The fibula contributes minimally to torsional stiffness and strength of the canine crus in an ex vivo study in Beagles.

The fibula contributes minimally to torsional stiffness and strength of the canine crus; tibial integrity is the primary determinant.

This ex vivo biomechanical study investigated the torsional mechanical properties of the canine crus and quantified the fibula's contribution to torsional stiffness and strength in skeletally mature Beagles. Thirteen pelvic limbs were divided into two groups: intact tibia-fibula constructs (n=7) and tibia with proximal fibular ostectomy (n=6). Specimens underwent quasi-static torsional loading to failure, with torque at failure, twist angle, torsional stiffness, and rotation relative to working length recorded. Mean torque to failure was 17.33 ± 2.95 Nm for intact crura and 18.45 ± 3.36 Nm following fibular ostectomy, with no statistically significant differences between groups for any measured variable. The isolated fibula sustained only 6.5% of the torque at failure of the intact crus. All specimens failed via mid-diaphyseal oblique or spiral tibial fracture, consistently preceding fibular failure. These findings confirm that torsional mechanical properties of the canine crus are predominantly determined by the tibia, with the fibula contributing minimally to torsional resistance. Clinically, this suggests that fibular integrity has limited influence on torsional stability in canine tibial fractures. However, the authors note that the fibula may still play an important role in maintaining limb alignment and guiding fracture management decisions. These data provide a biomechanical foundation for understanding tibial fracture mechanics and may inform surgical planning, particularly regarding the need for fibular repair or stabilization in dogs with tibial fractures.

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