Complex atlas fracture with posterior dislocation of one lateral mass

An unusual fracture/dislocation of the atlas that defies classification is reported. Posterior dislocation of the left occipital condyle resulted in loss of articulation with the superior articular surface of the atlas. It could be considered a unilateral atlanto-occipital dislocation or possibly a Jefferson fracture variant. The patient suffered only a mild, temporary neurological deficit and was treated conservatively.