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.
Figure1. Patient positioning for a mediolateral radiograph of the stifle for TPLO planning. The dog is placed in lateral
recumbency with the affected limb down. The stifle and hock are flexed to about 90 degrees. Note that the lateral surface
of the hip, stifle, and hock are placed on the same level and are in contact with the radiographic cassette. The radiographic
beam is centered on the stifle but includes the stifle and hock. The opposite limb is pulled cranially.
Precise patient positioning is required when obtaining radiographs in preparation for a TPLO.12 These radiographs are often obtained immediately before a TPLO because general anesthesia facilitates such precise patient
positioning. The tibial plateau angle is measured on a mediolateral radiograph centered on the stifle joint but collimated
to include the tarsus. If the stifle shifts away from the center of the radiographic beam, the tibial plateau angle will be
measured incorrectly.12 For a true lateral radiograph of the stifle joint, the tibia must be parallel to the radiographic film (Figure 1).
Figure 2A. A mediolateral radiograph showing the superimposition of the femoral condyles and the approximately 90 degrees
of flexion in both the stifle and the tarsus. Note the lines demarcating the tibial plateau slope (TPS), tibial functional
axis, and tibial plateau angle (TPA).
Radiographs obtained with the dog properly positioned display superimposition of the medial and lateral femoral condyles and
a distinct medial tibial plateau, though this may be difficult to achieve in patients with marked femoral varus, valgus, or
torsional deformity. The tibial plateau slope is defined by a line joining points at the cranial-most and caudal-most edges
of the medial tibial condyle (Figure 2A). The tibial functional axis is defined by a line joining the midpoint between the intercondylar tibial tubercles (in the
stifle joint) with the center of the talocrural joint. Next, a line is drawn perpendicular to the tibial functional axis.
The tibial plateau angle is defined as the angle formed between the perpendicular line and the tibial plateau slope.