Evaluation of femoral isometric placement accuracy of internal brace implants and its impact on stifle stability in the management of pivot shift phenomenon following TPLO.

Abstract

OBJECTIVE: To evaluate the impact of accurate isometric placement of internal brace implants on stifle stability following tibial plateau leveling osteotomy (TPLO) in dogs with pivot shift phenomenon and to propose a novel classification system for pivot shift grading. STUDY DESIGN: Retrospective observational study. ANIMALS: A total of 39 dogs (46 stifles) undergoing TPLO with internal brace augmentation using SwiveLock and FASTak implants. METHODS: Medical records, intraoperative assessments, and radiographs were reviewed. Femoral implant positioning was classified as accurate or inaccurate. Pivot shift was graded pre-, intraoperatively, and at 6-week follow-up using a simplified two-grade system. Learning curves for implant accuracy were compared between implant types. Statistical analyses included &#x3c7;and t-tests, with significance set at p&#x2009;<&#x2009;.05. RESULTS: Accurate implant positioning was achieved in 29 of 46 stifles (63.0%). SwiveLock implants were significantly more likely to be accurately placed than FASTak anchors (p&#x2009;=&#x2009;.016), with higher patient weight correlating with improved accuracy (p&#x2009;=&#x2009;.012). SwiveLock implants reached an accuracy rate of 78.6% compared to 38.9% for FASTak (p&#x2009;=&#x2009;.014). At follow-up, mean pivot shift grade improved in 90.9% of stifles (p&#x2009;<&#x2009;.001). Inaccurate implant positioning was significantly associated with increased internal tibial rotation (p&#x2009;=&#x2009;.009) but not with the pivot shift grade (p&#x2009;=&#x2009;.142). CONCLUSION: Accurate isometric placement of internal brace implants is critical for optimizing stifle stability and addressing pivot shift following TPLO. CLINICAL SIGNIFICANCE: Enhanced implant accuracy and a standardized pivot shift classification may improve surgical outcomes and guide postoperative management in dogs.