有限元模型建立青少年骶椎腰化的验证分析

Establishment and validation of a finite element model of sacral lumbarization in adolescents

背景:腰椎骶化会使椎体节段发生变化,从而导致在运动中引起腰痛。流行病学研究显示,青少年腰椎骶化的发病率逐年升高。目的:建立青少年骶椎腰化患者的三维有限元模型,分析骶椎腰化患者在模拟正常运动条件下腰椎力学特性及应力应变规律,为临床中骶椎腰化引起的腰痛治疗提供力学依据。方法:选择1例骶椎腰化16岁男性青少年患者的CT影像,利用mimics 16.0初步建立腰椎数据的三维模型、导入Geomagic studio和ANASYS WorkBench软件采用三维数字医学建模方法,建立包括椎间盘的下腰段和骶段有限元模型。通过施加2 N·mm的力矩模拟加载正常人体载荷后前屈、后伸、左侧弯、右侧弯运动对模型进行生物力学测试,分析各工况条件下移位椎的力学变化特性。试验于2018-03-05经内蒙古医科大学伦理委员会批准,批准号YKD2018015。结果与结论:在伸屈活动时L_(5)及S_(1)椎弓根承受应力显著大于侧弯活动,移行的S_(1)椎弓根应力变化方向与正常成人L_(5)椎弓根峡部应力变化方向相同。青少年骶椎腰化患者,移行椎在腰椎活动中,S_(1)椎弓根峡部所承受的应力明显大于L_(5)椎弓根峡部,其小关节突及椎间盘承受应力更大。提示对于青少年骶椎腰化患者,在腰椎活动中随着移行椎的应力增大,更易造成疲劳骨折及峡部裂,而小关节突及椎间盘承受应力的增加,使其易出现退变。

BACKGROUND:Lumbar sacralization will cause changes in the vertebral body segments,resulting in low back pain during exercise.Epidemiological studies showed that the incidence of lumbar sacralization in adolescents is increasing year by year.OBJECTIVE:To establish a three-dimensional finite element model of adolescent patients with lumbar sacral vertebrae,and to analyze the mechanical properties and stress-strain rules of lumbar vertebrae under simulated normal exercise conditions,so as to provide mechanical basis for the treatment of low back pain caused by sacral lumbarization in clinic.METHODS:The CT images of a 16-year-old male teenager with sacral lumbarization were selected,and the threedimensional model of lumbar data was established by mimics16.0,and the three-dimensional digital medical modeling method was introduced into Geomagic Studio and ANASYS WorkBench software to establish the finite element model of the lower lumbar and sacral segments of the intervertebral disc.The biomechanical test of the model was carried out by applying the moment of 2 N•mm to simulate the movement of flexion,extension,left bending and right bending after loading normal human body load,and the mechanical changes of displaced vertebrae under various working conditions were analyzed to explore the mechanical characteristics of lumbar sacral vertebrae in adolescents.This trial was approved by the Ethics Committee of Inner Mongolia Medical University(approval No.YKD2018015)on March 5,2018.RESULTS AND CONCLUSION:During extension and flexion,the stress of L_(5) and S_(1) pedicles was significantly greater than that of scoliosis.The direction of stress change of the migration S_(1) pedicle was the same as that of normal adult L_(5) pedicle isthmus.In juvenile patients with sacral lumbarization,during lumbar spine movement,the stress on the S_(1) pedicle isthmus was significantly greater than that on the L_(5) pedicle isthmus,and the facet joints and intervertebral discs bore greater stress.It is concluded that for adolescents with complete sacral lumbarization,as the stress on the transitional vertebrae increases during lumbar activities,it is more likely to cause fatigue fractures and isthmic fissures,while the facet joints and intervertebral discs are more stressed,making them prone to regression change.