Lateral Mass Screw Fixation of the Atlas: Surgical Complications

Introduction: Lateral mass screw fixation of the atlas is an important technique to achieve immobilization and fusion in instability involving the atlas. It can be used for atlantoaxial segment or even for longer constructions involving the subaxial cervical spine. We reported the surgical complications of lateral mass screw fixation of the atlas. Methods: A retrospective evaluation of patients who had atlas instrumentation from January 2009 to July 2016 by the one of the authors (AFJ) was performed. Thirty-nine patients were surgically treated. Most cases were due to spinal trauma (28 patients – 76.9%), followed by congenital malformations (three patients – 7.69%), neoplastic disease (two patients – 5.1%), inflammatory conditions (two patients – 5.1%), degenerative cervical spine disease (one patient – 2.56%) and infection (one patient – 2.56%). The mean age was 41.3 years (ranging from 8 to 84 years old), with a mean follow up was 5 months. Results: Thirty-four patients (87.1%) were treated by atlantoaxial fusion, three (7.69%) cases underwent C1–C3 fixation, one underwent C1–C4 fusion, and one patient had an occipito-C2 fusion. The most common technique of C2 fixation was laminar screws (24 patients – 61.5%), followed by C2 pars screws (nine patients – 23%) and pedicle screws (two patients – 5.1%) cases. Combined techniques of atlantoaxial fusion (laminar + pedicle or laminar + pars) were used in five cases. Complications of the procedure related to C1 screw fixation occurred in six patients: three cases of important venous bleeding requiring blood transfusion but without hemodynamic complications, one case of condyle joint violation and postoperative pain for some weeks (without need to remove the screw), one case of medial violation of the lateral mass and finally one case of dural CSF leak treated with direct intraoperative repair. No neurological worsening or mortality was observed in these series related to the procedure, neither vertebral artery injury. Conclusions: Lateral mass screws for fixing the atlas is an important and efficient technique, mostly used for atlantoaxial fixation. Anatomical knowledge and meticulous surgical technique may improve the safety of the procedure.