寰枢椎脱位模型构建与后路动态软性固定系统治疗的可行性研究

Congenital atlanto-occipital fusion and C2-3 fusion are the most common two pathogeneses of atlanto-axial dislocation in Chinese population. Biomechanical tests showed that the atlanto-odontoid joint movement increased most in flexion after atlanto-occipital joint fixation. However, no related biomechanical study emerged concerning the pathogenesis of atlanto-axial dislocation from combined atlanto-occipital fusion and C2-3 fusion yet. Atlanto-axial fixation and fusion is still the standard and effective treatment for atlanto-axial dislocation. However, the important physiological atlanto-axial rotatory movement is lost after any kind of atlanto-axial fusion, and the adjacent segment degeneration may occur in lower cervical spine after fusion. The non-fusion dynamic stabilization systems were recently developed to treat some lumbar degenerative diseases. Related biomechanical researches about the posterior dynamic stabilization system especially those soft instrumentations like Dynesys showed that: flexion motion was the most limited, and axial rotation was the least limited, after device implantation. However, no report emerged concerning the treatment of atlanto-axial dislocation using Dynesys system. We hypothesize that the range of flexion motion of atlanto-odontoid joint would be more greatly increased after atlanto-occipital fusion and C2-3 fusion, this may lead to subsequent atlanto-axial dislocation. The dynamic Dynesys soft stabilization system may be effective in restraining the flexion motion of atlanto-axial joint while preserving partial motions in rotation and other directions, hence achieve the dynamic atlanto-axial stabilization, and prevent subsequent atlanto-axial dislocation. By combining the fine element model analysis and the cadaveric biomechanical study, we are trying to testify our hypothesis. Our research is supposed to provide a novel, effective approach in the treatment of atlanto-axial dislocation.

先天性寰枕融合与C2-3融合是造成国人寰枢椎脱位的主要因素。人为固定寰枕关节，寰枢椎屈曲运动范围显著增加，易继发寰枢椎脱位。但尚无对寰枕融合并C2-3融合后寰枢椎脱位发病机制的研究。寰枢椎内固定融合术是治疗寰枢椎脱位的标准术式，虽疗效肯定，但术后寰枢椎活动度完全丧失，对下颈椎亦可能产生不良影响。研究表明，作为非融合技术, 以Dynesys系统为代表的动态软性固定主要限制脊柱屈曲活动，但尚未有用其治疗寰枢椎脱位的研究报道。课题组推测，在人为固定寰枕关节及C2-3后，寰枢椎屈曲活动增加更为明显，更易继发寰枢椎脱位。而将Dynesys系统改良，去除螺钉间垫片，仅保留人工韧带，以固定寰枢椎，可以明显限制寰枢椎屈曲活动，实现寰枢椎的动态稳定，有效防止寰枢椎脱位。本课题组拟通过有限元分析与尸体标本生物力学研究相结合的方法，系统性的对以上假设进行验证，从而为临床治疗寰枢椎脱位提供新的思路并奠定理论基础。

先天性寰枕融合与C2-3融合是造成国人寰枢椎不稳或脱位的主要因素。当以上两种病理因素并存时，上颈椎活动仅存在于寰枢椎之间，从而可能导致寰枢椎运动尤其是屈曲运动范围代偿性显著增加，进而易继发寰枢椎不稳或脱位。但目前尚无对寰枕融合并C2-3融合后寰枢椎继发不稳或脱位具体发病机制的深入研究。另一方面，虽然寰枢椎内固定融合术是目前治疗寰枢椎不稳及脱位的标准术式，但该术式导致寰枢椎活动度完全丧失，而且对下颈椎亦可能产生不良影响。研究表明，作为非融合技术, 以Dynesys系统为代表的动态软性固定主要限制脊柱屈曲活动，可能弥补传统固定融合术式的不足，但目前尚未有用其治疗寰枢椎不稳的研究报道。本课题组通过有限元分析与尸体标本生物力学研究相结合的方法，系统性的进行相关研究。首先成功建立了寰枕融合及C2-3融合伴寰枢椎不稳的有限元模型，继而在此模型上加载传统后路寰枢椎钉棒内固定系统及改良Dynesys动态固定系统（去除Dynesys系统连接螺钉间的垫片，仅保留人工韧带，以固定寰枢椎），分析其生物力学特点，并通过尸体标本的生物力学实验对有限元分析的结果进行印证，研究结果证明：改良Dynesy动态固定系统可有效限制寰枢椎不稳状态下，寰枢椎间的前屈运动，从而实现寰枢椎不稳的有效动态稳定；同时，该系统可以很大程度保留寰枢椎间后伸运动功能，并部分保留寰枢椎轴向旋转和侧弯运动功能，该方面和传统刚性钉棒内固定系统相比具有一定的优势。该实验结果为临床治疗寰枢椎脱位提供了新的思路并奠定了相关理论基础。