Fracture Risk Evaluation of Trochlear Groove Depth in Toy and Small-Breed Dogs Under Gait-Based Loading: A Finite Element and Fatigue Analysis Study.

This study evaluated fracture risk associated with varying trochlear groove depth-to-patellar thickness (D/T) ratios in toy and small-breed dogs using finite element analysis and cadaveric mechanical testing. Finite element models derived from computed tomography data of a 4.5-kg toy poodle were adjusted to simulate D/T ratios ranging from 0.5 to 2.0 and analyzed for von Mises stress, principal strain, safety factor, and fatigue life under standing, trotting, and jumping conditions. Increasing D/T ratios led to progressive rises in stress and compressive strain, with the safety factor falling below 1.0 during jumping at ratios of 1.0 or higher. Fatigue life declined sharply beyond a ratio of 1.25 and reached zero-cycle failure at 2.0. Complementary mechanical testing of six distal femurs (6.42-8.7 kg), surgically modified to D/T ratios of 0.5, 1.0, or 1.5, revealed fracture patterns consistent with finite element predictions. These findings suggest that excessive trochlear deepening may compromise femoral integrity and elevate fracture risk, particularly under cyclic loading. Maintaining a D/T ratio between 0.75 and 1.0 may provide an optimal balance between effective patellar tracking and mechanical safety.