Understanding tibial plateau leveling osteotomies in dogs
You've heard a lot about TPLO and have possibly even referred patients for it, but you may still question exactly how it is performed and how it stabilizes the stifle. This surgeon walks you through the procedure so you'll be better equipped to educate your clients about its basis, some of its intricacies, and its potential complications.
Figure 2B. Templates corresponding to various sizes of TPLO saw blades can be superimposed on the mediolateral radiograph
to select the proper size of blade and to plan its orientation centered about the most proximal point of the tibial functional
axis (white arrow). The large dot at the intersection of the three lines (black arrow) indicates the proposed placement of
the most proximal jig pin as close to the most proximal point of the tibial functional axis as the anatomy will permit.
A recent geometric study of TPLOs emphasized the importance of surgical precision and suggested that extensive preoperative
planning from radiographs may improve the surgeon's intraoperative performance.13 The surgeon can use transparent templates to evaluate the suitability of the various sizes of TPLO saw blades, jigs, and
bone plates (Figures 2B & 2C). Because the position of the most proximal jig pin is critical, its desired position (immediately distal to the proximal
point of the tibial functional axis and several millimeters distal to the subchondral bone plate) is marked on the film (Figure 2B). Then a template for the selected saw blade size, centered about the most proximal point of the tibial functional axis,
is used to mark the desired position of the osteotomy on the film (Figure 2B).
Figure 2C. A transparent template corresponding to different sizes of TPLO plates is used to plan the position of the bone
plate and screws relative to the stifle joint and the proposed positions of the jig and the osteotomy.
Once the tibial plateau angle and appropriately sized saw blade have been determined, the amount of displacement needed along
the circumference to accomplish the desired postoperative tibial plateau angle is determined from the Slocum TPLO chart (Slocum
Stainless Steel TPLO Rotation Charts—Slocum Enterprises). A transparent template corresponding to different sizes of TPLO
plates can be made from radiographic film. This template is used to plan the position of the bone plate and screws relative
to the stifle joint and the proposed position of the jig and the osteotomy (Figure 2C)
A caudocranial radiograph is used to evaluate the alignment of the tibia and to identify palpable landmarks that can help
the surgeon avoid intra-articular placement of screws and jig pins. The stifle must be locked in full extension during caudocranial
stifle radiography so that minimal physiologic rotation is present within the stifle joint (Figure 3A).
Figure 3A. Patient positioning for a caudocranial radiograph of the stifle for TPLO planning. The patient is positioned with
the stifle fully extended. Abducting the opposite limb helps center the patella on the distal femur.