不同方法治疗骨质疏松性胸腰椎压缩骨折椎体力学稳定性变化差异的有限元分析

Finite element analysis of different treatments in mechanical stability of osteoporotic vertebral compression fractures

目的:通过有限元分析不同微创治疗方法对骨质疏松性椎体压缩骨折(OVCF)伤椎高度恢复不全状态下与人体正常模型、骨质疏松症(OP)患者模型进行对比分析,结合临床实际针对T12、L1椎体在骨折治疗后椎体高度丢失相同状态下不同工况条件对脊柱及相邻椎体附属结构的应力变化差异进行有限元分析,为OVCF的治疗筛选最佳的治疗策略和生物力学变化特征提供依据。方法:选择健康志愿者2人,X线检查排除胸腰椎相关病变,无明显畸形、增生、退变等,同时排除其他脊柱疾患病史、脊柱手术病史。另外选择2例住院老年骨质疏松女性胸腰椎CT及MRI扫描资料,通过PACS影像系统对符合条件的经过PKP、中医过伸复位法配合PKP、PVP治愈的临床真实病例6例,提取其CT及MRI资料,建立T11~L2三维有限元模型并验证模型有效性。施加生理正常载荷大小的轴向、前屈、后伸、侧屈载荷后求解,分析不同运动状态下的生物力学变化。对8组模型之间椎体、纤维环、椎间盘、髓核的Von Mises应力及椎体最大位移进行比对分析,同时对应力云图进行比对分析其生理与病理关节应力区域变化。结果:从椎体应力结果分析看,与正常人体脊柱胸腰段模型应力变化比较,经椎体强化术后PKP、PVP治疗在脊柱前屈、后伸、左右侧弯、左右旋转、轴向7种不同运动状态下,其椎体结构包括椎体、椎间盘、纤维环、髓核的Von Mises应力有明显增大趋势,而OP者上述指标有明显降低趋势,椎体最大位移呈现增大趋势。对于T12椎体压缩性骨折经骨水泥强化术后,其在左右旋转运动状态下椎体、关节突关节应力明显增大。纤维环、椎间盘的应力变化略低于正常人,其中T12~L1纤维环、椎间盘应力在L1椎体压缩性骨折经PKP治疗后明显高于正常人。髓核应力变化OP患者明显低于正常人,椎体强化术后高于正常人。对终板的应力变化影响主要体现在骨折椎体经骨水泥强化术后(PKP、PVK、手法配合PKP)对邻近椎体终板应力有明显的增加,这印证了临床中经椎体强化术后患者远期对邻近椎体退变有明显影响。与正常人体模型比较,从筋-骨系统进行分析,骨与肌肉、韧带所代表的动静力变化都明显降低。结论:采用中医过伸复位法配合PKP方法能使纤维环、椎间盘、髓核及相邻椎体终板、关节突软骨的应力变化幅度减小,趋于一种稳定状态,降低了远期伤椎高度丢失、并发再骨折以及相邻椎体再骨折的发生比率,提高其远期疗效和增加OVCF胸腰段治疗后筋骨系统的稳定性。对治疗OVCF风险预防策略的标准化建立和完善提供理论和生物力学依据。

Objective:By means of finite element analysis of different minimally invasive treatment methods,the finite element analysis of the difference of stress changes in spine and adjacent vertebral appendage structure in different working conditions of T12 and L1 vertebral body under the same condition of vertebral body height loss was carried out in combination with the normal model of human body and the model of osteoporosis(OP)patients under the condition of finite element analysis.Methods:Two healthy volunteers were selected,and X-ray examination excluded thoracic and lumbar spine related lesions,no obvious deformity,hyperplasia,degeneration,and the history of other spinal diseases and spinal surgery was excluded.In addition,2 CT and MRI scanning data of hospitalized elderly osteoporosis were selected,and 6 qualified clinical real cases cured by PKP,TCM overextension and PKP,PVP were selected through PACS imaging system,their CT and MRI data were extracted,the T11~L2 three-dimensional finite element model was established and the effectiveness of the model was verified.Apply axial,forward,rear extension and lateral yield load with physiological normal load size and analyze biomechanical changes in different moving states.The Von Mises stress of vertebral body,fiber ring,disc,nucleus and vertebral maximum displacement were analyzed,and the physiological and pathological joint stress regional changes were analyzed.Results:From the analysis of the vertebral stress results,after vertebral reinforcement PKP and PVP treatment was compared with the stress changes of the normal human spine chest and waist model in the spinal anterior flexion,posterior extension,left and right bending,left and right rotation,and axial movement states.The Von Mises stress of the vertebral structure includes vertebral,disc,fiber ring,and nucleus,OP patients were compared with normal human spine chest and waist section in 7 different exercise states,including spinal anterior flexion,posterior extension,left and right rotation,left and right rotation.The Von Mises stress of the vertebral structure including vertebral,disc,fiber ring,and nucleus pulla was significantly reduced,and the maximum displacement was increased.After the T12 vertebral compressive fracture,the joint stress of the vertebral body and joint protrusion increased significantly under the left and right rotation movement state.The stress changes of fiber ring and disc were slightly lower than normal people,and the T12~L1 fiber ring and disc stress were significantly higher than normal people after PKP treatment.Changes in nucleus myeloid stress in patients with OP were significantly lower than normal people and after vertebral reinforcement was higher than normal human body.The impact of the stress change on the final plate was mainly reflected in the significant increase of the fracture vertebral transcement reinforcement(PKP,PVK,technique with PKP)on the stress of the adjacent vertebral final plate,which confirmed that the significant impact on the adjacent vertebral degeneration after clinical transvertebral reinforcement.Compared with the normal mannequin model,from the tendon-bone system for analysis,the dynamic and dynamic force changes represented by the bone,muscle and ligaments were significantly reduced.Conclusion:The PKP method can reduce the stress changes of fiber ring,disc,nucleus and adjacent vertebral terminal plate and joint protrusion cartilage,tend to a stable state,reduce the long-term vertebral height loss,concurrent refracture and adjacent vertebral fracture,improve its long-term efficacy and increase the stability of muscles and bone system after OVCF chest and waist treatment.It provides a theoretical and biomechanical basis for the standardization and improvement of risk prevention strategies for treating OVCF.