Biomechanical advantages of double-column bridging plate-augmented PFNA for complex subtrochanteric femoral fractures: a finite element analysis.

backgroundFor complex subtrochanteric femoral fractures with lateral wall involvement, PFNA augmented with a lateral plate is commonly used; however, conventional reconstruction plates have limitations including poor anatomical conformity and insufficient anti-rotational capability. Whether a novel double-column bridging plate combined with PFNA can provide superior biomechanical performance under both normal and osteoporotic bone conditions requires validation.

methodsCT data of the left femur from one healthy adult volunteer were collected. Mimics 19.0, Geomagic Wrap 2017, and Creo 6.0 software were used to construct a Seinsheimer Type IV subtrochanteric femoral fracture finite element model along with PFNA, conventional reconstruction plate, and double-column bridging plate internal fixation device models. The study subjects were divided into three groups: Model A (PFNA alone), Model B (PFNA + conventional reconstruction plate), and Model C (PFNA + double-column bridging plate). Each model was further subdivided into a healthy bone subgroup and an osteoporotic bone subgroup, in which the elastic modulus of bone elements was uniformly reduced to 60% of the healthy value. Hypermesh 2014 software was used for mesh generation, and Abaqus 6.14 software was used to complete material property assignment, loading, and boundary condition settings before performing finite element simulation calculations. Maximum displacement, maximum torsional angle, maximum stress of internal fixation and fracture fragments were compared among the three models, and interfragmentary motion (IFM) visualization analysis was used to evaluate fracture site stability.

resultsUnder healthy bone conditions, Model C achieved the lowest maximum displacement (4.06 mm), torsional angle (2.15°), and intramedullary nail stress (344.6 MPa), representing reductions of 19.8% and 36.7% compared with Model A. The double-column bridging plate carried a higher stress (442.5 MPa vs. 254.5 MPa for the conventional plate), reflecting more active load sharing. At Contact Surface 2, Model C achieved a mean IFM distance of only 0.021 mm, markedly lower than Model A (0.139 mm) and Model B (0.103 mm). Under osteoporotic conditions, all models showed increased displacement and nail stress alongside decreased bone fragment stress, yet Model C consistently maintained superior performance, with the lowest nail stress (407.9 MPa, 26.8% reduction vs. Model A) and the smallest mean IFM distance at Contact Surface 2 (0.012 mm vs. 0.167 mm and 0.138 mm for Models A and B).

conclusionThis finite element analysis suggests that PFNA combined with the double-column bridging plate may offer biomechanical advantages over PFNA alone or PFNA with conventional reconstruction plate fixation in Seinsheimer Type IV subtrochanteric femoral fractures, with these computational advantages largely preserved under simulated osteoporotic conditions. The findings should be regarded as hypothesis-generating and require validation through in vitro biomechanical and clinical studies.