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Treatment of Excessive Tibial

Plateau Angle

Michael P. Kowaleski

Introduction

The proximal tibial articular surface is angu-
lated distally with respect to the mechanical axis
of the tibia; the magnitude of this angulation is
termed the tibial plateau angle (TPA). The mean
TPA in dogs has been reported to range from
23.5◦to 28.3◦, with individual dogs having a
TPA as low as 12◦or as high as 46◦(Pacchiana
et al. 2003; Priddyet al. 2003; Reif & Probst 2003;
Moelleret al. 2006; Staufferet al. 2006). The mor-
phology of the proximal tibia in dogs with a
steep tibial plateau slope can be distinctly differ-
ent than normal dogs (Figures 30.1A and 30.2A)
(Osmondet al. 2006). Affected dogs may have a
steep TPA and/or a proximal tibial shaft defor-
mity in which the cranial border of the tibia
is angulated from caudal to cranial rather than
the more typical proximal to distal orientation
(Read & Robins 1982; Osmondet al. 2006).
Slocum^1 defined excessive tibial plateau
angle (eTPA) as a TPA greater than 34◦when
using a 24-mm radius tibial plateau leveling
osteotomy (TPLO) blade. However, this defini-
tion does not account for individual variation

(^1) Seminars entitled “Tibial Plateau Leveling Osteotomy
for Cranial Cruciate Ligament Repair,” Slocum Enter-
prises, Inc.
in proximal tibial anatomy. After the TPLO pro-
cedure, the tibial plateau segment acts as a but-
tress to support the tibial tuberosity (Talaatet al.
2006; Hamiltonet al. 2015). The point of inser-
tion of the patellar tendon on the tibial tuberos-
ity has been suggested as a safe point (maxi-
mum) for rotation (Figure 30.2A,B) to reduce
the risk of tibial tuberosity fracture (Talaatet al.
2006). This has been substantiated in a mechan-
ical study on the effect of osteotomy position
and tibial plateau rotation on the tensile force
required for failure of the canine quadriceps
mechanism (Hamiltonet al. 2015). Thisex vivo
study revealed that rotation of the tibial plateau
segment below the patellar tendon insertion
decreased the force required for tibial tuberos-
ity fracture, supporting the idea of a safe point,
with the tibial plateau providing buttress to the
tibial tuberosity (Hamiltonet al. 2015).
Preoperative planning
Preoperative planning can be used to deter-
mine the chord length corresponding to the
safe rotation distance. A tibial osteotomy guide
is centered on the point dividing the inter-
condylar tubercles, at the intersection of the
tibial mechanical axis and tibial plateau axis
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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