collagen fibrils in longitudinal images. These are

normally parallel and homogeneous in appearance. Where there is disruption as a result
of injury, the image initially appears darker and the fibres are no longer parallel. As

healing begins, the fibres will be randomly orientated and at this stage the tendon is
prone to re-injury. As healing progresses, the scar tissue remodels and the longitudinal

alignment improves. Assessment of this is important when advising on a programme of
controlled exercise.

With tendon and ligament injuries below the knee or hock, the opposite limb is usually

scanned at the same time. Very often both show evidence of wear and tear even if the injury
is only clinically apparent in one limb. The images are compared with each other and with

reference, i.e. ‘normal’, scans obtained from uninjured horses of similar type and size. The
images are recorded and stored for future reference and comparison.

Interpretation of the images

Producing quality images requires good technique as poor technique can make it look as
though a lesion is present in normal tissue. Vets sometimes refer to these ‘false’ lesions as

‘artefacts’. Interpretation requires detailed anatomical knowledge and experience. There are
various systems of grading the severity of changes seen on the ultrasound images and these