Subaxial sagittal alignment after atlantoaxial fixation techniques.

Abstract

A retrospective clinical case series. To evaluate the association between C1-C2 fixation angle and postoperative C2-C7 alignment in the sagittal plane after C1 lateral mass screw with C2 pedicle screw fixation (C1-LMS) or Magerl with wiring technique. Various techniques for posterior correction and fusion, such as the Magerl procedure with posterior wiring and C1-LMS procedures, are used for treating atlantoaxial instability. However, only few studies investigating the relationship between postoperative C1-C2 angle and C2-C7 sagittal alignment change after C1-C2 fixation have been reported. We retrospectively followed up 42 patients who underwent the C1-LMS (22 patients) or Magerl with wiring procedure (20 patients) to treat C1-C2 instability for >2 years. The atlantodental interval, space available for the spinal cord, and O-C1, C1-C2, C2-C3, and C2-C7 angles were measured. Significant reduction in atlantodental interval and increase in space available for the spinal cord were observed in both groups. Although the preoperative C1-C2 angles were similar, the angle at the final follow-up was higher in the Magerl with wiring group than in the C1-LMS group (P<0.01). The C1-C2 fixation and postoperative C2-C7 angles were negatively correlated in both groups (C1-LMS group, r=-0.55, P<0.01; Magerl with wiring, r=-0.62, P<0.01). Increased lordotic change in the C1-C2 angle was associated with increased kyphotic changes in the C2-C7 angle after both procedures. The C1-LMS procedure effectively controlled C1-C2 sagittal alignment during surgery. To decrease the risk of postoperative subaxial kyphotic changes, the C1-C2 fixation angle should be carefully determined.