Advances in the Canine Cranial Cruciate Ligament, 2nd edition

292 Surgical Treatment

Considering the innervation of the entire stifle,
the receptors in the CrCL constitute only a small
minority. It seems, however, that the canine
CrCL has more mechanoreceptors than other
species. According to Arcandet al. (2000), more
than 450 receptors could be identified in the
canine CrCL compared to very few receptors in
humans (<20) (Hogervost & Brand 1998) and
cats (<50) (Madeyet al. 1997). The comparison
should be interpreted with caution due to dif-
ferent study designs and detection techniques.
It is, however, an interesting observation, as cats
and humans produce less severe osteoarthritis
after CrCL rupture compared to dogs. Free
nerve endings are mainly nociceptors, which
react to inflammation and pain stimuli (Cole
et al. 1996). Vasoactive neuropeptides, such
as substance P, have been reported in free
nerve endings and are thought to behave as
vasoactive substances. Free nerve endings do,
therefore, not only transfer information but
also have effector functions such as vasodila-
tion, vascular permeability, and effects on the
immune system (Hogervost & Brand 1998). In
considering this information, and the fact that
the CrCL helps to maintain joint stability and is
beneficial in preventing meniscal tears, it seems
that total debridement of the partially ruptured
CrCL should be used cautiously.
Since the introduction of arthroscopy, diag-
nosis and surgical treatment of cruciate liga-
ment rupture has been performed much earlier
during the disease process. Early detection of
anatomic partial ruptures of the CrCL has con-
sequently increased. This is documented by the
fact that before the introduction of arthroscopy
in CR treatment an incidence of 8% of partially
ruptured CrCL diagnosed during surgery was
reported during the 1990s (Scavelliet al. 1990)
compared to 21% in 2000 (Ralphs & Whitney
2002) and 41% observed during a period in
which arthroscopy has become a routine pro-
cedure (Gatineauet al. 2011). With this evo-
lution in mind, it has become very impor-
tant to assess the different possibilities of CrCL
debridement. Intraoperative decisions of how
much to debride can be very difficult. Accurate
visual grading of the percentage of torn CrCL is
difficult because ligament tissue that appears to
be intact may mask a substantial injury. Plastic
deformation is possible and leads to a lax non-
functional ligament. Electrothermal shrinkage
of collagen fibers of a lax ligament is potentially

possible, and has been used in the treatment of

lax ACLs in humans (Lamaret al. 2005). After

initial promising results, however, a multicen-

ter study showed a high failure rate for thermal

shrinkage, with the conclusion that this was not

an appropriate treatment (Smithet al. 2008).

Ligament debridement for complete

CrCL rupture

It is well known that ruptured cruciate liga-

ments do not heal spontaneously (Heftiet al.

1991), and mechanoreceptors probably do not

regenerate and have a questionable func-

tion without physiologic tension (Hogervost &

Brand 1998). Further, some believe that rem-

nants of the ligament might be an inflamma-

tory trigger and increase osteoarthritis. Experi-

mentally, it has been shown that CrCL remnants

disappear 3 months after CrCL transection

in rabbits (Heftiet al. 1991). In canine clini-

cal and experimental cases, resorption of the

torn ligament is also possible. However, in

contrast nodular, vascularized swellings (Fig-

ure 34.1A,B) or drumstick formations of the free

(A)

(B)

Figure 34.1 Macroscopic view of two canine stifle

joints after experimental cranial cruciate ligament (CrCL)

transection 12 months earlier. Note the marked cartilage

degeneration, meniscal damage and (A) CrCL resorption

versus (B) CrCL vascularized proliferation.