Anteroposterior spondyloschisis of the atlas. Two case reports and literature review.

Congenital bony defects of the atlas are uncommon; with isolated posterior clefts being the most frequent anomaly and combined anterior and posterior defects the least common, occurring in only 0.3-0.7% of the population. These anomalies can cause confusion, particularly in the setting of trauma when appearances on plain radiography may be misinterpreted as representing a fracture. Two cases of anteroposterior spondyloschisis are presented and the pathology, diagnosis and the clinical relevance of such defects discussed with reference to previous published literature.