POSTERIOR OCCIPITOAXIAL FUSION FOR ATLANTOAXIAL DISLOCATION ASSOCIATED WITH OCCIPITALIZED ATLAS

Between 1989 and 1994, 50 patients suffering from congenital atlantoax ial dislocation with either an assimilated atlas or a thin or deficien t posterior arch of the atlas were treated with occipitocervical fusio n using the technique described by Jain and colleagues in 1993 with a few modifications. An artificial bridge created from the occipital bon e along the margin of the foramen magnum was fused to the axis using s ublaminar wiring and interposed strut and lateral onlay bone grafts. T en patients (20%) also underwent atlantoaxial lateral joint fusion by intraarticular instillation of bone chips. In 22 patients (44%) with i rreducible dislocation, posterior fusion was preceded by transoral odo ntoidectomy. In seven patients (14%) with ventral compression, who sho wed marked clinical improvement on traction despite radiological evide nce of persisting atlantoaxial dislocation, occipitocervical fusion wa s performed without ventral decompression. Seven patients (14%) underw ent a single-stage transoral odontoidectomy and posterior fusion. Ther e was no perioperative mortality and the osseous fusion rate was 88%. Of the 43 patients available at follow-up examination (range 3-12 mont hs), 31 patients (72.09%) improved, seven (16.28%) remained the same, and five (11.6%) deteriorated in comparison with their preoperative st atus. Hence, this technique achieves a stable occipitocervical arthrod esis without supplemental external orthoses and facilitates early post operative mobilization.