空心螺钉联合“8”、“0”张力带钢丝内固定治疗髌骨横行骨折模型的有限元分析与比较

目的 通过有限元分析(Finite Element Analysis，FEA)比较空心螺钉联合“8”或“0”张力带钢丝内固定系统治疗髌骨横行骨折模型的稳定性。 方法 采集1名48岁健康男性志愿者的计算机断层扫描(CT)图像。首先在计算机辅助设计(Computer Aided Design, CAD)系统中建立髌骨几何模型，导入到Ansys系统中，建立不含软组织和软骨的髌骨有限元模型。髌骨横切面与髌骨正中横切面相交，构建髌骨横行骨折模型。固定髌骨近端，在髌骨远端施加牵引力。模型设置在非负重伸展时膝关节屈曲90°的条件下，髌骨关节面中部与软骨覆盖的股骨远端接触。 结果 在牵引力200 N条件下，采用“8”或“0”张拉带钢丝固定系统固定时，螺钉的最大相对位移分别为0.32 mm和0.20 mm，钢丝的最大相对位移分别为0.36 mm和0.21 mm，髌骨的最大相对位移分别为0.35 mm和0.22 mm。两组螺钉的最大等效应力分别为778.01 Mpa和941.88 Mpa，钢丝的最大等效应力分别为311.51 Mpa和336.24 Mpa，髌骨的最大等效应力分别为3.81 Mpa和3.66 Mpa。两组螺钉和钢丝均存在应力集中。 结论 基于有限元分析，“0”张力带钢丝比“8”固定系统联合空心螺钉治疗髌骨横断骨折时更稳定。

Finite element analysis and comparison of the models of patellar transverse fracture fixed with hollow screw combined with “8” and “0” tension band wire internal fixation

Objective To compare the stability of patellar transverse fracture model fixed by hollow screw combined with “8” and “0” tension band wire fixation systems by finite element analysis (FEA). Methods Computerized tomography (CT) images were acquired from a 48-year-old healthy male volunteer. A geometric model of patella was firstly built in the computer-aided design (CAD) system, and then imported into the Ansys system. The finite element model of patellar was built without the soft tissue and cartilage. Patellar transverse fracture model was created by intersecting the patella on the median transverse section. The proximal end of the patella was fixed and tractive force was loaded on the distal end of the patella. The models were set in the condition of 90° knee flexion during non-weight-bearing extension with the middle part of the patellar articular surface contacting to a cartilage-covered distal femur. Results When the patella transverse fracture was fixed with “8” or “0” tension band wire fixation system, under distraction force of 200 N, the maximum relative displacement of screws were 0.32 mm and 0.20 mm, that of wires were 0.36 mm and 0.21mm and that of patella were 0.35 mm and 0.22 mm, respectively. The maximum equivalent stress of screws were 778.01 Mpa and 941.88 Mpa, that of wires were 311.51 Mpa and 336.24 Mpa, and that of patella was 3.81 Mpa and 3.66 MPa, respectively. Stress concentration was observed in screws and wires in both groups. Conclusions When combined with hollow screw in the treatment of patellar transverse fracture, the “0” tension band wire fixation system is more stable than the “8” fixation system based on FEA.