【作者】 刘策；

【导师】 周定标； 余新光；

【作者基本信息】 中国人民解放军军医进修学院 ， 外科学， 2007， 博士

【摘要】 目的：研究先天性颅颈交界区畸形的解剖与形态学变化，了解不同个体骨性畸形的特征、寰枕融合时椎动脉的走行变化、寰枕融合时侧块关节的形态生物力学变化，以及颈椎2-3融合时螺钉内固定的适用性。方法：41例先天性颅颈交界区畸形患者，经螺旋CT扫描后，图像序列导入Amira影像工作站，构建枕骨-寰椎-枢椎的三维模型，通过对三维模型选择性显示、切割以及多角度旋转观察局部的解剖与形态特征，并完成相关解剖学测量。结果：先天性颅颈交界区畸形包含了复杂的枕骨、寰椎和枢椎的畸形。本组病例中以扁平颅底、颅底陷入、寰枕融合和颈椎2-3融合最为常见，部分病例也合并了一些特殊的畸形如单侧寰椎侧块过度肥大、枢椎椎板裂、枕骨髁旁突等。对骨性畸形的解剖观察显示，斜坡、枕骨髁、寰椎侧块、寰椎后弓的畸形伴有不同程度的发育不全，部分病例寰枕融合表现为明显的旋转性错位融合。三维可视化同步对比观察23例寰枕融合的局部骨性畸形与椎动脉的走行，提示寰椎和枕骨大孔周边结构不同程度的融合和发育不全，造成了椎动脉在该区域的走行发生多种变异。对35例寰枕融合畸形的寰椎下关节面的三维形态学观察显示，寰椎下关节面的前倾角和外倾角具有广泛的个体间差异，不同程度对称或不对称的下关节面前倾与不同形式的寰枢椎脱位具有一定相关性。对17例颈2-3融合畸形的枢椎关节间部和颈3椎弓根进行的局部解剖学测量显示，因关节间部和颈3椎弓根双侧狭窄而不适于3.5mm螺钉置入者分别见于1例和3例，因单侧狭窄不适于螺钉置入者分别见于4例和7例。结论：1．先天性颅颈交界区畸形的基本特征是枕骨、寰椎、枢椎在不同程度的发育不全基础上发生了不同程度和方式的畸形融合，因而不同个体存在各自的形态差异。寰枕融合时，椎动脉入颅方式存在多种变异，这些变异与骨性畸形有一定关系。外科医生需要对骨性畸形以及椎动脉的走行变异有足够的认识，以免手术中出现意外损伤。2．寰枕融合时寰枢椎之间承重关节常呈现不同程度的前倾和不对称，这种几何形态变化所导致的关节生物力学变化可能是寰枢椎脱位的重要原因。3．尽管先天性颈2-3融合解剖形态与正常颈2-3结构相异甚大，多数病例应用螺钉内固定技术仍然可行。更多还原

【Abstract】 Objective: To describe the anatomical and morphologic characteristics of the congenital craniovertebral junction (CVJ) malformation, including assessment of the discrepancies of bony anomalies, variations of the route of vertebral artery (VA) in the subgroup with occipitalization of the atlas, biomechanical diversities of atlantoaxial facet joints morphology of occipitalization of the atlas, and anatomical suitability of screw fixation for the subgroup with C2-3 fusion.Methods: 41 patients with congenital CVJ malformation were analyzed. After spiral CT scan, the image files in D1C0M format were transferred to the three-dimensional visualization workstation based on a set of Amira software. Three dimensional (3D) models of occipito-atlanto-axial complex were constructed. Anatomical and morphological evaluations were examined by selective display and cutting, arbitrary rotation of the 3D models in the virtual environment. Also the related measurements were made with respect to the selected landmarks.Results: The congenital CVJ malformation compromises anomalies form occiput, atlas and axis. In this series, often the malformed osseous architectures were different combinations of platybasia, basilar invagination, occipitalization of atlas, and C2-3 fusion. Several uncommon anomalies were also found in association, such as unilateral atlantal lateral mass hypertrophy, spina bifida of axis, and occipital paracondylar process. Detailed analysis of the bony anomalies suggested the concomitant dysplasia was common in anomalies of clivus, occipital condylar, atlantal lateral mass, and atlantal posterior arch. Occipitalization of atlas in some cases manifested rotated fusion, representing the rotated misalignment of atlas to occiput. Comparative observations of bonyanomalies and variations of the route of VA in 23 cases of occipitalization of atlas revealed that the VAs may take several discrete routes to enter the crania in respect of the varied extent of fusion and dysplasia between atlas and foramen magnum. In 35 cases of occipitalization of atlas, three dimensional morphometrics of atlantal inferior facet were carried out, showing a great scope of variation of facet angles both on the sagittal and coronal planes. Excessive anterior tilting and/or asymmetry of atlantal inferior facet may be in relation to the various types of atlantoaxial dislocation. Anatomical measurement of C2-3 fusion for evaluation of screw placement, which were performed in 17 cases of C2-3 fusion, demonstrated that narrowing of C2 pars interaticularis or C3 pedicle, which caused unsuitability for a 3.5mm screw placement, on both side was seen in one or 3 cases, on single side was seen in 4 or 7 cases, respectively.Conclusion: 1. The essential configuration of congenital CVJ malformation is the diversiform segmentation failure on the basis of the dysplasia to various extents in occiput, atlas and axis; hence the prevalence of individual discrepancy regarding the detail anatomy. In those patients where existed the occipitalization of atlas, several regular patterns of intracranial route of VA were found, which may or may not resemble the normal anatomy. These patterns were accompanied by some detailed variation of the bony malformation, and also further suggested some embryologic discrepancy in the formation process of the unsegmented occipito-axial structure. The surgeons should familiar to the bony and vascular variations in order to avoid the unexpected injuries such as the compromise of VA during a surgery. 2. Prevalence of anterior tilting and asymmetric articulations can be seen in the load-bearing joints of atlantoaxial complex in patients with occipitalization of atlas. The resulting biomechanical changes may be a more proximate cause for atlantoaxial dislocation in these patients. 3. Although quite a few morphological variations was seen in congenital C2-3 fusion, application of screw fixation techniques in this structure was still feasible in majority of the patients.更多还原