Plate and screw fixation for atlanto-axial subluxation.

Our experience with 30 cases of atlanto-axial dislocation, over the period of 3 years and 9 months, is described. A modified plate and screw method of fixation of the lateral masses of the atlas and axis was successfully used in these cases. The technical aspects and merits of the method, wherein a 100% union rate was achieved, with no morbidity, mortality, or instrument fatigue or failure, are presented. The average follow-up period is of 19 months. The technique provided immediate rigid segmental internal fixation, permitting early mobilization with minimal external support. Onlay and interfacetal bone grafts subsequently produced bony fusion. Direct application of screws to the atlas and axis, thus utilizing the firm purchase in their thick and large cortico-cancellous lateral mass, provides a biomechanically strong fixation of the region. Occipito-cervical fusion can be achieved in selected cases by a modification of the method. It appears that such a method of fixation could be useful at least in some complex congenital or traumatic craniovertebral region instability where the conventional methods have failed or are not suitable.