Modern treatment of the symptomatic os odontoideum.

A new surgical procedure for treatment of congenital, symptomatic atlanto-axial instability (os odontoideum ) is described. Two metallic clamps, with an integrated inner spring for maintaining continuous pressure on a cortico-cancellous bone-graft implanted into the interlaminar space, are fixed posteriorly on the vertebral arches C1/2 next to the graft. Because of the initial solid segment-stability external fixation is unnecessary. Posterior interlaminar osteosynthesis prevents late neurological complications caused by a mobile os odontoideum .