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 χ² and t-tests, with significance set at p < .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 = .016), with higher patient weight correlating with improved accuracy (p = .012). SwiveLock implants reached an accuracy rate of 78.6% compared to 38.9% for FASTak (p = .014). At follow-up, mean pivot shift grade improved in 90.9% of stifles (p < .001). Inaccurate implant positioning was significantly associated with increased internal tibial rotation (p = .009) but not with the pivot shift grade (p = .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.