Tibial Plateau Leveling Osteotomy 219accuracy of osteotomy placement over the pre-
vious jig model (Burtonet al. 2013; Tanet al.
2014).
TPLO reportedly eliminates the wedge effect
of the medial meniscus, which may protect it
from postoperative injury (Pozziet al. 2006).
Hence, the necessity for medial meniscal release
during TPLO has been debated and appears to
be related to the quality of intraoperative menis-
cal evaluation. A subsequent meniscal tear is
3.8-fold more likely to occur when meniscal
evaluation is performed via an arthrotomy and
no meniscal release is performed, as compared
to either meniscal evaluation via an arthroscopy
with no release or meniscal evaluation via
arthrotomy with a release performed (Thieman
et al. 2006). Importantly, although TPLO elim-
inates dynamic craniocaudal stifle instability
and may impart protection to the medial menis-
cus, it fails to restore normal femorotibial con-
tact mechanics. Postoperative femorotibial con-
tact areas are significantly smaller than normal,
with higher peak contact pressures (Kimet al.
2009).
Patient selection
Appropriate case selection is important to the
success of TPLO. TPLO results in an increased
strain on the CaCLligament. Therefore, patients
with a compromised CaCL are not candidates
for the procedure (Warzeeet al. 2001). While this
surgery is most commonly performed on large-
breed dogs (Duerret al. 2014), patients as small
as a cat (Hoots & Petersen 2005) and as large as
a llama (Rayet al. 2004) have been successfully
treated with TPLO. Patient size in itself is not a
concern, as long as appropriately sized implants
are chosen for the procedure. With the contin-
ued introduction of smaller implants, TPLO is
quickly becoming more common in small-breed
dogs (Witte & Scott 2014; Cosenzaet al. 2015).
It is important to note that the morphology of
the proximal tibia differs between large- and
small-breed dogs, with small-breed dogs gen-
erally having a larger TPA (Vedrineet al. 2013;
Aertsenset al. 2015).
Anecdotally, TPLO has been advocated in
cases with a lack of cranial drawer where
partial CR is suspected as a means to decrease
the biomechanical strain on the CrCL and
theoretically protect it from further damage.
Research now supports this recommendation
with three studies. Hayneset al. (2015) showed
that decreasing the TPA will decrease strain in
the intact CrCL. Hulseet al. (2010) reported nor-
mal to near-normal intra-articular structures
on second-look arthroscopic examination of
stifles with stable partial CR treated with TPLO,
while joints with full ruptures showed a range
of pathologic changes. At long-term clinical
follow-up in a small case series, progression of
osteoarthritis appeared reduced with ongoing
preservation of passive stability (Bargeret al.
2016).TPLO implant selection
A wide range of orthopaedic implant manu-
facturers produce commercially available TPLO
implants in a growing variety of sizes. Both
locking and non-locking implants are avail-
able (Figures 27.2 and 27.3). A biomechanical
comparison between three different commer-
cial manufacturer’s TPLO plates has been per-
formed in an axially loaded gap model: Syn-
thes TPLO plate (Synthes Vet, West Chester, PA,
USA)/tibia constructs were found to be signif-
icantly stiffer than Slocum TPLO plate (Slocum
Enterprises, Inc., Eugene, OR, USA)/tibia con-
structs, which were found to be not significantly
different than Securos TPLO plate (Securos,
Fiskdale, MA, USA)/tibia constructs (Klocet al.
2009). Notably, the Synthes TPLO implant used
in the above study was a locking bone plate,
whereas the Slocum and Securos implants were
conventional (non-locking) bone plates.
The use of locking bone screws causes
significantly less translational movement of
the proximal tibial segment towards the bone
plate compared to the use of conventional bone
screws in an identical plate. However, no signif-
icant difference exists between locking and con-
ventional screw constructs in mean stiffness or
cycles to failure under load-sharing conditions
(Leitneret al. 2008). Mechanical testing between
non-locking and locking plates in an osteotomy
gap model showed that locking plates have a
higher load to failure, with the broad locking
plate having both a higher load to failure and a
greater mean stiffness (Bordelonet al. 2009). A
retrospective evaluation of change in TPA