椎间隙注入不同弹性模量骨水泥对邻近上下椎体应力的影响

Effect of bone cement with different elastic moduli injected into intervertebral space on stress of adjacent upper and lower vertebrae

背景:近年来,针对腰椎间盘退变和椎间隙变窄所引起的腰部反复疼痛病症从国外引入了椎间隙注入骨水泥的治疗方法,但部分患者在治疗后出现椎体骨折的情况,原因可能是骨水泥弹性模量不佳。目的:通过腰椎三维有限元模型分析椎间隙中注入不同弹性模量骨水泥对上下椎体表面最大应力的影响。方法:招募1名脊柱正常志愿者获取CT数据,利用Mimics、Geomagic、SolidWorks、Ansys建立腰椎L_(2)-L_(5)有限元模型,随后建立L_(3)-L_(4)椎间隙注射不同剂量(1 mL与4 mL)骨水泥模型,每种剂量下赋予骨水泥4种弹性模量(1000,2000,4000,8000 MPa),在L_(2)椎体表面施加压力与弯矩,分析L_(3)椎体下表面与L_(4)椎体上表面的应力。结果与结论:①在骨水泥注入量相同的情况下,随着骨水泥弹性模量的增大,L_(3)椎体下表面与L_(4)椎体上表面的应力增加,其中弹性模量1000 MPa骨水泥对L_(3)椎体下表面与L_(4)椎体上表面的应力影响最小,弹性模量8000 MPa骨水泥对L_(3)椎体下表面与L_(4)椎体上表面的应力影响最大,不同弹性模量骨水泥对整个腰椎活动度的影响较小;②结果说明,在满足治疗要求的情况下注入较低弹性模量的骨水泥可以降低术后骨折风险。

BACKGROUND:In recent years,the treatment method of injecting bone cement into the intervertebral space has been introduced from abroad for the treatment of lumbar recurrent pain caused by lumbar disc degeneration and intervertebral space narrowing;however,some patients had vertebral fractures after treatment;the fracture may occur because the bone cement injected into the intervertebral space has a poor elastic modulus.OBJECTIVE:To analyze the effect of bone cement with different elastic moduli injected into the intervertebral space on the maximum stress of upper and lower vertebrae using a three-dimensional finite element model.METHODS:A volunteer with normal spine was recruited to obtain CT data.The finite element model of L_(2)-L_(5)lumbar spine was established using Mimics,Geomagic,SolidWorks,and Ansys.Subsequently,a L_(3)-L_(4)intervertebral space injection model with different doses(1 mL and 4 mL)of bone cement was established.Four different elastic moduli(1000,2000,4000,and 8000 MPa)were assigned to bone cement at each dose.Pressure and bending moment were applied on the surface of the L_(2)vertebral body to analyze the stress on the lower surface of the L_(3)vertebral body and the upper surface of the L_(4)vertebral body.RESULTS AND CONCLUSION:(1)In the case of the same amount of bone cement injection,as the elastic modulus of bone cement increased,the stress on the lower surface of L_(3)vertebral body and the upper surface of L_(4)vertebral body increased.Among them,the bone cement with an elastic modulus of 1000 MPa had the least effect on the lower surface of L_(3)vertebral body and the upper surface of L_(4)vertebral body.Bone cement with elastic modulus of 8000 MPa had the greatest effect on the lower surface of L_(3)vertebral body and the upper surface of L_(4)vertebral body.Bone cement with different elastic moduli had little effect on the motion range of the whole lumbar spine.(2)The results indicate that injecting bone cement with lower elastic modulus while meeting treatment requirements can reduce the risk of postoperative fractures.