Congenital absence of the posterior arch of the atlas with concomitant fusion to the axis: a case report.

We present a 52-year-old man with congenital absence of the posterior arch of the atlas and concomitant fusion of the posterior tubercle of the atlas to the spinal process of the axis. He had normal reflexes and no motor deficit. He underwent C3-C7 laminoplasty and achieved good outcome.