Advances in the Canine Cranial Cruciate Ligament, 2nd edition

(^18) Stress Imaging of the Stifle
Stanley E. Kim
Introduction
Plain radiography is an excellent diagnostic tool
for evaluating stifles for cruciate ligament rup-
ture (CR) (Carobbi & Ness 2009). Stress imaging
for dogs with CR is not commonly performed,
as the most clinically significant information is
typically found when high-quality plain radio-
graphs are evaluated, together with accurate
clinical findings such as signalment, history,
and orthopaedic examination. However, stress
imaging of the cranial cruciate ligament (CrCL)-
deficient stifle still does carry some value in
both clinical and research settings.
The detection of excessive cranial tibial trans-
lation is pathognomonic for CrCL insufficiency.
Instability is classically assessed by examina-
tion using two physical tests: the cranial drawer
test (Muir 1997); and the tibial compression
test (Henderson & Milton 1978). Unfortunately,
it can be difficult to elicit a positive result
with either of these tests in dogs with CR, as
laxity may be overcome by factors such as poor
execution of the maneuver by the operator,
high muscle tone, and periarticular fibrosis in
the dog (Flo & DeYoung 1978). In some dogs
with partial CR, no palpable laxity is present
because the vast majority of the CrCL remains
intact. Thus, a non-operative diagnosis of CR
often relies on other examination findings such
as periarticular thickening, stifle effusion, and
pain. The simple combination of palpating the
stifle for the presence of effusion and detecting
stifle effusion on radiographs was shown to be
a highly accurate method for diagnosing CR.
Nevertheless, stress radiography has been
advocated to improve diagnostic accuracy by
quantifying cranial tibial translation radio-
graphically. This can be achieved by acquiring
radiographs while performing a modified tib-
ial compression test (de Roosteret al. 1998; de
Rooster & van Bree 1999a–c). Laxity may also
be detected on radiography by using specially
designed devices that attempt to force the stifle
into drawer (Lopezet al. 2004). Standing radio-
graphy may be considered as another ‘stress-
radiographic’ technique, where the intrinsic
forces that are present during standing promote
cranial tibial translation in CrCL-deficient sti-
fles (Kimet al. 2011). Finally, stress magnetic
resonance imaging (MRI) of the stifle has been
described for the purposes of evaluating menis-
cal integrity in CR stifles.
This chapter will outline each of these stress
imaging techniques and discuss their poten-
tial clinical and research utility. It should be
noted that coronal instability (i.e., assessment
of varus/valgus laxity), which typically occurs
Advances in the Canine Cranial Cruciate Ligament, Second Edition. Edited by Peter Muir. © 2018 ACVS Foundation.
This Work is a co-publication between the American College of Veterinary Surgeons Foundation and Wiley-Blackwell.
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