Stress Imaging of the Stifle 1312004). The device consisted of a radiolucent
platform where the thigh and crus regions are
constrained by adjustable fiberglass stays and
straps. Cranially or caudally directed forces can
be applied onto the mobile tibial component
of the device. In an experimental study, the
observed laxity on stress radiographs using the
device was significantly different between sti-
fles with intact CrCL, partially ruptured CrCL,
and completely transected CrCL. The main
advantages of the device include the ability to
more precisely control stifle flexion angle, and
consistent delivery of a known force. The device
has been used in several studies to help assess
the performance of novel stabilizing techniques
in experimental dogs. Whereas the type of force
applied by the aforementioned device applies a
cranial drawer force, a more recently described
device aims to induce tibial compression by
positioning the limb onto a radiolucent frame
and a series of adjustable pegs (Bhandalet al.
2008). The use of such a device eliminates the
need for a handler to be exposed to radiation
during tibial compression radiography. Unfor-
tunately, these devices are not widely or com-
mercially available as they lack any obvious
clinical utility.
Standing radiography
Unlike in humans, the forces generated dur-
ing standing alone are enough to consistently
induce substantial tibial translation in CrCL-
deficient dogs (Kimet al. 2011; Kimet al. 2012).
Thus, imaging of the stifle during standing can
be considered as another form of stress imag-
ing. A horizontally aligned radiographic beam
is centered over the stifle using a mobile X-ray
unit, with the cassette placed between the dog’s
pelvic limbs. The dog is gently restrained to
limit motion and promote a comfortable pos-
ture as the image is acquired (Figure 18.4).
Horizontal beam radiography has been used
to quantify subluxation during standing before
and after various surgical procedures. The main
advantage of standing radiography is that sub-
luxation is caused by intrinsic forces occur-
ring naturally rather than by an externally
applied force. This means that the abnormal
alignment observed with standing radiography
gives direct insight into the degree ofin vivo
Figure 18.4 Photograph of the set-up used to acquire a
horizontal beam radiographic view of the stifle. A
horizontally aligned radiographic beam is centered over
the stifle using a mobile X-ray unit, with the cassette or
panel placed between the dog’s pelvic limbs. The dog is
gently restrained to limit motion and promote a
comfortable posture as the image is acquired.dysfunction. One previous study used stand-
ing radiography to show that persistent sub-
luxation occurs in a subset of cases after stabi-
lization with tibial plateau leveling osteotomy
(Kimet al. 2012) and tibial tuberosity advance-
ment (Skinneret al. 2013). The technique is
labor-intensive, and generally requires a han-
dler to restrain the dog where there is radi-
ation exposure. The flexion angle cannot be
controlled. Therefore, alternative measures of
subluxation such as quantifying the distance
between the proximal and distal attachment
sites of the CrCL may be required to compare
cranio-caudal alignment between different time
points or views. This technique may also be
especially prone to errors caused by oblique
projections because the axial rotational position
of the stifle may be variable.Stress-MRI
Recently, a stress-MRI technique was described
in an ex vivostudy where a custom-made