胫骨后倾角对前交叉韧带及膝关节稳定性影响的三维有限元分析

The Influence of Posterior Tibial Slope on the Anterior Cruciate Ligament and Knee Joint Stability

目的:探讨胫骨平台后倾角对前交叉韧带及膝关节稳定性的生物力学影响。方法:选择一名健康志愿者行左侧膝关节CT及MRI扫描,测量胫骨平台后倾角为7°。将扫描数据导入Mimics软件,获得骨、软骨、半月板、韧带等结构的三维模型,然后利用Geomagic对图像进行修饰,再导入Solidworks软件中建立伸直位膝关节三维模型。利用Solidworks软件建立2°和12°两种不同后倾角的膝关节三维模型。在建立三组膝关节伸直位模型后,每组模型再分别建立屈膝30°和90°的模型。将膝关节不同三维有限元模型导入ANSYS有限元分析软件中,给予加载负荷进行计算分析:伸直位模型胫骨固定,股骨侧给予施加1150 N的垂直负荷;屈膝30°模型胫骨固定,股骨施加750 N垂直负荷及10 N·m的外旋负荷;屈膝90度模型股骨侧固定,胫骨侧施加134 N的前向负荷。在各模型中分析ACL及胫骨-股骨的相对位移。结果:计算机三维有限元分析显示,在伸膝状态下,ACL承受的张力随着胫骨后倾角的增加而增加:PTS为2°时ACL张力为12.195 N,7°时为12.639 N,12°时为18.658 N;胫骨-股骨相对位移:PTS为2°时为2.735 mm,7°时为3.086 mm,12°时为3.881 mm。在屈膝30°的模型中,前叉韧带所承受的最大张力如下:2°时为24.585 N,7°时为25.612N,12°时为31.481 N;胫骨-股骨位移为:2°时为5.590 mm,7°时为6.721 mm,12°时为6.952 mm。在屈膝90°的模型中,前叉韧带所承受的最大张力如下:2°时为5.119 N,7°时为8.674 N,12°时为9.314 N;胫骨-股骨位移为:2°时为0.276 mm,7°时为0.577 mm,12°时为0.602 mm。结论:在膝关节承受应力时,随着PTS的增加,ACL承受的张力和胫骨-股骨之间相对位移都随之增大,较大的PTS可能是ACL损伤的危险因素。

Objective To explore the biomechanical influence of posterior tibial slope （PTS）on the anterior cruciate ligament and knee joint stability. Methods The left knee joint of a healthy volunteer was scanned by CT and MRI at 7 degree of PTS. The data of CT and MRI scans were imported into Mimics software to obtain 3D model of bone,cartilage,meniscus and ligament,and then Geomagic software was used to modify of the image. The 3D model of knee joint in extension with 7° of PTS,3D models with 2° of PTS and 12° of PTS,and 3D models with 30° and 90° of knee joint flexion were respectively established through importing the 3D model of bone,cartilage,meniscus and ligament into Solidworks software. Each 3D finite element knee model was imported into ANSYS software,and then applied 1150 N vertical stress on the femur of extension model,750 N vertical stress and lateral rotary torque of 10 N·m on the femur of 30° of flexion model,and 134 N forward stress on tibia of 90° of flexion model. And the relative displacement between tibia and femur and the stress of ACL were recorded simultaneously. Results Under the knee extension,ACL tensions were 12.195 N in the model with 2° of PTS, 12.639 N in the model with 7° of PTS,and 18.658 N in the model with 12° of IrFS;The relative displacements between the tibia and femur were 2.735 mm in the model with 2° of PTS,3.086 mm in the model with 7° of FFS,and 3.881 mm in the model with 12° of PTS.Under the 30° of knee flexion,ACl, tensions were 24.585 N in the model with 2° of PTS,25.612 N in the model with 7° of PTS,and 31.481 N in the model with 12° of PTS;The relative displacements between the tibia and femur were 5.590 mm in the model with 2° of IRFS,6.721 mm in the model with 7° of PTS,and 6.952 mm in the model with 12° of PTS. Under the 90° of knee flexion,ACL tensions were 5.119 N in the model with 2° of PTS, 8.674 N in the model with 7° of PTS,and 9.314 N in the model with 12° of PTS;The relative displacements between the tibia and femur were 0.276 mm in the model with 2° of PTS,0.577 mm in the model with 7° of PTS,and 0.602 mm in the model with 12° of PTS. Conclusion When applying the stress on the knee joint,the tension of ACI, and the relative displacement between libia and femur increased with the increasing of PTS. Steeper PTS could be a risk factor for ACI, injury.