Biomechanical efficacy of a medial buttress plate in the management of concomitant ipsilateral subcapital and intertrochanteric femoral fractures: a finite element analysis

BACKGROUND: Although the incidence of ipsilateral femoral neck and intertrochanteric fractures (IFNIF) is relatively low, the postoperative complications associated with internal fixation surgery are relatively high. Recently, a medial support plate combined with proximal femoral plates (MPP) has been employed to manage this fracture type in our hospital, yielding favorable clinical outcomes. However, the lack of biomechanical evidence currently limits the validation of this approach. The objective of this study was to evaluate the biomechanical stability of MPP in the treatment of IFNIF using finite element analysis. METHOD: A finite element model was developed to simulate the fixation of IFNIF using medial support plate combined with proximal femoral plates (MPP) or individual proximal femoral plate (PP) fixation. The deformation, Von Mises stress distribution on the internal fixator, and equivalent elastic strain at the fracture site were analyzed and compared under three loading conditions: walking, stumbling, and lateral falling. RESULTS: Walking Condition: Under walking conditions, as the elastic modulus increased, deformation generally decreased in both the MPP and PP groups; however, the PP group exhibited consistently greater deformation values. Specifically, at an elastic modulus of 363.2 MPa, the deformation in the PP group was 68.249 mm, significantly higher than the 51.875 mm observed in the MPP group. The Von Mises stress in the PP group consistently exceeded that in the MPP group, with values of 721.65 MPa and 621.29 MPa, respectively, at 363.2 MPa, indicating that the PP group was more susceptible to fixation failure. Additionally, the equivalent elastic strain values in the PP group consistently surpassed those in the MPP group, reaching a maximum of 0.18771 compared to 0.1422 in the MPP group. Stumbling Condition: In the "Stumbling" condition, both groups exhibited a significant increase in deformation compared to the "Walking" condition, with the PP group demonstrating higher values, reaching 206.520 mm at 363.2 MPa. Von Mises stress levels increased substantially in both groups, with the PP group reaching 2183.70 MPa at 363.2 MPa. Equivalent elastic strains also increased markedly, with the PP group reaching a maximum of 0.56801, which was 34% higher than the MPP group's maximum of 0.42382. Lateral Falling Condition: In contrast, deformations in the "Lateral Falling" condition were notably lower. The MPP group exhibited a maximum Von Mises stress of 1699.3 MPa in the medial buttress plate and a femur stress of 253.20 MPa. Equivalent elastic strains in this condition were lower than those observed during "Stumbling", with the PP group's maximum value of 0.1418 slightly exceeding the MPP group's maximum of 0.13446. CONCLUSION: The MPP technique demonstrates enhanced biomechanical stability in this finite element model for the fixation of IFNIF, which could minimise the risk of migration and failure of internal fixation. These findings are hypothesis-generating and warrant further clinical validation.