A rare case of bilateral occipital condyle fractures associated with inferior clivus separation fracture resulting in craniocervical dislocation: a case report and modification of the Anderson and Montesano classification is proposed.

The authors report a very rare case of bilateral occipital condyle fractures (OCF) that was associated with complete separation fracture of the inferior clivus resulting in craniocervical dislocation alongside dissociation of C1-C2 joint complex. Also, a new type of the Anderson and Montesano classification system is presented with two subtypes of injuries. Type IVA occurs when the OCF is associated a clivus avulsion fracture, while Type IVB occurs when the OCF is associated with complete "en piece" separation fracture of the inferior clivus. Both Type IV injuries are considered highly unstable, and surgical fixation is the recommended treatment option.