Athletic cervical spine injury in the setting of fusion failure of the anterior and posterior atlas.

This article describes a rare congenital abnormality of anterior and posterior C1 fusion failure presenting after an acute athletic injury to the fibrous nonunion. C1 congenital malformations are rare, occurring in approximately 2% of patients; even rarer are combined anterior and posterior arch malformations in the same patient. Posterior ring abnormalities are more common than anterior ring injuries (4.5:1, respectively). To the authors' knowledge, combined anterior and posterior ring congenital malformations with subsequent injury have not been previously described. In the current patient, a congenital failure of fusion of the anterior and posterior arches of C1 was identified. The anterior fibrous nonunion was injured while the patient played football, leading to transient neurologic injury and dysphagia from soft tissue swelling. The patient was initially diagnosed with an acute fracture at another facility; however, given advanced imaging, flexion and extension views, and a normal neurologic examination, the authors diagnosed a traumatized congenital defect. The injury healed with a short period of cervical collar immobilization and supportive measures. Such malformations are usually found incidentally, but they can be symptomatic after trauma. Images to distinguish these deficits can be difficult because the differences between chronic nonunions and congenital malformations are subtle. Surgery is rarely indicated for congenital malformations because they are often stable even after injury; however, they may predispose patients to neurologic injury in the future with high-risk activities. Because the current patient had an increased chance of future injury secondary to the lack of bone formation in the C1 vertebrae, he was restricted from participating in contact sports.