骨质疏松性椎体压缩骨折强化术后骨组织-骨水泥界面生物力学应力再平衡机制的有限元研究

Study on the mechanism of biomechanical stress rebalancing at the bone tissue-bone cement interface after reinforcement of osteoporotic vertebral compression fracture based on finite element method

目的:明确脊柱骨质疏松性椎体压缩骨折(osteoporotic vertebral compression fracture,OVCF)骨水泥强化治疗后骨组织-骨水泥界面的生物力学应力再平衡机制及脊柱动态稳定重建效应。方法:选择甘肃中医药大学附属医院脊柱外科收治的OVCF患者(伤椎为T12和L1)为研究对象,提取薄层高精度的胸腰段CT影像数据,通过Mimics、Geomagic、Solidworks、Ansys Workbench有限元生物力学建模平台,建立三维数字化仿真生物力学模型,对伤椎运动节段在轴向、前屈、后伸、侧弯及旋转等不同运动工况下骨组织-骨水泥界面的等效应力进行量化研究。结果:脊柱OVCF骨水泥强化术后骨组织-骨水泥界面的等效应力极值和分布区间较术前明显优化,在轴向、前屈、后伸、侧弯及旋转等运动工况下,T12伤椎骨水泥强化治疗术后的最大主应力相比于术前显著下降,在相同的运动工况下分别为33.002MPa、35.639MPa、35.98MPa、60.458MPa、65.396MPa、60.177MPa、42.249MPa,尤其是前屈运动工况下,脊柱T12伤椎的最大主应力从术前的77.995MPa下降至术后的35.639MPa;在同样的运动工况下,L1伤椎强化治疗术后的最大主应力分别为24.911MPa、34.705MPa、26.514MPa、60.144MPa、32.797MPa、30.259MPa、32.894MPa,其中在轴向、前屈运动工况下,L1伤椎骨界面的最大主应力由术前的74.798MPa、99.232MPa下降至术后的24.911MPa、34.705MPa,脊柱T12、L1伤椎骨水泥界面的最大主应力分布弥散较为均匀,T12伤椎松质骨界面主应力极值主要分布在1.004MPa~3.0758MPa区间,L1伤椎松质骨界面主应力极值分布区间为1.8075MPa~2.3355MPa,应力分布云图显示,伤椎强化术后骨界面的应力分布向中后柱转移,应力集中得到纠正,骨组织-骨水泥界面的应力分布趋向于均衡稳定化。结论:胸腰段伤椎骨水泥强化术后重建了脊柱的动态生物力学稳定性,骨组织-骨水泥界面的生物力学应力应变刺激相比于术前显著下降,应力呈现出均匀弥散分布特征,重建了骨组织-骨水泥界面的应力再平衡。

Objectives:To clarify the biomechanical stress rebalancing mechanism at the bone tissue-cement interface and the dynamic stability reconstruction effect on the spine after cement reinforcement treatment of osteoporotic vertebral compression fractures(OVCF).Methods:An OVCF patient(injured vertebrae,T12 and L1)treated in the Department of Spine Surgery of the Affiliated Hospital of Gansu University of Traditional Chinese Medicine was selected as the object of study,and thin-layer,high-precision thoracic and lumbar vertebral CT imaging data of the patient was extracted.A 3D digitally simulated biomechanical model was established through the finite-element biomechanical modeling platforms of Mimics,Geomagic,Solidworks,and Ansys Workbench,in order to quantitatively study the equivalent stress at bone tissue-cement interface of motion segment of the injured vertebral body under different motion conditions such as axial,flexion,extension,lateral bending,and rotation.Results:The extreme value and distribution range of equivalent stress at the bone tissue-bone cement interface after spinal OVCF were significantly optimized compared with those before surgery.Under the motion conditions of axial,forward flexion,posterior extension,lateral bending and rotation conditions,the maximum principal stress after spinal cement reinforcement for T12 vertebra decreased significantly compared with that before surgery,which was 33.002MPa,35.639MPa,35.98MPa,60.458MPa,65.396MPa,60.177MPa,and 42.249MPa under the same working conditions,especially under the forward flexion working conditions,the maximum principal stress of T12 decreased from 77.995MPa before surgery to 35.639MPa after surgery;Under the same motion conditions,the maximum principal stress of L1 vertebra after reinforcement treatment was 24.911MPa,34.705MPa,26.514MPa,60.144MPa,32.797MPa,30.259MPa,and 32.894MPa,respectively,and under axial and forward flexion conditions,the maximum principal stress of L1 vertebra decreased from 74.798MPa and 99.232MPa before surgery to 24.911MPa and 34.705MPa after surgery.The maximum principal stress at T12 and L1 bone cement interface distributed evenly.The extreme value of principal stress at T12 cancellous bone was 1.004MPa to 3.0758MPa,which at L1 cancellous bone was 1.8075MPa to 2.3355MPa.The stress distribution cloud map showed that the stress distribution at bone interface shifted to the middle and posterior columns after the reinforcement treatment,and the stress concentration was corrected.The stress distribution at the bone tissue-bone cement interface tended to be balanced and stabilized.Conclusions:The dynamic biomechanical stability of the spine is reconstructed after cemented reinforcement of the injured vertebrae in the thoracolumbar segment,and the biomechanical stress-strain stimulus at the bone tissue-cement interface is significantly decreased compared with the preoperative period,and the stresses are distributed evenly,which reconstruct the stress rebalancing at the bone tissue-cement interface.