46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
5
underlying pathologic processes as compared to nuclear medicine images.
Radiography is useful for evaluation of the osseous column (joint space width,
phalangeal alignment, phalangeal position relative to the hoof capsule) and it provides
an overview representation of bone quality including marginal changes (osteophytes
and enthesophytes), cortical and medullary density alterations (lucency or sclerosis).
Radiographs still provide an excellent evaluation the navicular bone itself. Because of
advanced imaging techniques, it is now known that pathology of the navicular bone is
commonly associated with soft tissue pathology.
Therefore, radiographic
abnormalities of the bone should increase the clinician’s clinical suspicion of soft
tissue injury in certain cases18,19.
Furthermore, enthesis remodeling at the
attachment sites of the collateral ligaments of the distal interphalangeal can be
associated with collateral ligament injury20.
For this reason, radiograph
interpretation should include a careful evaluation of bone margins and entheses as
soft tissue injury can often be inferred by osseous abnormalities at sites associated
with specific soft tissues.
Diagnostic Imaging – Ultrasound
Diagnostic ultrasound is an important, readily available adjunct imaging technique.
Increased probe selection and image quality provide greater capabilities for diagnosis
of all anatomic regions. In horses with lameness that responds to a distal palmar
(plantar) digital nerve block, pastern21, transcuneal1 and distal interphalangeal
collateral ligament22 examination with ultrasound can be invaluable. In some
instances providing a clinical diagnosis that obviates the need for more advanced
techniques such as CT or MRI. The inability of ultrasound to penetrate the cornified
tissues of the hoof is the obvious shortcoming with this technology. Even
considering this limitation of the technique, alterations in size, shape, echogenicity
and margination can be detected in many critical anatomic structures of the foot.
For example, in the very distal portion of the pastern, where imaging of the deep
digital flexor tendon is off incident, alterations in size and margination are indicative
of a dorsal border abrasion21.
Diagnostic Imaging – Nuclear Scintigraphy
Nuclear scintigraphy remains the diagnostic imaging technology capable of providing
functional information regarding the underlying bone and to a lesser degree soft
tissue structures3,13,14. Nuclear scintigraphy is a sensitive test that has the ability to
differentiate sites of active remodeling from those that are inactive23. This technique
has proven to be very useful for the identification of navicular bone activity
(modeling or remodeling), either at enthesis sites or in the medullary cavity2.
Additionally, scintigraphy is valuable for the evaluation of ossified collateral cartilages
particularly when the degree of ossification is sufficient to increase the clinical
suspicion of distal phalangeal or collateral ligament injury14,24. This technology can
also be useful for tendon and ligament evaluation if local tissue disruption and
inflammation is sufficient to allow for technetium pooling in the injured soft tissue.
Scintigraphy’s limitations are superimposition and its inherently low-resolution
acquisition.
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