Radiographic assessment of popliteal sesamoid position and cranial tibial subluxation in canine stifle joints undergoing TPLO: A retrospective study of 163 dogs

Objective: To determine the prevalence of popliteal sesamoid displacement (PSD) in dogs with cranial cruciate ligament disease (CCLD) on radiographs, assess its reduction following tibial plateau leveling osteotomy (TPLO), and evaluate cranial tibial subluxation (CTS) pre- and postoperatively. Study design: Retrospective radiographic observational study. Sample population: A total of 163 client-owned dogs diagnosed with CCLD and treated with TPLO. Methods: Pre- and postoperative 90° flexion radiographs were reviewed to assess CTS, tibial plateau angle (TPA), stifle opening angle, PSD, and osteotomy localization. Statistical analyses evaluated associations between PSD, CTS, TPA, and osteotomy location. Results: A PSD was observed in 14.4% of cases preoperatively and was associated with significantly higher CTS. Popliteal sesamoid reduction was achieved in 100% of cases post-TPLO. The CTS persisted postoperatively in all dogs with preoperative subluxation (N = 82; 50.3%), though at significantly reduced levels. Osteotomy positioning did not significantly affect postoperative CTS. Postoperative TPA showed a weak negative correlation with residual CTS. Conclusion: A PSD is an infrequent finding, typically associated with more pronounced preoperative CTS. This displacement reliably resolves after TPLO when CTS was minimal. Although postoperative CTS was frequently observed, it was generally mild and not significantly affected by the osteotomy location. Clinical significance: The PSD occurs infrequently after CCLD but is associated with increased CTS. Popliteal sesamoid reduction was associated postoperatively with minimal CTS and appropriate TPA. Radiographic assessment of popliteal sesamoid reduction may provide an additional, objective parameter for detecting any residual cranio-caudal instability following TPLO.