206 Surgical Treatment
decellularization on deep digital flexor tendons
showed a significant decrease in DNA content,
preservation of the ECM, and no significant
change in mechanical properties.
The use of allografts has been described in
veterinary medicine (Shinoet al. 1984; Vasseur
et al. 1991), with studies examining ideal graft
size, mechanical strength, histology, and clin-
ical outcome (Qu et al. 2015). Vasseuret al.
1985 replaced the CrCL with CrCL allografts
in mixed-breed dogs in two studies. The first
study resulted in unstable stifles at 9 months,
with the allografts appearing immunogenic and
reaching only 14% of the strength of the intact
CrCL. A second study, although small and
short-term, demonstrated the possibility of a
successful outcome (Vasseuret al. 1987). Dogs
with stable stifles immediately after surgery
had a full recovery to normal gait (two dogs),
but when laxity was detected after surgery,
all dogs failed to have a successful outcome.
Thorsonet al. 1989 performed a similar study,
implanting CrCL allografts in 11 patients with
a 73% failure rate. Three dogs developed infec-
tions and were removed from the study, and
five of the remaining eight dogs had a limp at
4 months (Thorsonet al. 1989). Unfortunately,
there was no description of graft size or fixa-
tion strength. The above described study found
that allografts reached anywhere from 10% to
59% of the ultimate strength of an intact CrCL.
A more encouraging study included 28 dogs
which received CrCL allografts. Clinical assess-
ment of the dogs was not discussed, but allo-
grafts reached 90% ultimate strength of the nor-
mal CrCL at 36 weeks (Nikolaouet al. 1986).
Although the outcome measures were not clin-
ical, these authors concluded there were only
three failures during the 18-week study.
Freeze-dried fascia lata strips have also
served as allografts. In a study of medium-sized
dogs, eight patients underwent the ‘over-the-
top’ procedure, and eight dogs had graft place-
ment through bone tunnels. At 24 weeks, both
groups showed graft incorporation. Failure of
the grafts occurred at 536 N, compared to 801 N
for the intact CrCL (Curtiset al. 1985).
Other reported allografts for CrCL repair
have included the submucosa, bovine peri-
cardium, and the deep digital flexor tendon
(Figure 26.2) (Aikenet al. 1994; Biasiet al. 2005;
Brendolanet al. 2007; Biskupet al. 2017).
Figure 26.2 Intra-articular placement of a deep digital
flexor tendon allograft to replace the cranial cruciate
ligament in anex vivostifle.As allograft harvesting and preparation tech-
niques continue to develop, allografts may be
an inviting option for CrCLrepair. Further stud-
ies are required to determine initial strength, the
decrease in strength over time, cell ingrowth,
and immune reaction of any newly proposed
allograft.Prosthetics
Prosthetic ligaments have been described as
either a primary repair or as augmentation for
biological grafts (Knecht 1976; Kdolskyet al.
1997; de Roosteret al. 2001; Mascarenhas &
MacDonald 2008; Muller ̈ et al. 2010; Muller ̈
et al. 2011). Tissue-engineered scaffold bioma-
terials have been developed in attempts to
improve and accelerate healing or to recon-
struct tendons or ligaments altogether. They
avoid donor site morbidity, eliminate the risk