Seminar: Managing Excessive TPA: Strategies and Controversies
eTPA – An Isolated Angular Limb Deformity of the Proximal Tibia: A Combined Approach with TPLO/CWO Managing Excessive TPA: Strategies and Controversies
Professor of Clinical Sciences Emeritus Tufts University Cummings School of Veterinary Medicine Sherborn, Massachusetts
Dogs with excessive tibial plateau slope (eTPA) have been defined as >34°, although angles much greater do occur. Not only do these higher angles become problematic when performing a TPLO (isolating the tibial tuberosity above the level of the tibial plateau, thus predisposing to fracture), but also results in an angular deformity in the sagittal plane. This deformity results in a crouched limb stance in full extension of the stifle joint. In addition, these excessive angles of eTPA are frequently associated with other deformities of the proximal tibia, including varus, valgus and rotation. As such, a combined approach addressing both the eTPA and the other proximal tibial deformities can be successfully addressed with a combination of corrective osteotomies not only in the sagittal plane (TPLO/CCWO, which we routinely use to address eTPA) but also the deformities in the frontal plane by also combining a MCWO or LCWO within the same procedure to address proximal tibial varus or valgus. Addressing eTPA with a TPLO/CCWO requires a co-planar osteotomy that is performed in the sagittal plane, whereas a proximal tibial varus or valgus is addressed with a bi-planar osteotomy, with the orientation of the second portion of the osteotomy to be performed within the frontal plane. In addition, any rotational correction can easily be performed (provided the distal osteotomy if perpendicular to the long axis of the tibia). Furthermore, as some of these cases also involve patellar luxation, the tibial tuberosity segment may also be transposed as needed prior to final fixation (and also addressing any distal femoral malalignment as a separate procedure). Fixation is identical to a TPLO/CCWO to address the “simple” eTPA alone. As such, I find this “double-cut” TPLO procedure quite useful to be able to address the multitude of variations than can occur with his angular limb deformity.