Background To compare the biomechanical parameters of AO/OTA type A3 distal femoral fractures fixed bilaterally with an ortho-bridge system (OBS) and lateral locking compression plate + locking reconstruction plate (LCP + LRP). Methods Twelve A3 distal femoral fracture models with medial cortical defects of the distal femur were created using synthetic femoral Sawbones. OBS and LCP + LRP were used for bilateral fixation, with six in each group. Axial compression and torsion tests were performed on the two groups of fracture models to determine their stiffness during axial compression and the torsion angles during torsion tests. Axial compression failure tests were performed to collect the vertical loads of the ultimate failure tests. Results In the test conducted on the fixed type A3 distal femoral fracture models, the axial stiffness in the OBS group (group A) (1072.61 ± 113.5 N) was not significantly different from that of the LCP + LRP group (group B) (1184.13 ± 110.24 N) (t = 1.726, P = 0.115), the torsion angle in the group B (2.6° ± 0.03°) was higher than that in group A (2.36° ± 0.1°) (t = 5.746, P < 0.001), and the ultimate failure test of type A3 fracture model showed that the vertical load to destroy group A fixation (5290.45 ± 109.63 N) was higher than that of the group B (3978.43 ± 17.1 N) (t = 23.28, P < 0.05). Notably, intertrochanteric fractures occurred in the A and B groups. Conclusions In the fixation of type A3 distal femoral fractures, the anti-axial compression of OBS was similar to that of the LCP + LRP group, but the anti-torsion was better.