Advances in the Canine Cranial Cruciate Ligament, 2nd edition

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27


Tibial Plateau Leveling

Osteotomy

Susan L. Schaefer


Introduction


Tibial plateau leveling osteotomy (TPLO) was
first described in 1993 by Slocum to address sti-
fle instability due to cruciate ligament rupture
(CR) (Slocum & Slocum 1993). By decreasing
the natural caudodistal orientation of the tib-
ial plateau, TPLO limits the shear force gener-
ated by compression of the stifle during weight-
bearing, thereby abating cranial tibial thrust
(Reifet al. 2002). The dynamic stability imparted
to the cranial cruciate ligament (CrCL)-deficient
stifle via TPLO is achieved by performing a
radial osteotomy of the proximal tibia and rotat-
ing the proximal segment to decrease the tibial
plateau angle (TPA) (Figure 27.1).
Preoperative determination of the patient’s
TPA allows calculation of the magnitude of
rotation necessary to achieve a desired post-
operative TPA. The minimum amount of rota-
tion required to neutralize cranial tibial thrust
results in a postoperative TPA of 6.5±0.9◦.Fur-
ther rotation increases strain on the caudal cru-
ciate ligament (CaCL); rotating from 6.5◦to 0◦
increases CaCL strain by 37.7±17.4% (Warzee
et al. 2001). While convention dictates measur-
ing and changing the TPA, more recent studies
have evaluated the patella tendon angle (PTA)
change seen in TPLO. After TPLO, the PTA


measures around 90◦in bothex vivoand clinical
situations (Drygaset al. 2010; Sathyaet al. 2014).
This finding suggests that the biomechanics of
TPLO may be similar to that of tibial tuberos-
ity advancement (TTA). It is important to note
that the TPLO procedure itself only addresses
dynamic stifle instability. Therefore, an inspec-
tion of intra-articular structures with appro-
priate treatment of meniscal injuries or other
abnormalities must accompany the procedure.
An excellent review of the proposed mecha-
nism of action for TPLO is available (Boudrieau
2009).

TPLO technique


The magnitude of rotation planned preop-
eratively generally correlates well with the
realized postoperative TPA result (Windolfet al.
2008). However, achieving an accurate TPA
measurement and executing the osteotomy and
tibial rotation in a manner to accurately achieve
the desired postoperative TPA without inad-
vertently creating angular or rotational limb
deformities involves a complex interplay of fac-
tors. Intra- and interobserver variability in TPA
assessment has the potential to influence preop-
erative planning and subsequent postoperative

Advances in the Canine Cranial Cruciate Ligament, Second Edition. Edited by Peter Muir. © 2018 ACVS Foundation.
This Work is a co-publication between the American College of Veterinary Surgeons Foundation and Wiley-Blackwell.


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