Intra-Articular Repair for Cranial Cruciate Ligament Rupture in the Dog 203Barr 1998). With the development of extra-
articular sutures and tibial osteotomies, intra-
articular repairs fell out of favor due to their
inferior outcomes, continued stifle instability,
progressive cartilage degeneration, and donor
site morbidity (Butleret al. 1983; Elkinset al.
1991; Inneset al. 2000a; Johnsonet al. 2001; Innes
et al. 2004; Conzemiuset al. 2005; Snowet al.
2010; Molsaet al. 2014). These studies, as well
as surgeons’ own experiences with the proce-
dure, have led to intra-articular repairs being
mostly abandoned in North America. How-
ever, a review of the literature addressing intra-
articular repair in dogs identifies three common
limitations: inappropriate graft selection; inap-
propriate fixation; and an inappropriate biolog-
ical environment for graft healing.
Graft selection
Autografts
The autograft is a natural extracellular matrix
(ECM) scaffold that initially can provide biome-
chanical properties similar to the native liga-
ment, as well as a biochemical and structural
composition to guide cell growth. In addition,
growth factors may be trapped within the natu-
ral ECM, providing a source of biological stim-
uli that promote ligament fibroblast differen-
tiation. Autografts also minimize the risk of
immune detection and disease transmission.
The use of autografts was described in many
original techniques and continues to be one
of the most commonly used grafts in humans
(Murray 2009). In veterinary medicine, using a
portion of the straight patella tendon or a strip
of the fascia lata is most commonly reported,
although skin, peroneus longus, flexor digi-
talis pedis longus, long digital extensor, perios-
teum and semitendinosus/gracilis autografts
have all been described (Chiroff 1975; Knecht
1976; Arnoczkyet al. 1979a; Ramanaiahet al.
1990; Inneset al. 2000a; Lopezet al. 2003; Veena
et al. 2003; Penhaet al. 2007).
Patella tendon autograft use, a technique
modified from human medicine, allows for
either bone or soft tissue anchor points,
and was first described by Dueland in 1966
(Dueland 1966). Dueland harvested the central
third of the straight patella tendon and patella,
creating a tendon-bone graft. The distal end
of the graft maintained attachment to the
tibia, while the free proximal end was passed
through a femoral tunnel and sutured to the
gastrocnemius. Although Dueland felt the
outcomes were good, very few were reported.
Subjective outcomes were promising enough
that the procedure and its modifications were
performed by Dueland until his retirement.
A modification was described in 1979, where
the lateral third of the straight patella tendon,
as well as a strip of fascia lata, was passed
through the joint and over the caudal aspect
of the lateral condyle, often referred to as the
‘over-the-top’ technique (Arnoczkyet al. 1979a;
Arnoczky et al. 1979b; Denny & Barr 1984;
Bennett & May 1991).
Although intra-articular autografts have been
described for over 50 years, there is a paucity
of information on the suitability of these
grafts, specifically their ability to heal, graft
mechanical strength, graft attachment mechani-
cal strength and donor site morbidity. Objective
outcomes were evaluated in 1975, when heal-
ing was assessed in experimentally replaced
CrCL using a third of the patella tendon
(Chiroff 1975). Both the tendon and bone under-
went necrosis before more rapid ingrowth
occurred. Although healing progressed quickly
initially, incorporation remained incomplete at
one year. The modified ‘over-the-top’ technique
showed there was graft revascularization where
the graft contacted the fat pad and caudal joint
soft tissues, suggesting vessel ingrowth into
the sides of the graft rather than longitudi-
nal revascularization (Arnoczkyet al. 1979b;
Arnoczkyet al. 1982). In contrast, a small pilot
study showed that at one year, a hamstring
graft had histopathology similar to the normal
CrCL. Clinically, it was reported the patients
were not showing signs of lameness (Lopezet al.
2003). Subsequent studies have revealed simi-
lar results of incomplete and inconsistent revas-
cularization and repopulation based on graft
selection (Baconet al. 1984; McFarlandet al.
1986; Nget al. 1995; Fuet al. 1999).
Available data showing the initialin vitroand
in vivomechanical strength of common auto-
grafts is minimal. Given the critical role that
the CrCL plays in stifle mechanics, it is believed
to be of paramount importance to demonstrate
that a surgical technique can reproduce the
salient mechanical features of the intact CrCL.
Tensile testing of the medial third, central third