角度人工颈椎间盘置换对关节突应力的影响

目的探讨带角度人工颈椎间盘置换后关节突及相邻关节突应力变化。方法选择400名西北地区40岁以上人群颈椎侧位X线片,计算机辅助设计软件测量颈椎间盘角,设计10°人工颈椎间盘;对已建立的C4、C5两节段带椎间盘的正常颈椎有限元模型、C4、5置换0°椎间盘假体和置换10°椎间盘假体后的颈椎模型进行轴向加压、前屈/后伸、侧弯、扭转加载,对比观察C4、5关节突应力变化;对已建立的C4～C6三节段带椎间盘的正常颈椎有限元模型、C4、5置换0°椎间盘假体和置换10°椎间盘假体后的颈椎模型同样方式进行加载,对比置换节段及相邻节段的关节突应力变化。结果 C3～C7椎间盘角分别为:C3、4(9.97±3.64)°,C4、5(9.95±4.34)°,C5、6(8.59±3.75)°,C6、7(8.49±3.39)°,各椎间隙之间椎间盘角两两比较,C3、4与C4、5,C5、6与C6、7差异无统计学意义(P>0.05),其余各椎间隙之间差异均有统计学意义(P<0.05)。C4、C5两节段模型加载中,轴向加载下三者等效剪应力(Se)无明显差异;前屈/后伸时正常模型Se最大,10°假体置换组最小;侧弯时正常椎体Se最大,10°假体置换组最小;扭转时10°假体置换组更接近正常椎体生理状态力学特性。C4～C6三节段模型加载中,C4、5节段的关节突关节Se在轴向加载、前屈/后伸、侧弯时较正常椎体明显减小;扭转时减小不明显,接近正常状态。相邻下位节段C5、6关节突应力在轴向加载和侧弯时应力明显减小,扭转时应力减小较少,前屈/后伸时无明显改变,接近正常节段力学特性。结论 10°椎间盘假体植入椎间隙对颈椎相邻节段的关节突应力影响小,接近正常颈椎间盘力学性能。

Effects of novel angled cervical disc replacement on facet joint stress

Objective To analyze the biomechanical changes of the adjacent cervical facet joints when the angled cervical prosthesis is replaced.Methods A total of 400 northwestern people were involved,with an age of 40 years or older.The cervical vertebra lateral X-ray films were taken,and the cervical angles were measured by professional computer aided design software,then the cervical intervertebral disc prosthesis with 10° angle was designed.The finite element models of C4,5 and C4-6 segments with intact cervical discs were developed;the C4,5 disc was replaced by the cervical prosthesis with 0° and 10° angle respectively;and then all models were subjected to axial loading,flexion/extension,lateral bending,and torsion loading conditions;the stress effects on adjacent facet joints after replacement were observed by comparing with that of the intact model.Results The cervical angles were(9.97 ± 3.64)° in C3,4,(9.95 ± 4.34)° in C4,5,(8.59 ± 3.75)° in C5,6,and(8.49 ± 3.39)° in C6,7,showing no significant difference between C3,4 and C4,5,C5,6 and C6,7(P > 0.05) and showing significant differences between the other cervical angles(P < 0.05).When C4,5 model was axially loaded,no significant difference in equivalent shearing stress were observed in intact,0°,and 10° groups;at flexion/extension loading,the stress was biggest in intact group,and was smallest in 10° group;at lateral bending,the stress got the high rank in intact group,and was minimum in 10° group;at torsion loading,the stress state of 10° group approached to the intact one condition.When C4-6 model was loaded,the facet joint stress of the replaced segment(C4,5) decreased significantly at axial loading,flexion/extension,and lateral bending;while no obvious decrease was observed at torsion loading;the stress of the adjacent inferior disc(C5,6) decreased significantly at axial loading and lateral bending condition,while less decrease was observed at torsion loading,no significant change at flexion/extension condition,it approached to that of the intact one.Conclusion The finite element analysis reveals that the biomechanical properties of 10° designed prosthesis is approximate to that of the intact cervical disc,thus the 10° designed prosthesis can meet the requirements of biomechanical function reconstruction of the cervical spine.