Tibial Tuberosity Advancement 235Figure 28.7 Lateral radiographs of the stifle joint, demonstrating the variation between the insertion points of the
patellar tendon into the tibial tuberosity. (A) Tibial tuberosity with a low insertion point. (B) Tibial tuberosity with a high
insertion point. A smaller plate must be applied when a shorter tibial tuberosity distance is available. The result is an
increase in the forces at each tine of the fork. Additionally, the overall plate length is shortened, potentially creating a
stress riser at the distal end of the osteotomy and the screws placed to secure the distal end of the plate. The tuberosity
shifts proximally with advancement in order to maintain patellar position. Furthermore, cage position (double-headed
arrow) provides greater buttress support of the tuberosity, and also buttresses the proximal attachment of the plate when a
high insertion point is present.
be determined. No data have been published
regarding the range of TPAs in dogs with TTA,
although it has been presented that successful
procedures have been performed in dogs with
aTPAof∼ 30 ◦. Anecdotally, it is proposed that
angles> 30 ◦are not well suited for a TTA (2007
Veterinary Symposium – The Surgical Summit;
Pre-Symposium Laboratories: TTA Laboratory;
Chicago, IL, USA).
Angular and torsional limb deformities
Angular and torsional limb deformities may
be treated with TTA. However, a separate
osteotomy is required for correction of any tib-
ial varus, valgus, or torsion. The disadvan-
tage of performing a separate osteotomy is
that the medial side of the bone already has
a plate positioned for the first-generation TTA
Figure 28.6 (Continued) spans the osteotomy gap 2–3 mm distal to the tibial plateau surface (white arrows). Note the
location of this cage and the corresponding location of the most proximal point of the tibial tuberosity. The width of the
cage is not equal to the distance observed in panel B; rather, it is wider as the upper edge of the cage and the
corresponding cage size is NOT placed at the level of the proximal point of the tibial tuberosity. (E) The appropriate plate
template is selected that spans the length of the tibial crest, and its orientation is noted so as to provide appropriate
positioning of both the fork and the distal screws of the plate. The large green arrowheads show the plate more caudally
positioned proximally as the most cranial border cannot be followed due to the concave cranial border of the tibial crest.
Note that the distal portion of the plate also overlies the tibial diaphysis, this occurs despite a slightly more caudal
orientation. (F) Postoperative radiograph that has copied the virtual plan and successfully resulted in appropriate
advancement to obtain a patellar tendon angle of 90◦. The osteotomy and its position, and the cage and plate positions
have been successfully duplicated on the patient.