30
46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
Maximising the Use of Ultrasound in
Clinical Practice
Christine Smith DVM, Diplomate ACVS, Agnes Banks Equine Clinic, 5 Price Lane, Agnes
Banks, NSW 2753 Australia.
Ultrasonography is an invaluable tool for evaluating lame horses, and its use should
not end with the traditional use of evaluating tendons and ligaments. The use of
ultrasound in the evaluation of joints and bones can add important information to
your evaluation and decision-making. I have found I have become increasingly reliant
on ultrasound, especially since moving to a practice that does not have MRI or CT
capabilities.
Ultrasound can be performed almost everywhere in the body and is relatively
inexpensive. Although digital radiology remains the usual first port of call when trying
to determine the source of lameness, it can be limited by anatomic location (i.e.
pelvis), the acuteness of the pathological process, and its inherent limitations to
identify lesions associated with the cartilage and soft tissues. If faced with a lameness
that has been localised to an articular structure or region, and radiographs fail to
yield a definitive diagnosis, I almost always reach for the ultrasound to give me
information about what is intra-articular versus peri-articular swelling, as well as gain
more information about the cartilage, joint capsule and synovium, in additional to
evaluation of peri-articular ligamentous structures.1-3 The stifle and fetlock joints are
excellent examples. Assessment of joint capsule, synovium, cartilage, collateral
ligaments will give the veterinarian far more information than radiographs alone will
yield. In the stifle patellar ligaments, collateral ligaments and peripheral menisci are
easily imaged, as are the annular ligament, collateral ligaments and intersesamoidean
ligaments in the fetlock joint.4-8 I also routinely use ultrasound when performing
arthrocentesis of the coxofemoral joint, shoulder or bicipital bursa.
In horses that present with generalised swelling, I use ultrasound to help differentiate
between primary cellulitis versus possibly septic joints with associated cellulitis. As
veterinarians we can be reluctant to tap synovial structures when there is a cellulitis
component, for fear of introducing infection into a non-septic joint. Septic joints or
tendon sheaths will typically be effused, with thickened joint capsule, and
proliferative synovitis. The synovial fluid may be more cellular, and hence appears
less hypoechoic than normal. It is worth remembering that many septic joints may
have little to no effusion ultrasonographically, the fluid may appear anechoic despite
high total nucleated cell counts, and the thickened synovium is the most consistent
finding.9 With cellulitis alone, the joint appears to have little effusion, the fluid is
hypoechoic, and the thickened tissues are confined to the subcutaneous regions. I
use ultrasound to help me decide which articular structures should be tapped in the
face of cellulitis as well as the best approach to minimise needle passage through
infected extra-capsular tissues. Using ultrasound to evaluate the tendons within a
septic tendon sheath is also very important in forming a prognosis for resolution of
infection and return to athletic function.
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