青少年颈椎间盘突出症有限元模型建立及应力分析

Establishment and stress analysis of a finite element model for adolescent cervical disc herniation

背景:颈椎间盘突出症可引起肩颈部疼痛、上肢放射性疼痛,发病率逐年上升并趋于年轻化,充分了解青少年颈椎生物力学特点,对于延缓青少年颈椎间盘突出症具有重要意义。目的:利用有限元分析技术重建正常青少年及青少年颈椎间盘突出症患者的颈椎模型,分析C_(1)-T_(1)颈椎椎体活动度和纤维环、髓核、终板及小关节软骨的生物力学特征。方法:选择正常青少年和青少年颈椎间盘突出症患者各1例,将连续扫描的颈椎CT原始影像数据以DICOM格式导入Mimics 21.0,分别重建C_(1)-T_(1);随后将建立好的模型导入3-Matic软件进行椎间盘重建,将完善的模型导入Hypermesh软件,对椎体、髓核、纤维环、韧带进行网格划分,生成有效的几何模型,赋予材料属性后将最终模型导入ABAQUS软件中。观察C_(1)-C_(7)各节段颈椎椎体在不同工况下的关节活动度,并分析各节段颈椎纤维环、髓核、终板及小关节软骨的生物力学特征。结果与结论:(1)正常青少年与颈椎间盘突出症青少年患者颈椎模型C1在6种工况下的关节活动度均高于其他椎体,且正常青少年各节段颈椎椎体活动度均大于颈椎间盘突出症青少年患者;(2)正常青少年颈椎模型纤维环及髓核应力最大值在C_(2-3)左侧屈工况(0.43 MPa,0.17 MPa),颈椎间盘突出症青少年患者颈椎模型应力最大值在C_(7)-T_(1)左侧屈工况(0.54 MPa,0.18 MPa);(3)正常青少年颈椎模型终板应力最大值在C_(3)上终板左侧屈工况(1.46 MPa),颈椎间盘突出症青少年患者模型终板应力最大值在C7下终板左侧屈工况(1.32 MPa);(4)正常青少年颈椎小关节软骨应力最大值在C_(2-3)左旋转工况(0.98 MPa),颈椎间盘突出青少年患者的小关节软骨在不同工况下以C_(1-2)应力增加最明显,应力最大在左侧屈(3.50 MPa);(5)提示与正常青少年相比,颈椎间盘突出症青少年患者颈椎曲度改变,颈椎整体关节活动度下降;颈椎间盘突出症青少年患者纤维环、髓核及终板在C_(7)-T_(1)节段应力明显增大;C_(1-2)左侧小关节软骨应力明显,颈椎曲度异常可能是引起应力改变的主要因素。

BACKGROUND:Cervical disc herniation can cause pain in the neck and shoulder area,as well as radiating pain in the upper limbs.The incidence rate is increasing year by year and tends to affect younger individuals.Fully understanding the biomechanical characteristics of the cervical spine in adolescents is of great significance for preventing and delaying the onset of cervical disc herniation in this age group.OBJECTIVE:To reconstruct cervical spine models for both healthy adolescents and adolescent patients with cervical disc herniation utilizing finite element analysis techniques,to analyze the motion range of the C_(1)-T_(1)cervical vertebrae as well as the biomechanical characteristics of the annulus fibrosus,nucleus pulposus,endplates,and the cartilage of the small joints.METHODS:A normal adolescent’s cervical spine and an adolescent patient with cervical disc herniation were selected in this study.The continuous scan cervical spine CT raw image data were imported into Mimics 21.0 in DICOM format.The C_(1)-T_(1)vertebrae were reconstructed separately.Subsequently,the established models were imported into the 3-Matic software for disc reconstruction.The perfected models were then imported into Hypermesh software for meshing of the vertebrae,nucleus pulposus,annulus fibrosus,and ligaments,creating valid geometric models.After assigning material properties,the final models were imported into ABAQUS software to observe the joint motion range of the C_(1)-C_(7)cervical vertebrae segments under different conditions,and to analyze the biomechanical characteristics of the annulus fibrosus,nucleus pulposus,endplates,and small joint cartilage of each cervical spine segment.RESULTS AND CONCLUSION:(1)In six different conditions,the joint motion range of the C_(1) vertebra in the cervical spine models of both normal adolescent and adolescent patient with cervical disc herniation was higher than that of the other vertebrae.Additionally,the joint motion range of each cervical spine segment in normal adolescent was greater than that in adolescent patient with cervical disc herniation.(2)In the cervical spine model of normal adolescent,the maximum stress values in the annulus fibrosus and nucleus pulposus were found on the left side during C_(2-3)flexion conditions(0.43 MPa and 0.17 MPa,respectively).In the cervical spine model of adolescent patient with cervical disc herniation,the maximum stress values were found on the left side during C_(7)-T_(1)flexion conditions(0.54 MPa and 0.18 MPa,respectively).(3)In the cervical spine model of normal adolescent,the maximum stress value on the endplate was found on the left side of the upper endplate of C_(3)during flexion conditions(1.46 MPa).In the model of adolescent patient with cervical disc herniation,the maximum stress value on the endplate was found on the left side of the lower endplate of C7 during flexion conditions(1.32 MPa).(4)In the cervical spine model of normal adolescent,the maximum stress value in the small joint cartilage was found in the C_(2-3)left rotation conditions(0.98 MPa).In adolescent patient with cervical disc herniation,the stress in the small joint cartilage significantly increased under different conditions,especially in C_(1-2),with the maximum stress found during left flexion(3.50 MPa).(5)It is concluded that compared to normal adolescent,adolescent patient with cervical disc herniation exhibits altered cervical curvature and a decrease in overall joint motion range in the cervical spine.In adolescent with cervical disc herniation,there is a significant increase in stress on the annulus fibrosus,nucleus pulposus,and endplates in the C_(7)-T_(1)segment.The stress on the left articular cartilage of the C_(1-2)is notable.Abnormal cervical curvature may be the primary factor causing these stress changes.