The Malformation Of Lateral Atlantoaxial Articulation In Basilar Invagination And It’s Stability Analysis

Objectives To perform three dimensional structure description, functional analysis andclinical classification of lateral atlantoaxial articulation. To explore the relationshipbetween the malformation of lateral atlantoaxial articulation and atlantoaxial articulationstability.Methods The clinical data was analysed both in20cases of heathy adult and60casesof congenital or developmental anomalies of the basilar invagination; Measurements ofthe obliquity of atlantoaxial articular facet was performed between the facet and the newhorizontal line, The morphological variation of the lateral atlantoaxial articulation wasstudied and the atlantoaxial dislocation and clinical symptoms was summarized.Results The normal articular facet of lateral atlantoaxial articulation was flat withoutobvious obliquity. The deformed configuration of lateral atlantoaxial articulation wasdefined to four types. Type I, characterized by slight anteversion of lateral atlantoaxialarticulation without olisthy of the inferior and superior facets, angle of inclination is16.4±4.5°; Type II, defined by the separation or complete olisthy of the two facets, angle ofinclination is38.3±13.7°; Type III, wherein the articular facets sloped dorsally, angle ofinclination is14.5±10.5°; Type IV, complex abnormality, including the lateral jointdislocation, rotating, pseudarthrosis formation, etc. The degree of the anteversion oflateral atlantoaxial articulation has negative correlation with the age of initial presence ofthe clinical manifestation and positive correlation with the clinical symptoms in type I, II.Conclusion Instability at the C1-C2junction in congenital and developmental anomalyof basilar invagination is likely a direct result of the anteversion and structural variationof lateral atlantoaxial articulation, and it aggratates with the increasing obliquity ofanteversion of the articular facet. Demonstrating the malformation and clinical typing oflateral atlantoaxial articulation provides a new means to diagnosis instability incongenital anomaly at basilar invagination and provide insight into the pathogenesis ofbasilar invagination and a basis for rational surgical treatment.