Intra-Articular Repair for Cranial Cruciate Ligament Rupture in the Dog 209(A)(B)Figure 26.3 Lateral (A) and craniocaudal (B)
radiographs of a stifle at one year after placement of an
intra-articular deep digital flexor tendon allograft secured
with a cross-pin on the femur and spiked washer on the
tibia.
the synovial sheath is disrupted, the ligament
is exposed to synovial fluid, which contains
inflammatory mediators. The sheath contains
vessels that serve as an important blood sup-
ply to the ligament (Murrayet al. 2006). When
a graft is initially placed, it lacks the synovial
sheath, and this is suggested to deprive the
graft of an early blood supply and expose it to
inflammatory mediators (Arnoczky & Marshall
1981). The CrCL is exposed to constant mechan-
ical forces during weight-bearing, and it is dif-
ficult to protect the ligament with a brace or
internal repair. In a CrCL model, the ends of a
transected CrCL were sutured into apposition,
and the stifle was immobilized. At 10 weeks,
the CrCL had shown evidence of healing but
did not reach full strength (O’Donoghueet al.
1966). Lastly, an appropriate scaffold is nec-
essary for cell migration. In one study, a 3.5-
mm defect was created in the CrCL, leaving
peripheral bands to provide stability (Spindler
et al. 2006). The defect failed to show signifi-
cant healing over a 6-week period. The addi-
tion of a collagen–platelet-rich plasma scaffold
promoted healing over the same time period
(Murrayet al. 2006; Silvaet al. 2013). These stud-
ies demonstrate the importance, for any graft,
of a suitable scaffold for cell migration and the
necessity to mechanically protect the graft dur-
ing healing.
Autografts and allografts provide a natu-
ral ECM to guide cell ingrowth and, if pro-
cessed appropriately, can initially maintain a
similar mechanical strength. All grafts will lose
strength over time if replacement with appro-
priate native tissue does not proceed rapidly.
One possible stimulant is the proteins in the
ECM of a donor autograft or allograft (Hogan-
sonet al. 2010). Although prosthetic implant
scaffold technology is improving, the three-
dimensional layout of the scaffold likely can-
not perfectly mimic Nature. It is unknown how
a different matrix affects cell ingrowth. Both
natural and synthetic scaffolds can be seeded
with protein, or potentially cells, to promote
ingrowth (Linonet al. 2014).
Many surgeons believe that intra-articular
grafts historically failed due to biological break-
down, similar to the fate of the native CrCL.
The exact pathogenesis of CR is not known
(Comerfordet al. 2011) and, therefore, there is
no definitive evidence that an implanted graft