SEGMENTAL FIXATION OF C1-C2 WITH DIRECT LATERAL MASS PLATE AND SCREW FIXATION

Introduction We review our experience with the use of plate and screw (C1 lateral mass and C2 pedicle) method of fixation in the treatment of 300 patients with disorders of the craniovertebral junction during a 17-year period at our center. We previously described this method of fixation in 1994. Methods Between 1988 and 2004, 250 patients with atlantoaxial instability were treated with the use of a plate and screw method of fixation at our institution. The various aetiologies of atlantoaxial instability were congenital, trauma and rheumatoid arthritis. All patients had mobile, completely reducible atlantoaxial subluxation. The male: female ratio was 3:1. C1 lateral mass screw and C2 pedicle screw were anchored to a plate bilaterally. For 3 months postoperatively, a hard cervical collar was used. The mean follow-up period was 42 months (range, 4 mo–17 yr). Recently, we have modified the technique by distracting the lateral facet joints, placing a cage bilaterally and then performing the lateral mass fixation for a subgroup of 50 patients with either fixed atlantoaxial joint subluxation or basilar invagination. Results Three patients died in the postoperative phase. Successful stabilization of the atlantoaxial region was documented with dynamic radiography in the other patients. In one patient, one screw was found to be broken 18 months after surgery; however, firm bony fusion was documented in this patient. There were no neurological, vascular, or infective complications. Discussion Segmental fixation of lateral masses with plate and screw method of fixation with the use of intra-articular bone grafts in patients with atlantoaxial instability yielded a 100% fusion rate with a low incidence of complications. Direct application of screws into the thick and large cortico-cancellous lateral masses of atlas and axis provides a biomechanically strong fixation of the region.