Objective: To investigate how tibial long axis (TLA) shift affects the postoperative tibial plateau angle (TPA) in four cranial closing wedge ostectomy (CCWO) techniques.
Study design: In silico study.
Sample population: A total of 15 client-owned dogs.
Methods: Computed tomography (CT) scans of 15 client-owned dogs were reviewed using an open-source 3D computer graphics editor. Each computer-generated 3D tibia model underwent a CCWO, with cranial cortex alignment, in 10° increments up to 70° using each of the four previously described techniques. The TLA shift, TPA and mechanical tibial length (mTL) were calculated, using trigonometry, for each model. Equations for predicting final TPA were generated with linear regression.
Results: A total of 433 3D computer generated tibial models were analyzed. With each technique, the TPA varied in a linear fashion within the studied range of wedge angles. The TLA shift and tibial shortening magnitude varied between the four different CCWO techniques, with maximum mTL reduction of ranging from 7.5% to 40.9%. All predicted TPAs using the generated equations were within the target range of 4-6°.
Conclusion: A linear relationship between ostectomy wedge angle and TPA correction was observed in this study, which allowed for generation of accurate corrective equations.
Clinical significance: These results allow extrapolation of the wedge angle required to reach a postoperative TPA of 5°, by considering the TLA shift. The use of the generated corrective equations may thus increase CCWO planning precision.