130 Clinical Features
(A) (B)Figure 18.3 Paired lateral
radiographs (neutral and tibial
compression) are obtained using
positioning illustrated by the
drawings. A standard lateral
radiographic view is obtained
with the joint at 90◦of flexion
(neutral position; A). While
maintaining the angle of flexion,
the tarsal joint is maximally
flexed by use of manual pressure,
and a second radiograph is
obtained (tibial compression
position, B). Source: Reproduced
from de Roosteret al. 1998, with
permission from the British
Veterinary Association.Evidence for the ability of tibial compression
radiography to diagnose partial CR is conflict-
ing. It has been suggested that performing the
tibial compression test at 90◦of flexion will be
able to induce abnormal cranial tibial transla-
tion even in those cases with partial CrCL rup-
ture, because the cranio-medial band is typ-
ically damaged and the intact caudo-lateral
band is lax in flexion. In a clinical study where
the change in femoro-tibial alignment between
stressed and non-stressed views was quantified,
significant differences in relative femoro-tibial
displacement were found between normal sti-
fles, stifles with partial CR, and stifles with com-
plete CR (de Rooster & van Bree 1999c). In a
more recent investigation, greater cranial tibial
translation was also identified in palpably sta-
ble stifles with mild CrCLfiber disruption when
compared to a control group (Zatloukalet al.
2000). However, an upper limit of normal lax-
ity has not yet been defined. Indeed, a surpris-
ingly wide range of laxity has been found for
joints with completely intact CrCLs. Results of
another clinical study corroborate that there is
a ‘gray-zone’ of laxity that includes both nor-
mal and diseased stifles. Furthermore, differ-
ences in the degree of fiber damage to the CrCL
and medial meniscus cannot be deduced from
the amount of relative displacement (de Rooster
& van Bree 1999c).
The inability to distinguish normal laxity
from subtly abnormal laxity is arguably one
of the major reasons why this test has not
become more widely adopted in the clinical
setting. In stifles with obvious instability, tib-
ial compression radiography is not required as
drawer motion will be detected on examination.
In palpably stable stifles affected by CR, the
presence of stifle effusion on radiographs and
orthopaedic examination are typically accurate
indicators of disease, especially when appro-
priate efforts to rule out other diseases (e.g.,
immune-mediated arthritis and osteochondri-
tis dissecans) have been performed. Thus,
tibial compression radiography is typically con-
sidered as a supplemental diagnostic test, rather
than a necessary one. Another limitation is
radiation exposure of the handler (ionizing
radiation regulations in certain countries may
preclude the use of this test). Modifications of
the technique where devices are used to induce
tibial compression have been suggested, but not
well described or validated.Stress devices
Several devices for conducting stress radiog-
raphy have been described. One such device
was developed with the aim of precisely quan-
tifying cranio-caudal tibial translation through
the controlled application of a cranially (or cau-
dally) directed force on the crus, while keep-
ing the thigh region stationary (Lopezet al.