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 degrees, 6 degrees, and 0 degrees. Before, and at each of the prescribed rotations, PTA was measured by the tibial plateau (PTA(TP)) and common tangent (PTA(CT)) methods with the stifle positioned at 135 degrees 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 degrees, mean+/-SD PTA(TP) and PTA(CT) were 94.1+/-1.6 degrees and 86.8+/-2.5 degrees, respectively. A linear correlation was observed between TPA and PTA(TP) (r=0.85) and between TPA and PTA(CT) (r=0.61). Based on the regression equation of TPA and PTA(CT), a TPA of 12 degrees corresponded to a PTA(CT) of approximately 90 degrees.

Conclusion: TPLO to a TPA of 6 degrees 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 degrees may not be necessary to neutralize the cranial tibial thrust according to the plateau rotation based on PTA(CT) measurement.