Effect of Plate Inclination and Osteotomy Positioning on Rock-back following Tibial Plateau Levelling Osteotomy in Dogs.

Abstract

Objective:  Rock-back is a reported complication following tibial plateau levelling osteotomy (TPLO), whereby tibial plateau angle (TPA) increases postoperatively. The mechanism of rock-back is not fully understood, although a recent ex vivo investigation demonstrated that osteotomy exit cut angle (ECA) and inclination of the plate in the sagittal plane might be risk factors. The purpose of this study was to explore these relationships in a clinical dog population. We hypothesized that dogs with rock-back would have a higher degree of plate inclination and downward ECA compared with those without rock-back.

Materials and methods:  Medical records and radiographs of dogs that underwent TPLO between January 2021 and January 2022 were retrospectively reviewed. TPA was recorded preoperatively, postoperatively, and at follow-up. Plate inclination, ECA, and descriptive data were collected. Observers measuring TPA were blinded to other variables. Rock-back was defined as a change in TPA ≥ 2.

Results:  Ninety-five TPLO procedures met the inclusion criteria (n = 87 dogs). Rock-back was identified in 21% of TPLOs (n = 20/95). The mean increase in TPA in the rock-back group was 3.2 ± 2.6. Plate inclination and ECA were not correlated with the presence of rock-back. Descriptive variables did not have a significant correlation with rock-back.

Conclusion:  Plate inclination and ECA did not have a relationship with rock-back when defined as a postoperative TPA change ≥2 degrees, in this clinical retrospective study.