Optimal configuration of a three-rod ortho-bridge system in the treatment of Vancouver type B1 periprosthetic femoral fractures: A finite element analysis.

Introduction and Aim: Periprosthetic femoral fractures (PFF) represent an increasing clinical and economic burden. This study aims to determine the optimal configuration of a bridge-combined internal fixation system in the treatment of Vancouver type B1 PFF, using finite element analysis.

Materials and methods: A three-rod ortho-bridge system (OBS) fixation model was used to evaluate the optimal configuration of four target parameters: position of the third rod; intersection angle between the proximal screws; connecting rod diameter; and number of screws used. Femoral displacement and the maximum von Mises stress of the OBS were used as the evaluation indices, to analyze the PFF and to determine the optimal use of an OBS. For each parameter, various candidate options were tested.

Results: Finite element analysis revealed that the rate of femoral displacement and the maximum von Mises stress of the OBS were at a minimum when there was a 35 mm downward movement of the third rod from the baseline. Therefore, the optimal position of third rod fixation was 35 mm below the fovea capitis of the femur. The optimal intersection angles between the proximal screws were found to be 71.92° or 84°. A 6 mm diameter connecting rod proved to be most effective. Configuration d, utilizing 7 screws, represented the most clinically appropriate screw number configuration, despite configuration f, utilizing 9 screws, eliciting the best evaluation indices.

Conclusion: An OBS used in the above-described configuration is well suited to the characteristics of PFF and provides an effective and reliable means for their treatment.