46TH
ANNUAL
CONGRESS
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THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
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flexor tendons4. More recently, the use of ultrasound for the diagnosis of proximal
suspensory desmopathy has been challenged by MRI, as MRI provides better tissue
contrast and allows for the identification of more subtle pathology while
simaltaneously evaluating the osseous structures3.
Diagnostic Imaging – Nuclear Scintigraphy
Nuclear scintigraphy is invaluable for the assessment of tarsal region lameness.
Because scintigraphy provides functional information bone remodeling, it can
delineate between active and inactive radiographic findings or, identify active bone
remodeling when radiographic findings are absent7. When horses block to a deep
branch of the lateral plantar nerve block, abnormalities can exist in the proximal
metatarsus and in the distal, plantar aspect of the tarsus. These can be very difficult
to differentiate with routine imaging techniques. Horses with proximal suspensory
desmopathy (desmitis) often benefit from a technique that can evaluate the bone
physiology at the enthesis3,8,9.
Scintigraphy is critically important for the evaluation of stress (exercise induced)
remodeling, particularly in racehorses. Non-displaced, occult fractures of the
cuboidal bones and the talus 10 can occur with little or no radiographic abnormalities.
Often these fractures are first detected using scintigraphy. Scintigraphy’s limitations
are superimposition and its inherently low-resolution. It should be used in concert
with other diagnostic imaging techniques.
Diagnostic Imaging – Computed Tomography
Computed tomography an excellent modality for the evaluation of complicated
osseous structures such as the tarsus. CT has high spatial resolution, thin slices and
rapid acquisition. CT has been used to define abnormal regions of subchondral
bone11 and for further delineation of fracture in the tarsal region12. Because CT is a
cross sectional modality, visualisation of the normally ‘inaccessible’ portions of the
tarsus (talocalcaneal joint, tarsal sinus, intertarsal spaces) is possible. This technique
can be used to identify unusual sites of osseous trauma or joint disease. In the
proximal metatarsal region, osseous proliferation and lysis can be readily identified
when it occurs in conjunction with proximal suspensory disease. Intra-arterial,
regional contrast enhanced CT (CECT) via the cranial tibial artery aids in the
evaluation of regional soft tissues. CT can be a great aid to the diagnosis of proximal
metatarsal or tarsal lameness.
Diagnostic Imaging – Magnetic Resonance Imaging
Magnetic resonance imaging is useful for evaluation of the tarsus and particularly for
the proximal metatarsus3,9,13. Using MRI, osseous trauma, joint disease and soft
tissue injury can be detected. MRI has the added advantage of providing fluid
sensitive sequences to identify bone contusions or edema. While most publications
regarding MRI of the metatarsal region have discussed high field MRI, low field MRI is
also useful for this region. Standing MRI in this region is possible but can be a
frustrating exercise due to patient motion.
Summary
Tarsus imaging is an important component of lameness diagnosis in the horse. In
most cases, radiography and ultrasonography should be considered complementary
for complete evaluation of the functional unit. Other diagnostics including nuclear
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