[A new exploration and consideration of Type A fracture of distal femur based on finite element biomechanical analysis].

Objective: To investigate the changes of internal fixation stress under different angles of interior fracture line and different screw placement modes in the case of A-type distal femoral fracture. Methods: A 24-year-old healthy male volunteer was recruited to collect the right femur data. CATIA V5R21 software produced a 10 mm fracture gap at the external side of the femur 6.5 cm proximal to the joint line and different angle fracture lines were generated on the internal of the femur at the same height. Based on the actual measured dimensions, the three-dimensional (3D) model of the locking plate and screw was reconstructed using CATIA V5R21 software, ignoring the screw surface threads and then the assembly of the internal fixation of the titanium plate, screws and femur was done. All models were meshed using Hypermesh 13.0 software. The assembled 3D model was input into ABAQUS 6.14 to generate a finite element model. Preliminary finite element biomechanical analysis was performed using the four medial fracture line angles and the stress distribution of the internal fixation under the three screw placement modes, and then the analysis was continued after the optimal screw placement method was re-determined. Results: Under an axial loading of 700 N, with the increase of the angle of the fracture line, the stress of the lateral internal fixation gradually increased, and the displacement of the proximal end of the fracture gradually increased. The sequential screw placement method was superior to the leaping screw placement method. The placement of the first screw at the proximal end of the fracture was critical to the distribution of the internal fixation stress. Conclusions: The operation plan of the type A of distal femoral fracture needs to be confirmed according to the internal and external fracture's condition. When the fracture line is at a excessive positive angle or a negative angle, a simple lateral fixation may not provide a stable fracture fixation so that other fixation methods are needed.目的： 探究股骨远端A型骨折外侧完全缺损时，内侧不同骨折线角度及不同螺钉置入方式下的内固定应力变化。 方法： 招募1名24岁健康男性志愿者，采集其右侧股骨数据，并应用Mimics17.0、3-matic Research 9.0、CATIA V5R21、Hypermesh 13.0、ABAQUS6.14等软件建立右侧股骨的完整模型。使用CATIA V5R21软件在距关节线近端6.5 cm的股骨外侧处产生一个10 mm的骨折间隙，于同一高度股骨内侧生成不同角度骨折线；根据实际测量尺寸，重建锁定板和螺钉的三维模型，忽略螺钉表面螺纹并完成内固定钛板、螺钉和股骨的装配。使用Hypermesh 13.0软件对所有模型进行网格划分。将组装的三维模型导入ABAQUS 6.14生成有限元模型。对四种不同的内侧骨折线角度及三种螺钉置入方式下内固定的应力分布进行初步有限元生物力学分析，此后重新确定最佳螺钉置入方式后继续分析。 结果： 在700 N的轴向加载下，随着骨折线角度的增大，外侧内固定的应力逐渐增大，骨折近端的位移逐步增大，且连续螺钉置入方式优于跳跃式螺钉置入方式，骨折近端第一枚螺钉的置入对内固定整体应力的分布至关重要。 结论： 需要根据内、外侧的骨折情况选择股骨远端A型骨折的手术方案，在骨折线为正角度但角度过大或骨折线为负角度时，单纯的外侧内固定可能不能有效稳定骨折，需要其他方式辅助固定。.