椎体后凸成形骨水泥注射治疗的有限元模型数字化评价

背景:由于经皮椎体后凸成形的治疗原理、远期疗效、并发症均与其生物力学密切相关,其生物力学引起了广泛关注。目的:建立椎体后凸成形骨水泥注射治疗后的生物力学变化及骨水泥泄漏虚拟数字化评价系统。方法:在前期实验已建立的L3-L5三维模型的基础上进行椎体后凸成形骨水泥注射操作,并导入Abaqus2016软件将模型立体化,进行有限元分析,分析骨水泥注射方式、注射压力及注射量对L4骨折椎体终板应力的影响。结果与结论:①模拟经皮椎体后凸成形手术操作填充骨水泥后,L4骨折椎体终板在骨水泥的承载分压作用下应力明显降低。不同注射方式对L4骨折椎体终板所受应力影响不显著(P> 0.05),但双侧注射使骨水泥分布更加均匀,效果最好;②不同注射压力对L4骨折椎体终板所受应力影响不显著(P> 0.05),但随着注射压力的增加,骨水泥分布更加分散,更容易出现渗漏;③随着骨水泥注射剂量逐渐增加,L4骨折椎体终板应力逐渐降低(P<0.05),注射2 mL时不能恢复椎体的生理刚度,4 mL时骨水泥分布更加集中,8 mL时达到屈服点;④骨水泥注射后,下位椎体上终板比上位椎体下终板更容易出现再骨折的情况:⑤结果表明,模拟手术前后L4椎体终板应力发生明显转移,即L4上终板应力增加,L4下终板应力减少;不同注射方式对手术结果影响不大,但双侧注入的骨水泥分布更加均匀,降低了术后再次骨折和塌陷的概率;选用低注射压力可降低术后骨水泥泄露风险;4 mL注射量既能使病椎恢复较好的刚度及生理曲度又未达到屈服点而引起再次骨折。

Digital evaluation of finite element model for percutaneous kyphoplasty with bone cement injection

BACKGROUND:The treatment principle,long-term therapeutic effects,and complications of percutaneous kyphoplasty are closely related to biomechanics.Its biomechanics have attracted wide attention.OBJECTIVE:To establish a virtual digital evaluation system for biomechanical changes and bone cement leakage after percutaneous kyphoplasty and bone cement injection.METHODS:Percutaneous kyphoplasty with bone cement injection was performed based on previously established three-dimensional model of L3-L5.The model was processed using the software Abaqus 2016 for finite element analysis.The effects of bone cement injection model,injection pressure,and injection volume on the stress of fractured L4 vertebral endplate were analyzed.RESULTS AND CONCLUSION:(1) After simulated percutaneous kyphoplasty with bone cement injection,the stress of L4 fractured vertebral endplate decreased significantly under the partial pressure of cement.Different injection methods had no significant effect on the stress of fractured L4 vertebral endplate(P> 0.05),but bilateral injection made the distribution of bone cement more uniform and produced the best effect.(2) Different injection pressures had no significant effect on the stress of fractured L4 vertebral endplate(P> 0.05),but with the increase of injection pressure,the distribution of bone cement was more dispersed and leakage was more likely to occur.(3) With increase in bone cement injection dose,the stress of fractured L4 vertebral endplate gradually decreased(P <0.05).The physiological stiffness of the vertebral body could not be restored when 2 mL of bone cement was injected.The distribution of bone cement was more concentrated when 4 mL of bone cement was injected.The breakdown point was reached when 8 mL of bone cement was injected.(4) After injection of bone cement,the upper endplate of the lower vertebral body was more prone to suffer from fracture than the lower endplate of the upper vertebral body.(5)These results suggest that the stress of L4 vertebral endplate shifted obviously after simulated surgery compared with before surgery,that is,the stress of L4 upper endplate increased and that of L4 lower endplate decreased.Different injection methods had little effect on the surgical results,but the distribution of bone cement injected bilaterally was more uniform,which reduced the incidences of re-fracture and collapse.Lower injection pressure could reduce the risk of cement leakage after surgery.Injection of 4 mL bone cement can restore good stiffness and physiological curvature of the diseased vertebra,without reaching the yield point or causing refracture.