3D打印踝关节融合假体重建胫骨远端肿瘤切除后骨缺损的有限元分析

3D-printed arthrodesis endoprosthesis for reconstruction of distal tibia after resection of tumor-A finite element analysis

目的通过对胫骨下段缺损假体重建后的模型进行有限元分析,了解假体重建模型各个部位的应力、形变,明确结构的初期强度,为临床应用提供理论依据。方法采集1名正常成年人胫腓骨薄层CT数据,采用Mimics软件进行胫腓骨及踝关节三维重建。通过Solidwork软件构建正常胫骨-腓骨-距骨模型与假体重建胫骨远端骨缺损模型。通过ANSYS软件应用有限元法进行力学分析。螺钉与假体的接触关系为绑定接触,假体与皮质骨的接触关系为滑移接触,螺钉与皮质骨的接触关系为绑定接触。在胫骨平台上施加600 N的垂直模拟载荷,以模拟人体单足站立时胫腓骨的状态,来评估和比较不同重建模型的应力和位移变化。在胫骨平台上的中立位施加600 N的垂直载荷,同时,再以胫骨的纵轴为旋转中心,施加2.7 N·m的顺时针和逆时针力矩,以模拟下肢的外旋载荷和内旋载荷。结果在施加600 N垂直应力于胫骨平台时,正常胫腓骨模型的最大von Mises压应力为8.27 MPa,von Mises压应力的集中区域为胫骨中段后方皮质骨。模型最大形变部位在胫骨平台外侧及腓骨头,形变距离为4 mm。施加2.7 N·m的顺时针和逆时针力矩时,最大von Mises压应力为14.25 MPa,位于胫骨中段皮质,位移最大点位于胫骨近端前方皮质,为2.47 mm。在模拟单腿站立时,假体模型的最大von Mises压应力为51.98 MPa,位于假体远端的1枚交叉螺钉处,模型的其余部分受力均匀。形变分析结果显示假体重建模型最大位移小于正常胫腓骨模型,仅为0.74 mm,位于胫骨平台外侧及腓骨头,部位与正常胫腓骨模型一致。施加2.7 N·m的顺时针和逆时针力矩,最大von Mises压应力为15.44 MPa,位于假体远端的抗旋转螺钉处,旋转时位移最大点位于胫骨平台外侧与腓骨头接触部位,仅为0.07 mm。结论胫骨下段3D打印踝关节融合型假体重建胫骨下段恶性骨肿瘤切除后的骨缺损模型中假体及骨受力均匀,稳定性好,理论上是可靠的重建方式。

Objective The clinical outcomes of 3D-printed tumor endoprosthesis for the defect of distal tibia after tumor resection are satisfactory,but the current analysis of its biomechanical properties is limited.To provide theoretical basis for clinical application,a finite element analysis was used to detect the initial strength of the structure.Methods Computerized tomography(CT)data of tibia and fibula from a healthy adult male volunteer were collected.Computer-aided design software was used to established three-dimension models.Two different models were constructed:normal tibia-fibula-talus complex and prosthetic reconstruction.Mechanical analysis was carried out by finite element method with ANSYS software.The contact relation between screw and prosthesis was binding contact,the contact relation between prosthesis and cortical bone was slip contact,and the contact relation between screw and cortical bone was binding contact.Simulated loads of 600 N were applied to the tibial plateau to simulate balanced single-foot standing.With the vertical axis of the tibia as the rotation center,2.7 N·m clockwise and counterclockwise were applied on the tibial plateau to simulate the external rotation load and internal rotation load of the lower limbs.Results When 600 N vertical stress was applied to the tibial plateau,the maximum von Mises compressive stress of the normal tibia-fibular model was 8.27 MPa,and the concentrated area of stress located at the posterior cortex bone in the middle part of the tibia.The maximum deformation site of the model was the lateral tibial plateau and the fibula head,and the deformation distance was 4 mm.When the clockwise and counterclockwise moments of 2.7 N·m were applied,the maximum von Mises compressive stress was 14.25 MPa in the middle tibial cortex,and the maximum displacement point was 2.47 mm in the anterior proximal tibial cortex.In the simulation of one-leg standing,the maximum von Mises compressive stress of the model was 51.98 MPa,located at a cross screw at the distal end of the model.Otherwise,the rest of the model was subjected to uniform stress.The deformation analysis showed that the maximum displacement of the prosthetic body weight model was smaller than that of the normal tibia and fibula model,only 0.74 mm,and it was located on the lateral tibia plateau and the fibula head,which was consistent with the normal tibia and fibula model.When 2.7 N·m clockwise and counterclockwise moments were applied,the maximum von Mises compressive stress was 15.44 MPa and was located at the antirotating screw at the distal end of the implant,and the maximum displacement point was only 0.07 mm at the lateral tibial platform and the release site of the fibula head during rotation.Conclusions The 3D printed prosthesis is a reliable reconstruction method in the bone defect model of the lower tibial segment after resection of the malignant bone tumor,by which the prosthesis and bone will have uniform force and good stability.