248 Surgical Treatment
feature such as steep slope (Read & Robins
1982) or small-sized patients (Maciaset al.2002).
Outcome after CCWO is similar to that after
TPLO (Corr & Brown 2007; Oxleyet al.2013). In
the Corr & Brown study the complication rates
were not different, but implant failure requiring
revision was seen more frequently with CCWO
treatment, although only a single TPLO plate
with standard screws was used for stabiliza-
tion. Complication rates, including late menis-
cal tears and wound and joint infections, were
similar between procedures in the study con-
ducted by Oxleyet al. (TPLO 7.2%; CCWO
9.5%). The CCWO technique involved plan-
ning a wedge that was more proximally posi-
tioned, had equal length osteotomy surfaces,
and was caudally hinged. The wedge size was
adjusted for the anticipated cranial axis shift,
with a larger adjustment made for larger correc-
tion angles. A pre-contoured TPLO plate with
all proximal screws locked and a supporting
cranial wire was used for all CCWO cases, and
no implant failures were identified. A review of
300 CCWO surgeries found an overall compli-
cation rate of 31.7% (Kuanet al.2009). Four dogs
(1.3%) required additional surgery to address
implant failure and osteotomy instability. The
type of plate and screws was not described, but
a cranially placed wire was used.
Conclusions
CCWO is an effective approach for leveling
the tibial plateau. Planning of the wedge size
must take into account the shift in the func-
tional axis that occurs as the ostectomy is closed.
This shift can be minimized by locating the
osteotomy more proximally and by aligning the
cranial fragment edges. Adequate fixation must
be used to counter the strong forces that act on
the osteotomy. A cranial ‘tension band’ of some
form is recommended to minimize the risk of
failure of fixation.
Triple tibial osteotomy
Introduction
Triple tibial osteotomy (TTO) was first
described by Bruceet al. in 2007. While the
goal is similar to that of the TTA, namely to
create a 90◦ angle between the tibial plateau
slope and the patella tendon at a stifle angle
of 135◦, this is achieved by a combination of a
closing wedge ostectomy (leveling of the tibial
plateau) and advancement of the tibial tuberos-
ity which is pushed by the cranio-proximal
corner of the rotating proximal fragment. In the
initial report a geometric analysis suggested
that if the wedge were two-thirds of the cor-
rection angle, the other one-third would be
achieved by the tuberosity advancement. A ret-
rospective analysis of the amount of correction
achieved indicated that this was insufficient,
and the formula was later revised to: Wedge
angle=Correction angle×0.6 + 7 (TTO Tech-
nique Guide, Veterinary Instrumentation, Inc.,
Sheffield, UK). This adjustment is likely due
to the shift in the functional tibial axis, and
the fact that the tuberosity advances cranially
only and not proximally, necessitating a larger
correction.Technique: planning
Planning is performed on a lateral radiograph
of the stifle at an angle of 135◦. The length of
the patella tendon is determined and the tib-
ial plateau–patella tendon (TP-PT) angle mea-
sured. The correction angle is the TP–PT angle
minus 90◦, and the wedge angle is calculated
using the formula given above.
The wedge angle may need to be adjusted in
dogs with unusual tibial tuberosity morphol-
ogy (Renwicket al.2009). If the patella ten-
don insertion is very low, the correction may
be overestimated, and if it is very high it may
be underestimated. Also, if the tibia is cranially
subluxated, or the stifle is more flexed than rec-
ommended when the radiograph is taken, the
measured correction angle will be less. It is rec-
ommended that radiographs be critically eval-
uated for position, the TPA be measured, and
the tuberosity morphology considered before
deciding on a final wedge angle.Technique: intraoperative
Specialized instrumentation is available that
simplifies a number of the steps in this
procedure (Veterinary Instrumentation, Inc.,
Sheffield, UK). First, the medial aspect of the