Does the Risk of Patella Fracture Increase with Decreasing Tibial Plateau ANGLE following Tibial Plateau Leveling Osteotomy?

Introduction: Patella fracture has been reported as a rare complication (0.09–2.0%) following tibial plateau levelling osteotomy (TPLO). Over-rotation of the tibial plateau angle (TPA) has been proposed as a possible cause. We hypothesized that the risk of postoperative patella fracture increases as TPA decreases following TPLO.

Materials and Methods: Medical records were reviewed for dogs with patellar fractures after a TPLO procedure. Relevant clinical and surgical data were recorded. Final radiographic TPA (fTPA), >6 months of postoperative or at time of fracture diagnosis, was blinded to outcome and measured using PACS software. The fracture and control groups were compared using the Wilcoxon rank-sum test. Statistical significance was set at 0.05.

Results: Patella fractures were identified in 20 stifles; 65 stifles were identified as a control population. Median follow-up time for the control group was 471 days (range 180–1868); median time to fracture diagnosis was 69 days (range 31–189). Median fTPA for the control group was 4.1° (range (-3.9)-14.1). Median fTPA for the fracture group was 1.4 degrees (range −10.3 to 7.1). Statistical analysis found a 21.7% (95% CI: 8.6–35.6%) increase in risk of patella fracture for every 1-degree decrease in TPA.

Discussion/Conclusion: In this study, the risk of patella fracture following TPLO increased as postoperative TPA decreased. Based on these findings, over-rotation of the tibial plateau during the TPLO procedure is a significant risk factor for patella fracture post-TPLO, and care should be taken to avoid over-rotation to decrease the likelihood of patella fracture following TPLO.