Purpose
The purpose of this retrospective study was to evaluate the results and complications of lateral mass screw fixation on C7 in a single spinal center.
Materials and Methods
During a 7-year period, a total of 104 lateral mass screws were placed on C7 in 56 patients with cervical disorders. A review of the hospital records and radiographs of these patients was conducted. Followup plain X-rays and computed tomography (CT) including sagittal reconstruction were obtained to analyze screw positions.
Results
A total of 104 screws were placed on C7 lateral mass using the modified Magerl’s method. Most patients had two screws on both lateral masses, but eight underwent unilateral lateral mass screw fixation due to fracture (n=4), lateral mass deficit due to tumor removal (n=1), and unilateral fixation for additional stabilization of an anterior fixation (n=3). Most cases were connected to the subaxial spine (91.1%). All patients underwent more than 1 year of follow-up. The only complication was one wound infection. On follow-up CT, one transverse foramen invasion (2 mm), one spinal canal invasion, and four facet joint violations developed post-operatively. However, no symptoms related to these issues were occurred, so reoperations for instrument repositioning were not required. Screw loosening and pseudoarthrosis did not develop during the follow-up period. Also, there was no case of vertebral artery or neural injury requiring reoperation due to the position of the lateral mass screw. Almost patients showed successful bone fusion on follow-up images, with the exception of one patient.
Conclusion
Despite the small size of the lateral mass, risk of pseudoarthrosis, and steep angle of the lamina, lateral mass screw fixation can be a safe, easy and less complicated method of posterior cervical stabilization. If the lateral mass is suitable, lateral mass screw fixation may enable C7 stabilization during posterior subaxial cervical surgery.