角度人工颈椎间盘置换对关节突应力的影响

EFFECTS OF NOVEL ANGLED CERVICAL DISC REPLACEMENT ON FACET JOINT STRESS

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。

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.