人工椎间盘置换对腰椎小关节应力影响的三维有限元分析

背景:近年来随着对脊柱生物力学研究的深入,人工椎间盘被认为是治疗腰椎退行性变较理想的方法,但目前对人工腰椎间盘的生物力学研究还非常有限.目的:建立腰椎运动节段人工椎间盘置换的三维有限元模型并进行生物力学分析,观察人工椎间盘置换对腰椎小关节应力的影响.方法:在已建立的正常腰椎运动节段三维有限元模型的基础上去除L4～5椎间盘、上下终板的有限元单元,加入SB-Chaite Ⅲ型人工椎间盘的有限元模型,保留L4～5椎间隙的纤维环及相关韧带,形成L4～5运动节段人工椎间盘置换的三维有限元模型.对三维有限元模型在垂直压缩、前屈、后伸、侧弯等不同载荷下进行生物力学分析,记录小关节的应力,并与正常运动节段三维有限元模型相应部位的应力进行对比.结果与结论:生物力学分析结果显示,人工椎间盘置换后:①垂直压缩时上下椎体、双侧小关节内应力与正常节段相比差异无显著性意义(P > 0.01).②前屈、后伸时上下椎体前、后方及双侧小关节内应力与正常节段相比差异无显著性意义(P > 0.01).③侧弯时上下椎体左右两侧及双侧小关节内应力与正常节段相比差异无显著性意义(P > 0.01).提示人工腰椎间盘置换后小关节应力可保持在正常运动节段的水平,人工腰椎间盘置换可以达到腰椎生物力学性能重建的目的.

Three-dimensional finite element analysis of the zygapophyseal joints following artificial lumbar disc replacement

BACKGROUND: With deepening of spinal biomechanics, artificial lumbar disc replacement is considered to be the optimal choice for treating degenerative lumbar disease. However, studies concerning biomechanics of artificial lumbar disc are insufficient. OBJECTIVE: To establish the three-dimensional (3-D) finite element model of artificial lumbar disc replacement and to explore the effects of artificial lumbar disc replacement on zygapophyseal joints using biomechanical analysis. METHODS: Based on normal 3-D finite element model of lumbar motion segment, L4-5 intervertebral disc, superior and inferior endplates were removed, and then, the model of SB-Charite Ⅲ disc prosthesis was added, which remained annular fibrosus and ligaments at L4-5 intervertebral space. Thus, 3-D finite element model of L4-5 segments artificial lumbar disc replacement was constructed. Biomechanical analysis of this model was processed under axial load, forward flexion, lateral bending or posterior extension moments. The stress data were contrasted with the normal 3-D finite element model of artificial disc replacement. RESULTS AND CONCLUSION: After artificial lumbar disc replacement, the data of biomechanical analysis indicated: ①There was no significant differences between the zygapophyseal joint and normal segment of stress under axial load (P > 0.01). ②Compared with normal segment, the stress of anterior, posterior of upper and lower vertebral body and bilateral zygapophyseal joint had no obviously difference under forward flexion and posterior extension moments (P > 0.01). ③The stress differences between the both sides of upper and lower vertebral body and bilateral zygapophyseal joint were not significant under lateral bending moment (P > 0.01). Artificial lumbar disc replacement can keep the stress of motion segment at normal level, which can meet the needs of spinal functional reestablishment.