前交叉韧带重建术后移植物应力的有限元分析

目的: 探究前交叉韧带(anterior cruciate ligament, ACL)重建后移植物应力分布特征,为ACL重建的手术方案提供理论参考。方法: 基于三维磁共振及CT影像,建立完整膝关节有限元模型,模型包括股骨、胫骨、腓骨、内侧副韧带、外侧副韧带、ACL、后交叉韧带;建立ACL重建后膝关节有限元模型,模型包括股骨、胫骨、腓骨、内侧副韧带、外侧副韧带、ACL移植物、后交叉韧带。模型采用线弹性材料属性,骨组织材料属性设置为弹性模量17 GPa,泊松比(Poisson’s ratio)为0.36;完整膝关节及ACL重建膝关节的模型中的韧带组织及ACL移植物的材料属性设置为弹性模量390 MPa,泊松比0.4;将股骨固定设置为模型边界条件,施加胫骨前向134 N的拉力为载荷条件,求解分析完整膝关节的ACL及重建术后的ACL移植物的拉应力、压应力、剪切应力、等效应力的受力状态。结果: 重建后的ACL移植物的最大压应力(6.34 MPa)、等效应力(5.9 MPa)、剪切应力(1.83 MPa)均在前侧股骨端,与完整膝关节ACL最大压应力(8.77 MPa)、等效应力(8.88 MPa)、剪切应力(3.44 MPa)位置一致。移植物最大拉应力也出现在股骨端,但位置在后侧,与完整膝关节ACL最大拉应力位置一致,且ACL移植物最大拉应力的值仅为0.88 MPa,小于完整膝关节ACL的2.56 MPa。结论: ACL移植物压应力、等效应力、剪切应力最大值均在前侧股骨端,最大拉应力出现在股骨端后侧,均与完整膝关节ACL最大拉应力位置一致;ACL移植物的前侧部分承受力较大,后侧部分承受力较小,与ACL的生物力学特性相符合。

Finite element analysis of the graft stresses after anterior cruciate ligament reconstruction

Objective: To explore the stress distribution characteristics of the graft after anterior cruciate ligament (ACL) reconstruction, so as to provide theoretical reference for the surgical plan of ACL reconstruction. Methods: Based on 3D MRI and CT images, finite element models of the uninjured knee joint and knee joint after ACL reconstruction were established in this study. The uninjured knee model included femur, tibia, fibula, medial collateral ligament, lateral collateral ligament, ACL and posterior cruciate ligament. The ACL reconstruction knee model included femur, tibia, fibula, medial collateral ligament, lateral collateral ligament, ACL graft and posterior cruciate ligament. Linear elastic material properties were used for both the uninjured and ACL reconstruction models. The elastic modulus of bone tissue was set as 17 GPa and Poisson’s ratio was 0.36. The material properties of ligament tissue and graft were set as elastic modulus 390 MPa and Poisson’s ratio 0.4. The femur was fixed as the boundary condition, and the tibia anterior tension of 134 N was applied as the loading condition. The stress states of the ACL of the intact joint and the ACL graft after reconstruction were solved and analyzed, including tension, pressure, shear force and von Mises stress. Results: The maximum compressive stress (6.34 MPa), von Mises stress (5.9 MPa) and shear stress (1.83 MPa) of the reconstructed ACL graft were all at the anterior femoral end. It was consistent with the position of maximum compressive stress (8.77 MPa), von Mises stress (8.88 MPa) and shear stress (3.44 MPa) in the ACL of the intact knee joint. The maximum tensile stress of the graft also appeared at the femoral end, but at the posterior side, which was consistent with the position of the maximum tensile stress of ACL of the uninjured knee joint. More-over, the maximum tensile stress of the graft was only 0.88 MPa, which was less than 2.56 MPa of ACL of the uninjured knee joint. Conclusion: The maximum compressive stress, von Mises stress and shear stress of the ACL graft are located in the anterior femoral end, and the maximum tensile stress is located in the posterior femoral end, which is consistent with the position of the maximum tensile stress of the ACL of the uninjured knee joint. The anterior part of ACL and the graft bore higher stresses than the posterior part, which is consistent with the biomechanical characteristics of ACL.