SAEVA Congress 2018 Proceedings | 12-15 February 2018 | ATKV Goudini Spa
facilitates obtaining a good quality ultrasound image. The application of alcohol or
emu oil to the skin also is useful in obtaining a good image when clipping the hair on
the limb is not an option. After cleaning the skin a liberal application of ultrasound
transmission gel is necessary to provide an air free interface between the transducer
and the skin surface.
Transducer Selection
A high frequency transducer with a standoff is usually necessary to obtain optimal
image quality of the structures immediately beneath the skin surface as it helps to
provide a more continuous contact surface for imaging the structures beneath. A 7.5-
18.0 MHz transducer is ideal for obtaining quality images of the flexor tendons or
ligaments in the horse and allows visualization of the structures up to 4 or 5 cm from
the skin surface. As most of the tendon is usually within 1 cm of the skin surface, this
choice of transducer selection and the standoff provide optimal image quality to
evaluate this structure. If using a machine with variable focusing, the focal zone should
be centered in the tendon or ligament being examined. A 13.0 – 18.0 MHz transducer,
if available, will result in superior resolution of these tendinous and ligamentous
structures.
Scanning Technique
The tendons and ligaments should be scanned in two mutually perpendicular planes
from their origin to insertion. The limb is scanned transversely initially (the scan plane
perpendicular to the structure's long axis). The tendon or ligament is displayed in its'
short axis cross-section and the location of the lesion can easily be visualized. The
cross sectional area of the lesion and tendon can be measured in each zone
throughout the tendon's or ligament's length (preferable) or mutually perpendicular
diameter measurements of the lesion and tendon can be made. The sagittal image
plane (the scan plane parallel to the long axis of the structure) can then be performed
to evaluate the pattern of fiber alignment. The exact length of the lesion as well as the
lesion's cross sectional area and the percentage of the tendon or ligament affected can
provide important prognostic information. Re-evaluation of the tendon or ligament as it
heals and reassessing the tendon and lesion cross sectional area at the precise site
that the previous measurement was obtained is also useful in evaluation of tendon and
ligament healing.
Scanning Zones
The tendons and ligaments can be measured in centimeters from a standard reference
point such as the point of the ergot or in each of the zones. There are 4 main zones for
scanning the pastern that are shorter in length than the zones in the metacarpus or
metatarsus (approximately 2 cm): proximal P1 (P1A), mid P1 (P1B), distal P1 (P1C),
and proximal P2. A fifth zone can be obtained in some horses at the level of mid P2.
P1A
In this zone (the proximal third of P1) the SDFT has a thin, half-moon shape in the
transverse plane, and is the most palmar/plantar structure. The oval DDFT lies
immediately dorsal to the SDFT and becomes symmetrically bilobed as it e