Morphological changes of the atlantoaxial facet joint and three-dimensional characteristics of atlantoaxial dislocation in patients with atlanto-occipital assimilation / 中华神经医学杂志

ABSTRACT

Objective To explore the morphological changes of the atlantoaxial facet joint and the three-dimensional characteristics of joint dislocation in patients with atlanto-occipital assimilation accompanied by atlantoaxial dislocation. Methods Thirty-six patients with atlanto-occipital assimilation and concurrent atlantoaxial dislocation underwent spiral CT scanning of the craniovertebral junction, and the imaging data in DICOM format were transferred to the three-dimensional visualization workstation to construct the three-dimensional model of the craniovertebral junction. The characteristics of atlantoaxial dislocation in association with the bony malformation were studied in the reconstructed model. Results Multiple anomalies of the atlantoaxiai facet joint were found in these patients, including joint dislocation involving 57 sides in the 36 patients, skeletal deformity in 61 sides, and facet separation in 11 sides. Three-dimensional classification identified 3 types of atlantoaxial dislocation in these patients, namely symmetrical type (14 cases, 39%) representing the approximately symmetrical joint dislocation and/or skeletal distortion, rotational type (13 cases, 36%) representing apparently asymmetrical joint dislocation and/or skeletal deformity, and separate type (9 cases, 25%) with separation of the joint facets. Conclusion In patients with atlanto-occipital assimilation, multiple factors including developmental anomaly, secondary skeletal deformity and ligament extension and fatigue interact as the fundamental causes ofatlantoaxial dislocation. The CT-based three-dimensional model of the craniovertebrai junction allows visualization of the atlantoaxial facet joint and atlantoaxial dislocation to provide important evidence for surgical planning and decision on the internal fixation approaches.