Mobile and reducible atlantoaxial dislocation in presence of occipitalized atlas - Report on treatment of eight cases by direct lateral mass plate and screw fixation

Study Design. This is a retrospective review on the application of the authors' technique of atlantoaxial lateral mass plate and screw fixation on a rare subset of patients having mobile and reducible atlantoaxial subluxation in the presence of occipitalized atlas. Objective. Mobile and reducible atlantoaxial dislocation in the presence of an occipitalized atlas is extremely rare. We retrospectively analyzed the management of eight such patients who were treated by lateral mass plate and screw fixation. Summary of Background Data. The authors report their experience with a rare congenital craniovertebral anomaly where there was a mobile and reducible atlantoaxial dislocation in the presence of the occipitalized atlas. The cases were treated by lateral mass plate and screw method of treatment described by the authors in 1994. Methods. Eight patients with occipitalized atlas had a mobile and completely reducible atlantoaxial dislocation. These patients were treated between the years 1996 to 2003 and underwent a direct atlantoaxial lateral mass fixation. The follow-up ranges from 4 months to 6 years ( average, 48 months). Results. All patients underwent a successful fixation and ultimately achieved a solid bony fusion. There were no intraoperative or postoperative complications. Conclusions. Although lateral mass plate and screw fixation in the presence of occipitalized atlas is technically a relatively difficult and anatomically a precise surgical procedure, the firm and segmental stabilization that it provides offers an optimum situation for bony fusion.