Preoperative Tibial Plateau Leveling Osteotomy Planning Using the Conventional and Common Tangent Methods: A Cadaveric Study

Objective - To compare preoperative tibial plateau leveling osteotomy planning using the common tangent method to the current conventional method and evaluate the effect on tibial translation and patellar ligament angle following rotation of the tibial plateau.

Study Design – Cadaveric study. Seven paired canine pelvic limbs.

Methods- Radiographs of the stifle were taken at 135° of extension prior to and following rotation of the tibial plateau under load (0N and 30N). The tibial plateau of each limb was rotated both according to the common tangent and conventional method. Tibial plateau angle (TPA), tibial translation, and the patellar ligament angles (PLA) were measured radiographically following rotation of the tibial plateau.

Results- There was no significant difference between planning methods with regards to the amount of rotation of the tibial plateau or position of the tibia relative to the femur following rotation. There was no significant association between the postoperative tibial plateau angle and position of the tibia relative to the femur between groups. There was no significant difference between the patellar ligament angles following rotation based on the common tangent or conventional method preoperative TPLO planning.

Conclusion- Both the conventional and common tangent TPLO planning results in adequate proximal tibial rotation to achieve a PLA of approximately 90°, thereby counteracting the compressive shear forces during ambulation. The TPA for both groups following rotation had no significant impact on the amount of cranial or caudal tibial translation relative to the femur.