What is fusion or stabalization of atlas-axis or C1-C2?

C1-C2 or atlanto-axial fusion/stabilization is a procedure done for wide variety of C1-C2 pathology like odontoid fracture, C2 fracture, occiputo-C1 dissociation, os-odontoid, congenital C1-C2 dislocation, C1-C2 dislocation in rheumatoid arthritis etc. The procedure involves putting screws in C1 and C2 vertebra and the doing bony fusion between above vertebrae.