应用有限元对比分析椎体成形术中单侧入路退针法与双侧固定点注射骨水泥的生物力学变化

Biomechanical changes following bone cement injection by unilateral approach needle withdrawal versus bilateral fixation point during vertebroplasty:Finite element analysis

背景:要使椎体成形术单侧入路获得双侧入路的力学分布效果,需要改进单侧入路的穿刺路径及注射方法。在前期临床实践中作者设计了三维穿刺导向器,在其导引下穿刺到位理想,采用退针注射法注射骨水泥,使得骨水泥在椎体内分布更加合理,临床效果得到了提高,但是否在力学分布上与双侧相同?目的:应用有限元分析椎体成形过程中单侧入路退针法注射骨水泥的生物力学变化,并与双侧固定点注射骨水泥的方法对比。方法:采用的原始影像来自一位男性患者,76岁,L1椎体骨质疏松性疼痛。患者伤椎采用单侧入路退针法注射实施椎体成形术,进针点选择左侧椎弓根近中心部位,内倾角度为24.5°,先将针穿刺到达椎体的前中1/3部位,注射骨水泥3mL,然后缓慢向后退针至椎体的1/2部位,并停留3min,注射2mL,再退针到椎体的中后1/3部位注射1mL。模拟双侧入路,每侧注入3mL骨水泥,获取椎体L1～2节段断层图像,分别建立有限元模型,对椎体上表面分别依次施加载500,1000,1500,2000,2500N的轴向压缩负载,进行生物力学对比分析。结果与结论:随着施加负载的增加,应变和应力也逐渐增加,椎体呈现弹性性质,出现了近似线性的小变形情况。双侧固定点和退针注射法注射骨水泥在轴向压缩不同负载下应力和应变差异无显著性意义(P>0.05)。提示椎体成形过程中单侧入路退针注射法和双侧固定点注射骨水泥的生物力学分布无明显差异。

BACKGROUND：The puncture approach and injection method of unilateral approach should be improved to obtain mechanical distribution of bilateral approach.Preliminary studies designed three-dimensional puncture guider and utilized withdrawal injection of bone cement,which improved clinical effect.However,the mechanical distribution of unilateral approach versus bilateral approach remains unclear.OBJECTIVE：To analyze biomechanical changes during vertebroplasty with unilateral approach and withdrawal injection using a finite element analysis and compare with bilateral approach.METHODS：The primary image was from a male patient,76 years old,with L1 osteoporosis and pain.The patient was subjected to operation in the injured vertebrae by unilateral approach,and the needle entrance point was at the left center of pedicle,with an oblique angle of 24.5°.The needle was inserted into the front one third of vertebrae body and 3 mL bone cement was injected.The needle was withdrawn to the middle of the vertebrae,maintained for 3 minutes,and 2 mL bone cement was injected.The needle was withdrawn to the posterior 1/3 of the vertebrae body,followed by injection of 1 mL bone cement.Bilateral approach was simulated,and each side was injected with 3 mL bone cement.L1-2 fault image was obtained and finite element model was established.Vertebral biomechanics was compared under loads of 500,1 000,1 500,2 000,and 2 500 N on the supine surface.RESULT AND CONCLUSION：The strain and stress were increased with increasing load.The vertebral bodies showed property of elasticity,and nearly linear minor deformity.There were no differences in stress distribution and deformity between bilateral fixation point and withdrawl injection of bone cement （P 0.05）.Results show that unilateral approach withdrawl injection of bone cement displayed similar biomechanics as bilateral fixation point during vertebroplasty.