Effects of proximal femoral fixation method and joint angulation on simulated muscle forces in a canine limb press model

Objective To quantify how increasing axial loads, femoral fixation methods (rigid vs. flexion‐extension mobility) and joint angles reflecting early versus mid‐stance impact simulated quadriceps and gastrocnemius forces. Study design Non‐randomized, cadaveric experimental study. Sample population Unpaired canine pelvic limbs ( n = 10) from adult large‐breed dogs. Methods Limbs were mounted in a custom limb press with the femur sequentially rigidly fixed at 70° to horizontal or allowed flexion‐extension. Quadriceps and gastrocnemius muscles were simulated with load cells and turnbuckles. Axial loads of 10%, 20% and 30% bodyweight (BW) were applied. Stifle and hock angles were sequentially fixed to represent mid‐ (135° and 145°) or early stance (145° and 135°). Outcome measures were BW normalized simulated muscle loads and their ratio. Data were analyzed using non‐parametric repeated measures. Results Quadriceps and gastrocnemius forces increased with axial load ( p < .001). Quadriceps force was unaffected by fixation method but showed higher mid‐stance values in flexion‐extension models at 20% and 30% loads ( p = .03). Gastrocnemius force varied by configuration ( p = .01) and showed significant load–configuration interactions ( p = .003); mid‐stance values were lower than early stance in flexion‐extension models. Muscle force ratios were consistent across loads ( p = .2) but differed by configuration ( p = .02), with higher mid‐stance values in flexion‐extension models. Conclusion Femoral fixation method and stance configuration had limited impact on simulated muscle forces. Flexion‐extension mobility did not substantially increase muscle loading. Impact Rigid femoral fixation remains a valid approach for canine limb press models.