Effect of Tibial Plateau Leveling Osteotomy on Patellar Tendon Angle: A Radiographic Cadaveric Study

Objectives: To determine the effect of tibial plateau leveling osteotomy (TPLO) on patellar tendon angle (PTA) in dogs. Study Design: Cadaveric radiographic study. Animals: Pelvic limb pairs (n=5) obtained from skeletally mature dogs, weighing 22–36 kg. Methods: TPLO was performed using a radiolucent jig that allowed for plateau segment rotation to a tibial plateau angle (TPA) of 15°, 6°, and 0°. Before, and at each of the prescribed rotations, PTA was measured by the tibial plateau (PTATP) and common tangent (PTACT) methods with the stifle positioned at 135° of flexion. Linear regression analysis was performed to evaluate the correlation between TPA and PTA. Results: At a mean (±SD) TPA of 5.9±0.7°, mean±SD PTATP and PTACT were 94.1±1.6° and 86.8±2.5°, respectively. A linear correlation was observed between TPA and PTATP (r=0.85) and between TPA and PTACT (r=0.61). Based on the regression equation of TPA and PTACT, a TPA of 12° corresponded to a PTACT of ∼90°. Conclusion: TPLO to a TPA of 6° reduces PTA to values similar to those recommended when performing tibial tuberosity advancement in dogs with cranial cruciate ligament insufficiency. Clinical Relevance: TPLO may neutralize tibial thrust by modifying PTA as well as decreasing TPA. TPLO to a TPA of 6° may not be necessary to neutralize the cranial tibial thrust according to the plateau rotation based on PTACT measurement.