颈椎间盘置换术后相邻节段退变的生物力学机制

Cervical diseases badly affect the quality of life for the individuals with disc degeneration. As an alternative to anterior cervical discectomy and fusion (ACDF), artificial disc replacement (ADR) are one of the main surgical treatment for disc degenerative diseases. However, the incidence of adjacent segment disease requiring additional surgery after ADR is not significantly different with ACDF. One interpretation of these clinical results is that the motion that is retained following ADR or ACDF does not adequately replicate in vivo motion, resulting in altered loading of adjacent segment. In order to assess the extent to which ACDF and ADR affect the operated and adjacent segments, reference data for the healthy cervical spine is necessary. The range of motion (ROM) is the most studied parameter concerning spinal kinematics. The intervertebral center of rotation (ICR) of the cervical spine has been rarely investigated, since the determination of ICR has been a major problem because of the complex cervical motions. Finite element analysis (FEA) is one of the main methods investigating cervical biomechanics. However, the ICR were absence in validation or investigation in the reported FEA models in literatures. There is also lack of biomechanical understanding within the degenerative cervical spine. This proposed project aims to combine in vivo and in vitro biomechanical experimental and computational methods, 1) to understand kinematics of cervical spine, especially the ICR, 2) to develop a FE model that can replicate the realistic cervical kinematics, especially reproduce the ICR, and to investigate the effects of disc degeneration and ADR on cervical biomechanics. This study can improve understanding of cervical biomechanical environment, be benefit to the clinician in guiding the surgery and developing new artificial disc that can replicate in vivo motion.

间盘退变引起的颈椎疾病严重影响病人生活质量。作为椎间融合手术的替代方案，间盘置换并未能显著改善相邻节段间盘退变（ASD）的发生率。ASD可能与置换术后颈椎运动特征改变所引起的周围组织力学环境变化相关。椎间活动范围（ROM）和旋转中心（ICR）与颈椎运动密切相关，分别反映椎间活动的程度与方式。目前，间盘置换对ROM的影响已有大量研究；而因颈椎活动复杂，测量ICR存在困难，关于置换对ICR分布的影响的认识还不充分。本项目拟：1）应用双平面X射线动态成像技术重建颈椎的在体运动，结合离体实验和有限元分析，深入研究颈椎的运动特征，特别包括ICR分布；2）构建反映在体运动特征的颈椎有限元模型，研究间盘退变与间盘置换对颈椎力学环境的影响，探索置换术后发生ASD的力学机制。本研究可增加对颈椎运动特征的认识，为研发重建生理运动的新型人工间盘提供理论基础；可以预测手术疗效与风险因素，具有临床指导意义。

作为椎间融合手术的替代方案，间盘置换(CDR)并未能显著改善相邻节段间盘退变（ASD）的发生率。ASD可能与置换术后颈椎运动特征改变所引起的周围组织力学环境变化相关。椎间活动范围（ROM）和旋转中心（ICR）与颈椎运动密切相关，分别反映椎间活动的程度与方式。因颈椎活动复杂，并且ICR的测量存在一定的难度，关于置换对ICR分布的影响的认识还不充分。本项目结合在体、离体标本和有限元建模分析，研究了正常颈椎的运动特征和间盘退变对颈椎运动特征的影响，并对多种具有不同构型的人工间盘进行置换的模拟，探索置换术后发生ASD的力学机制。研究表明，正常颈椎的椎间ICR分布在不同节段存在区别的，提示各节段应该采用差异化的人工间盘设计；间盘退变将导致ICR的分布重心向前、向上平移；间盘置换节段的椎间ICR分布较为分散，且间盘之间存在较大差异；每个椎间盘假体均具有其生物力学优点和缺点，应当基于患者个体差异和具体情况进行选择。本研究可增加对颈椎运动特征的认识，为研发重建生理运动的新型人工间盘提供理论基础；可以预测手术疗效与风险因素，具有临床指导意义。